Despite the common perception that Canada has an unlimited supply of fresh water, the reality is that our water resources are under stress. Demand for water is rising because the population is increasing, lifestyles are changing, and the impacts of a changing climate are becoming clearer. Canadians are some of the highest per capita users of water in the world. According to Environment Canada’s “Freshwater Website”, simple changes to water use habits and domestic equipment can reduce water consumption in the home by up to 40%. There are many measures and strategies that can make a significant contribution to reducing water use. Some are quite common, simple, and inexpensive, whereas others are relatively new or ground-breaking. One that fits into this latter category is greywater reuse.

Many environmental agencies favour a “twin track” approach; that is, developing resources and managing demand. Exploring ways to reduce demand for municipal potable water is essential to ensure a sustainable future for water resources. One of the options is to install greywater systems as a substitute for potable water for purposes where drinking water quality is not required.

Although wastewater does eventually make its way back into the earth where it may be once again captured, treated, and distributed for potable use, it may be more beneficial to intercept it at its source, treat it, and use it in ways that don’t require it to be clean, pure, potable water. This reduces the demand for supplying more clean, fresh water for a growing population.

This learning module will describe how water from household fixtures may be reused for non-potable purposes such as flushing toilets and irrigating lawns and gardens.

Greywater versus Blackwater

Both greywater and blackwater are types of wastewater. Greywater is used water sourced from bathtubs, showers, bathroom basins and laundries. It is wastewater that can contain some soap, salts, hair, suspended solids, and bacteria, but that is clean enough to water plants. Although wastewater from kitchen sinks and dishwashers doesn’t contain fecal matter and is sometimes categorized as greywater (e.g., the kitchen sink discharge from a recreational vehicle), the high levels of organic materials such as oils and fats put them in the category of blackwater. Greywater (treated or untreated) is not the same as recycled water, which is highly treated wastewater from a centralized treatment facility.

Blackwater contains feces and urine and other bodily wastes from toilets, urinals, and bidets. Blackwater, therefore, needs more intensive treatment to kill any disease-carrying bacteria that may be present if it is desired to be recycled. This is beyond the scope and capabilities of most residential installations and therefore should not be attempted in a residential situation.

On the other hand, greywater can be recycled as its bacterial count, including the presence of pathogens, is much lower than blackwater. Greywater may be re-used for low-risk purposes, such as the flushing of toilets and urinals, and subsurface irrigation of lawns and ornamental gardens.

Benefits of Greywater Reuse

Reusing greywater from laundry, bathroom, and wash basin sources in urban households for garden watering/ irrigation, toilet flushing and laundry washing applications can on average reduce potable water demand by 41%, and this can vary from 30% – 70% (“Evolution of Water Recycling in Australian Cities Since 2003”, J. C. Radcliffe). Recycling greywater not only reduces the consumption of potable water, but it also reduces the volume of water discharged into the sewerage system. Less water going through a water meter translates to money saved on water bills. Beside that, there are many ecological benefits to greywater recycling. These can be summarized as follows:

• Lowering freshwater use – Greywater can replace fresh water in many instances, saving money on a regional level and increasing the effective water supply in regions where irrigation is needed. Residential water use in many regions is almost evenly split between indoor and outdoor purposes. With proper treatment, all except toilet and kitchen water could be recycled outdoors, achieving the same result with significantly less water diverted from nature.
• Less strain on septic tank or treatment plant – Greywater use greatly extends the useful life and capacity of septic systems due simply to the reduced volumes entering the tank or treatment plant. Less volume entering the plant means higher treatment effectiveness and lower treatment costs.
• Less energy and chemical use – Less energy and chemicals are used due to the reduced amount of both freshwater and wastewater that needs pumping on the upstream end and treatment on the downstream end. For those providing their own water or electricity, the advantage of a reduced burden on the infrastructure is felt directly. Also, for homeowners, treating their wastewater for use in the soil under their own fruit trees is a definite encouragement to dump fewer toxic chemicals down their drains.
• Highly effective purification – Greywater is purified to a high degree in the upper, most biologically active region of the soil, much the same as occurs in a septic field. This protects the quality of natural surface and ground waters.
• Groundwater recharge – Greywater application in excess of plant needs recharges groundwater levels.
• Plant growth – Greywater enables a landscape to flourish where potable water may not otherwise be available to support much plant growth.
• Reclamation of otherwise wasted nutrients – Loss of nutrients through wastewater disposal in rivers or oceans is a subtle, but highly significant form of erosion. Reclaiming nutrients in grey water helps to maintain the fertility of the land.

Using Greywater for Irrigation

Owners of greywater systems need to be aware of potential environmental impacts related to grey water system maintenance and household habits, with particular attention to chemicals used in the home, such as cleaning products and laundry detergents. Some important points to consider when disposing of greywater onsite are:

• Runoff of greywater from the property is not allowed and must be avoided. The escape of greywater onto public property would contravene health safety regulations. Properly manage grey water so it doesn’t flow into the street, neighbouring properties, or down storm drains.

• Greywater to be used for irrigation must be discharged below ground to reduce the risk of human contact. Although prohibited by plumbing codes, surface discharge of grey water in the garden is possible by manual bucketing. Bucketing is a simple method to collect grey water directly from the bathroom and laundry and apply evenly on garden or lawn areas. If bucketing, consider the following suggestions:

• • Post warning signs to property users that the plants are surface irrigated with greywater (e.g., “avoid contact”)
  • Apply greywater evenly to prevent ponding
  • For laundry water, select garden-friendly detergents that are biodegradable and low in phosphorus, boron, sodium, and chlorine
  • Avoid watering vegetables or fruit that are intended for raw consumption
  • Don’t apply greywater in areas which are readily accessible to children, pets, or immunocompromised people
  • Don’t reuse greywater when a household resident is sick (diarrhea, etc.)
  • Don’t reuse greywater which contains cleaning products, hair dye, or other chemicals such as paint, etc.

Using Greywater for Flushing

Although decreasing in its volume due to the advent of ultra-low consumption flushing technologies, it has been approximated that toilet flushing alone can account for anywhere between 10 to 35 percent of household potable water usage, so any reductions to this can amount to personal savings and greater resource conservation. Greywater flushing systems reuse wastewater from bathroom basins, bathtubs, showers, and clothes washers to substitute for toilet freshwater usage. The plumbing behind these systems can be simple enough but there are some practical and financial considerations to note before embarking on a greywater flushing project. A system that reuses greywater for irrigation may not require any treatment at all, whereas one used for toilet flushing will have many more requirements/constraints placed upon it, such as storage, filtration, disinfection, pressurization, labeling, and permits/inspections. Consequently, greywater reuse systems are more likely to be utilized for irrigation purposes only.

Health concerns

While gray water has low amounts of organic matter compared to other types of wastewater, it is not clean water, so exposure could be unsafe to humans. The microbial content in untreated gray water can thrive, potentially spreading bacterial sicknesses and disease to anyone who encounters it. These potential risks are the basis for strict regulations regarding water reuse and system installation, particularly for greywater use within the home. A greywater project that uses improper plumbing connections or ignores local regulations can potentially result in sickness as well as damage and lowered value to a home. Installing filters and disinfection measures within a greywater collection and storage system minimizes health risks and buildup of system impurities.

Storage and treatment

If a greywater system is other than a “laundry-to-landscape” type (covered later), the collected greywater will need to be stored and treated. This involves space, electrical, and chemical needs as well as constant monitoring by either manual or automatic means. Treated grey water can be stored for longer than 24 hours, whereas untreated grey water should be used as soon as possible and not stored. All grey water diversion and grey water treatment systems must be approved by the local authority and should be installed by a licensed plumber.

Backflow and cross connections

Of paramount importance is to ensure that there is no ability for greywater to enter the building’s potable water system through backflow or improper connections. Again, qualified installers such as licensed plumbers need to be involved in any greywater system installation.

Developing a Greywater Irrigation System

Greywater source

Chances are that a household will produce more gray water than it can use, so one must be selective about which drains will be sources for a greywater system and how they are connected. There is an abundance of online help to make water usage calculations that will prevent long-term storage of unneeded gray water. Sources such as bathtubs and clothes washers may produce more consistent wastewater amounts and quality than bathroom basins. Diverters to the regular drainage system, such as 3-way valves, should be included to provide the option of not collecting gray water when it may be in excessive amounts or hold potential contaminants.

Greywater characteristics and volumes

Although an ideal target would be to recycle 100% of the greywater that enters a residential drainage system, it has been found that, depending on regions and individual usage practices, approximately 50% to 80% of it can be recycled. Deciding which type of treatment system to implement varies based on such factors as the size of the dwelling, the volume of wastewater generated, regional climate, personal habits, and desired use of the finished recycled water. For instance, a greywater system designed for a rural farmhouse may have different components, recycling options and end uses than would a small townhouse with no landscaping needs in a city.

Greywater from clothes washers may contain high levels of sodium, carbonates, boron, and phosphates, which may have long-term effects on plants or soils.

Greywater systems can range from the very simple to the very complicated so it’s important to develop a systematic analysis of the proposed installation. This involves investigating a few fundamental concepts that should lead to the creation of a well-functioning and safe system.

Conversations with local equipment suppliers, installation contractors and current users is the most economical and environmentally friendly place to begin. It may be discovered that the current landscape doesn’t require as much water as it’s been getting, or that there are easy ways to greatly reduce the amount of water a household uses.

Determine which fixtures in the home are candidates for greywater capture. Washing machines are usually the easiest place to begin. If the clothes washer is in a room with an exterior wall, it’s usually simple to pipe the discharge to the outside. If the machine is in an interior room, it will be a little more difficult, but piping can be run through either a crawl space or basement.

Another potential fixture for greywater capture is a shower/bathtub. Even though there may be trace amounts of fecal matter present, it is usually of such a low concentration and occurrence that it is not a factor, and bath/shower water can be considered a source of greywater.

To develop a greywater system, consider these points:

1. Estimate the quantity of greywater your chosen source produces.
2. Analyze how water drains on the site. Determine the soil type using an onsite test, such as a “soil ribbon test” and/or a low-cost laboratory analysis (required if your system needs a permit). In combination with flow calculations, this analysis will help determine how large the landscape distribution area will need to be.
3. Research types of greywater systems and decide which is best for the site. The flow chart below is a list of types of systems in order of increasing complexity and cost (descriptions of these systems is found further along in this package).
   Laundry-to-landscape → Branched drain → Pumped system → Manufactured system → Sand filter-to-drip irrigation

   If a laundry-to-landscape system is chosen, the only fixture used for greywater collection will be the clothes washer. Branched drain, pumped, and manufactured systems normally utilize clothes washers and can also incorporate showers, bathtubs, and bathroom basins for collection. Sand filter-to-drip irrigation systems are typically only used where high greywater volumes are expected.

4. Consult the AHJ regarding any setback requirements to determine a system layout.
5. Draw a sketch of the proposed system. If a permit is required, a plot plan and details about the system will need to be submitted.
6. Once installed, make sure the system is properly labeled and provide an operation and maintenance manual with it. If the home is sold, the manual must stay with the residence.

Sizing the Greywater System

There are three steps to sizing a greywater system. It is important to follow these steps so that the system has adequate landscape distribution. Remember, local bylaws will require that greywater irrigation systems never cause pooling or runoff.

• Estimate greywater flows. There are different methods for estimating greywater flows based on whether the system requires a permit.
• Estimate the absorption capacity of soils based on the methods discussed earlier.
• Use greywater flow calculations and the soil absorption estimate to calculate the necessary size of mulch (irrigation) basins.

Estimating greywater flows

This can prove to be a complicated endeavour. There are a few different methods that rely on historical water usage, and these are probably the easiest and most reliable means available. Otherwise, records of water use (if available) and estimates of local daily per-person interior water usage are also acceptable sources of information.

Default Code Method

Some codes contain methods for estimating greywater amounts. The following information is published in the Uniform Plumbing Code for the State of Nevada.

1503.8.1 Single Family Dwellings and Multi-Family Dwellings

1.  The number of occupants in your household must be calculated as:
   • 2 occupants in the first bedroom
   • 1 occupant in each additional bedroom.
2. Greywater flows must be calculated as follows:
   • Showers, bathtubs, and washbasins (combined): 25 US gallons (95L) per day/occupant
   • Washing machines: 15 US gallons (57L) per day/occupant
3. Multiply the number of occupants by the estimated greywater flow per occupant to calculate the total estimated daily greywater flow.

Example greywater flow estimate using the Default Code Method

In a three-bedroom home, the following volumes of greywater would be estimated to be:

• Number of occupants = four (the three-bedroom home would have four occupants using the calculation method above)
• Shower/bathtub/basin greywater: 25 gpd (95 lpd) × 4 people = 100 US gpd (380 lpd)
• Washing machine greywater: 15 US gpd (57 lpd) × 4 people= 60 US gpd (228 lpd)
• Total greywater produced: 160 US gpd (608 lpd)

The above method can be used for any of the systems.

Another method, outlined below, can be used for laundry-to-landscape irrigation systems.

Irrigation supply calculation method

Irrigation supply calculations can also be used instead of the permitted systems method to size the landscape distribution area for systems that do not require a permit. Hence, they can only be used to size the landscape distribution area for laundry-to-landscape systems.

• Washing machines (weekly flow):               US gallons (litres)/load (the rating of your machine) ×               loads per week =               US gallons (litres) per week.
• Washing machines (daily flow):               US gallons (litres)/load (the rating of your machine) ×               loads on a typical laundry day =               US gallons (litres) per typical laundry day.
• Showers:               US gallons per minute (litres/sec)(the flow rate of your showerhead) ×               minutes taken for a typical shower ×               showers per day × actual number of home occupants = US gallons (litres) per day.

Note that if higher amounts of greywater are produced in a single day, (e.g., multiple baths or loads of laundry) you’ll need to consider this when designing the system. Situations where atypical amounts of greywater are produced in one day will also need to be considered. For instance, if five loads of laundry are sometimes produced in one day, rather than spreading them out over the week, this will need to be factored in when the system is designed and operated.

In cases of high flows, one option is to redirect the laundry water to the sanitary system using a 3-way valve. Remember that the system must be designed and operated to avoid greywater pooling and runoff.

Note that performing calculations for specific household fixtures yields the most accurate estimate of the amount of graywater available for plants, yet it does not consider future changes. Volumes could vary if the size or habits of a household change over time or if a new owner moves in.

Example estimation of greywater produced using the irrigation supply calculation method

In a three bedroom, three-person household with a laundry-to-landscape system, each person takes an 8-minute shower @ 2 US gpm (7.6 lpm) every day, each person does one load of washing a week, plus there is an extra load for towels, totaling four loads per week. Washing machine use is spread out across the week, sometimes two loads of laundry in one day. The household’s frontloading washing machine is rated at 20 US gallons (76 L) per load.

• Washing machine greywater (weekly flow): 4 loads per week × 20 USG (76 L) per load = 80 USG (302 L) per week
• Washing machine greywater (daily flow): 2 loads per day × 20 USG (76 L) per load = 40 USG (151 L) per day
• Shower greywater: 2.0 gpm (7.6 lpm) × 8 minutes/person per day × 3 people = 48 USG (181 L) per day
• Totals:
  

  Totals per week

  Washing machine	80 USG (302 L)
  Showers	336 USG (1,270 L)
  Total	416 USG (1,572 L)

  Totals per day

  Washing machine	40 USG (151 L)
  Showers	48 USG (181 L)
  Total	88 USG (332 L)

The irrigation system would have to be able to accommodate these amounts to prevent pooling and runoff. Information on irrigation system sizing is covered in a subsequent section of this module.

Greywater Regulations

The regulations for greywater reuse will differ between locales. Areas with regular drought problems are likely to encourage greywater systems, whereas some will prohibit their use. Local codes and regulations must be researched to determine what type of permit, inspection or monitoring is needed before installing a site constructed greywater system.

Technically, under the British Columbia Sewerage System Regulation, greywater is considered sewage, and discharging it onto land, into a source of drinking water, surface water, or tidal waters is considered a health hazard and is prohibited. All domestic sewage originating from a building must go into a public sewer or a sewerage system unless otherwise authorized under the prevailing edition of the BC Building Code. The 2018 BC Building Code, Part 7 Plumbing Services and the National Plumbing Code of Canada allow for the construction of non-potable water systems and subsurface irrigation using non-potable water. The “Health Canada Guidelines for Domestic Reclaimed Water for use in Toilet and Urinal Flushing” publication provides further guidance for greywater systems and is also referenced in the codes. Like in rainwater collection systems, the National and BC Plumbing Codes specify the use of “good engineering practice” in the design of a greywater reuse system and cite ASHRAE and ASPE Handbooks and CAN/CSA-B128.1 “Design and Installation of Non-Potable Water Systems” as resources. The plumbing codes only allow greywater systems to be used for the flushing of toilets and urinals, and for sub-surface irrigation. Any other use is not allowed.

The NSF/ANSI 350 (National Sanitation Foundation/ American National Standards Institute) standard establishes material, design, construction, and performance requirements for onsite residential and commercial water reuse treatment systems. They also set water quality requirements for the reduction of chemical and microbiological contaminants for non-potable water use. In North America many states and provinces provide greywater regulations that are continually changing, allowing for lower-cost greywater systems to be installed. Some of these areas may or may not require a permit for the installation. Always consult the AHJ to determine if a permit is required for a system and any setback requirements for such systems on a property.

Sample Regulation

The following sample is a current regulation from a major US city showing where an installation permit is and is not required.

When a permit is not required

A greywater system for outdoor irrigation may be installed without a permit if the following requirements are met:

• greywater comes from the washing machine only.
• greywater system does not alter the household plumbing (greywater is accessed from the hose of the machine, not by cutting into the plumbing).
• greywater system is for a one- or two-unit residential building.
• greywater system follows all guidelines set forth in the prevailing plumbing code

When a permit is required

A permit is required for a greywater system for outdoor irrigation that includes any of the following conditions:

• a greywater system collects water from showers, sinks, or baths.
• a greywater system alters the plumbing (the drainage plumbing is cut into to access the greywater).
• a greywater system is installed in a building that is not a one- or two-unit residential building.
• a greywater system includes a pump (excluding the washing machine internal pump) or a tank.

Now complete Self-Test 8 and check your answers.

Self-Test 8

Irrigation Using Greywater

An essential component of most greywater systems, mulch basins are trenches dug around the root system of a plant that are filled with coarse woodchip mulch. They are the outlet terminals for the greywater and the mechanism by which the greywater is absorbed and infiltrated to the root system of plants. Greywater is piped underground, is released into the mulch basins, and soaks laterally through the basins to the roots via capillary action.

The size of the basin varies depending on the size and water needs of the plants, the soil type, the number of basins, and the quantity of water needed to be distributed across the whole system. Average basins are 1 ft. (300 mm) deep x 1 ft. (300 mm) wide x 3 ft. (900 mm) long. Some basins may entirely encircle a plant or irrigate multiple plants. They can be half-circles, kidney shaped, rectangular, or essentially any shape depending on needs and the landscape design.

Soil Absorption and Distribution Area

Understanding the infiltration capacity of the soils in the proposed area is critical for designing a greywater system and sizing your landscape distribution area. The distribution area must be sized to allow the graywater to soak into the soil without pooling or runoff.

If the system requires a permit, the AHJ must be provided with the results of a laboratory soil analysis to confirm soil type. A “soil ribbon test”, as described below, is a simple test that can help to unofficially determine soil type if a permit isn’t required.

After the soil type(s) have been identified via laboratory analysis (required for permitted systems) and/or a ribbon test, a simple drainage test, called a “percolation test”, can also be conducted to find out how well water drains on the property. This drainage test will help ensure that good locations for greywater outlets have been chosen.

Soil ribbon test

The soil ribbon test is a fast way to remotely assess soil type in the field. By knowing the ribbon length and texture, it can be approximated if the soil is clay, sandy, or loamy, and how it will drain and hold nutrients. This test only requires some soil, water, and a tape measure to perform. Here are the steps:

1. Gather a soil sample. Collect a sample of the soil by taking a handful of soil from the top 4-6 inches.
2. Wet the soil. Spray a small amount of water onto the soil. Start trying to form the soil into a ball. Keep adding water until you are able to do so.
   *Note – if it is not possible to form a ball, then it is likely that you just have sand for soil.
3. Knead the soil sample. Work the ball in your hands, similar to kneading dough. Remove any bits of organic matter (leaves, stems) and any small pebbles. Keep working the ball of soil until no dirt sticks to your hand. It should feel similar to “silly putty” or “play dough”.
4. Make a ribbon. Start to form the ball into a ribbon by squeezing it in your hand like you would hold a tool handle. Press your thumb so that a ribbon begins to form, extending out over your index finger. As the ribbon grows, move the mass of soil up in your hand, and press your thumb to continue forming a ribbon. Keep doing this until the ribbon breaks.
   

   

5. Measure the ribbon length and record the length.
   *Note: Soil specialists often will make several ribbons in a sample area. This way they can ensure that there is no random pebble or piece of wood that causes a ribbon to break prematurely.

   

6. Check the texture and feel of the soil. Take a small piece of the ribbon, about the size of a pea and place it in the palm of your hand. Add a significant amount of water to the soil so that it becomes fully saturated or over-wet.
7. Rub your index finger on the soil sample. Press your finger on your palm and rub in a circular motion so that you can really feel the soil texture.
   

   

   At this point, you want to classify how the soil feels into 3 categories:

   • Gritty – A gritty texture has the sensation of rubbing dried sugar or sand between your fingers.
   • Smooth – A smooth texture feels like rubbing flour between your fingers
   • Neither – If neither gritty nor smooth texture dominates
8. Determine the soil type by comparing it to the matrix key below. By using the rows as classified by ribbon length, and the columns classified by texture, the soil type can be approximated.
   

   Ribbon Length	Gritty	Smooth	Neither
   0	Sand	Sand	Sand
   0-1″	Sandy Clay Loam	Silt Loam	Loam
   1-2″	Sandy Clay Loam	Silt Clay Loam	Clay Loam
   +2″	Sandy Clay Loam	Silt Clay Loam	Clay Loam

   A soil ribbon that is less than 1″ in length is typically sandy or silt loam with minimal clay content. A ribbon that is between 1-2 inches long is loam. A ribbon that is longer than 2″ long has a heavier clay content. If you cannot form a ribbon, or a ribbon is less than 1″, it is sandy loam.

Laboratory test

If the system requires a permit, the AHJ must be provided with the results of a soil analysis. This requirement can be fulfilled by submitting a soil sample to a laboratory for a soil texture analysis or by providing an existing soil analysis to the AHJ. The soil sample must be taken from the area to be irrigated with greywater. If there is more than one type of soil, representative samples from different areas must be taken. An example of an existing soil analysis is a geotechnical study done for your property. Note that the geotechnical report must be signed and stamped by a licensed engineer or geologist.

Drainage (percolation) test

Identifying soil type (either by ribbon test or laboratory analysis) does not always provide enough information about how well water will infiltrate in a particular location, as deeper soils could differ from surface soils. To ensure that water drains properly in the locations chosen to be irrigated with greywater, a percolation test should be conducted, as described below.

1. Dig a hole, approximately 1 foot deep, in the area where mulch basins are proposed. Insert a ruler or stick marked at inch increments into the hole
2. Fill the hole with water and let it soak in. Repeat this several times so that the surrounding soil is saturated when the reading is taken.
   

   

3. Fill the hole with water again, and this time record how long it takes for the water level to go down a few inches. If it drains approximately 1 inch per hour or faster, the drainage is adequate for irrigating the area with greywater.
4. If it takes longer than two hours for the water level to go down 1 inch, or the hole doesn’t drain all day, don’t use greywater to irrigate this area. Try another location to see if the drainage is better. If you irrigate an area that does not have adequate drainage, you could have pooling and runoff. Plants could also be damaged by water-logged soil, so make sure to irrigate only properly draining soils, or amend your soil by adding compost to improve drainage.

Greywater Guidelines and System Components

Greywater is a unique source of water and must be handled differently from potable water and rainwater. Greywater can be used untreated, or it can be treated to varying degrees to reduce nutrients and disease-causing microorganisms. The appropriate uses of grey water depend on both the source of greywater and the level of treatment desired.

These are some basic guidelines for residential greywater systems.

• do not store greywater more than 24 hours. If stored, the nutrients in it start to break down and create bad odours
• minimize contact with greywater, as it can contain pathogens. All systems must be designed so that greywater soaks into the ground and is not accessible to contact by people or animals.
• infiltrate greywater into the ground; do not allow it to pool or run off. As previously mentioned, soil tests should be performed to assess how fast water soaks into the soil to properly design a system. Pooling greywater is a perfect breeding habitat for mosquitoes, as well as being offensive and possibly a contravention of codes and bylaws
• keep the system as simple as possible. Simple systems last longer, require less maintenance, use less energy, and cost less. Keep in mind that systems with pumps and filters require more commitment and regular maintenance
• install a diverter valve at a convenient location to allow for easy switching between the greywater system and the sewer system
• match the amount of greywater directed to plants with their irrigation needs. Be aware that some laundry products are harmful to plants so do some research to determine any potential problems

System configurations vary significantly in their complexity and size from small systems with very simple treatment to large systems with complex treatment processes. However, most have common features such as:

• A tank for storing the treated water
• A pump
• A distribution system for transporting the treated water to where it is needed, and
• Some form of treatment.

All systems that store greywater must incorporate some level of treatment, as untreated greywater deteriorates rapidly in storage. This rapid deterioration occurs because greywater is often warm and rich in organic matter such as skin particles, hair, soap, and detergents. This warm, nutrient-rich water provides ideal conditions for bacteria to multiply, resulting in odour problems and poor water quality. Greywater may also contain harmful bacteria, which could present a health risk without adequate water treatment or with inappropriate use. The risk of inappropriate use is higher where children have access to the water.

The main components of a greywater reuse system are:

• greywater source(s): washing machine, shower, bathtub, and bathroom basin
• collection plumbing: pipes that transport greywater inside the house to a storage area (for irrigation) or to a treatment system (for treatment and use for flushing)
• surge/storage tank, filter, and pump: optional elements that add complexity and cost but allow greywater to be used for other than irrigation if desired
• make-up water: in times of reduced greywater availability, the greywater stored may be supplemented by potable water for irrigation or flushing. The potable water line must be protected from cross-connection for both in-house consumption issues and off-premises backflow contamination risks
• distribution plumbing: pipes that transport greywater from the system to receiving locations (toilets or irrigation system). This part of the system must be constructed of purple pipe if pressurized, and all outlets labeled to reduce risk of accidental consumption
• toilets and urinals: if used, should be standard or low-flush versions of the typical CSA B45 certified products
• receiving landscape: soil, roots, plants, and mulch basins that use, contain, cover, and purify the greywater

System Types

Greywater systems can be grouped according to the type of treatment they use. There are commercially available systems mentioned in this guide and are for illustration only as we are not recommending any particular manufacturer or system.

Laundry-to-landscape systems

Laundry-to-landscape systems are simple, low-tech greywater irrigation systems that use the washing machine’s internal discharge pump to distribute water through underground piping in the yard. They have no filters, storage tanks or external pumps and can be legally installed anywhere in most jurisdictions without permits or inspections. This type of system is easy to adjust flow levels to different irrigation basins, and easy to modify to accommodate new landscaping. It can be used on flat lots and in homes with no access to plumbing, such as slab-on-grade houses if the washer is near an exterior wall. It is generally trouble-free and easy to maintain, with once-a-year maintenance recommended.

A diverter valve, either manual or automatic, is installed behind the washing machine, allowing greywater flow to be directed to either the landscape (normal use) or to the sewer (for bleach or harsh detergents). The clothes washer’s pump provides positive pressure which can be used to push water fairly long distances horizontally or even slightly uphill. It also simplifies irrigation lines, allowing for a single main line supplying multiple irrigation branch lines. Each branch runs to an emitter in a mulch basin, which is a hole or trench filled with wood chips or a sheathed drip line, also covered in mulch.

Below are general guidelines to help select appropriate locations to irrigate using a laundry-to-landscape system. It is the owner’s responsibility to determine what is safe and appropriate for a particular situation. If the existing washing machine is not operating properly or draining well, it is probably not a good idea to install a laundry greywater system. When in doubt, contact a pump specialist, the washer’s manufacturer, or a greywater professional.

• Sloped yards: don’t distribute water uphill. The washing machine has an internal pump, but it is designed more for volume output rather than pressure. If the yard slopes downhill from the location of the washing machine, the greywater distribution piping can extend as far as needed. On steep slopes, the tubing should be installed in a serpentine pattern to slow down the water. Otherwise, it will rush to the bottom of the hill, and will likely not sufficiently irrigate the upper plants.
• Flat yards: for most machines, it is generally safe to distribute greywater up to 50 feet across a flat yard. Greater distances could result in damage to the washing machine pump since friction losses increase with distance and add resistance to the machine’s pump.

Gravity, branched drain system

This system harnesses the power of gravity to irrigate areas downhill from the home. Its simplicity makes it easy to maintain, but also less flexible. This greywater system expands on the idea of the single fixture system but uses a branched drainpipe network to distribute the greywater to multiple landscape areas. The greywater is still distributed by gravity so the main issue with this type of system is ensuring an even distribution of the greywater to all of the landscape areas desired. The main benefit of this system is the low capital cost, but the main disadvantage is that the distribution pipes can become clogged over time.

System overview

The branched drain system is the ultimate in simple, low- tech greywater systems, designed for decades of trouble-free irrigation. There are no filters to clean or change, no storage tanks, no pumps, and no controllers to program. The system relies on natural processes: gravity, capillary action, and microbes in the soil to distribute and process greywater in the landscape. The only control is a single on-off switch that operates a motorized 3-way valve, as seen below.

In this system, drain lines from greywater fixtures in the house (bathtubs, showers, bathroom basins, and washing machines) are reconfigured to drain to an electrically operated diverter valve, which can direct greywater to either the sewer or the greywater system. This feature allows the user to “turn off” the greywater system if needed, for example if doing a load of laundry with bleach, and instead direct it to the sewer system.

Irrigation installation

Irrigation is through a branched network of flow-splitters and underground emitters that divide and subdivide the flow, spreading it out in the landscape. Emitters are subsurface, each set in a protective valve box enclosure within a mulch basin. The wood chips are an organic greywater filter, catching laundry lint and soap and breaking down impurities through natural microbial action.

Maintenance

Maintenance is minimal as there are no filters, pumps, or storage tanks to clean or replace. Wood-chip mulch beds are a vital component of the system and should be replenished every few years as they subside and turn into rich, healthy soil.

Pumped greywater system

A pumped greywater reuse system collects greywater by gravity from the various fixtures in the house, and in turn pumps it to the desired landscape areas. The main advantage of this type of system is that the greywater can be distributed over a larger area, even at points uphill from the house. The main disadvantage is the higher capital cost.

Greywater from indoor sources drains to a pump basin, which sends it out to the landscape. There are no filters or storage tanks, so maintenance is minimal.  However, a filter may be installed in the system to intercept any debris that could clog the distribution pipes.

Features of these systems are:

• they can irrigate anywhere on the lot, even uphill
• subsurface emitter outlets are placed at mulch infiltration basins
• typically, 16-20 emitters per zone, with either one or two zones
• they can irrigate an entire landscape with greywater
• best for fruit trees, shade trees, and larger ornamentals
• easy to reconfigure if landscaping changes

System overview

The greywater pumped system is a low-tech, high-functioning greywater system designed for years of trouble-free, low maintenance irrigation with gently used water that would otherwise go down the drain and be wasted. It is low-tech in the sense that there are no filters to clean or change, no storage tanks, and no electronic controllers to program. The only control is a single on-off switch which is connected to a motorized 3-way valve.

Like the branched drain system, drain lines from greywater fixtures in the house (bathtubs, showers, bathroom basins and washing machines) are reconfigured to drain to a diverter valve, which can send water to either the sewer or the greywater system.

Unlike the branched drain system, the pumped greywater system includes a pump basin that contains a submersible greywater pump. As water enters the basin it automatically turns the pump on, sending water out to the irrigation piping. The pump basin has a safety overflow connected to the sewer line and protected by a backwater valve.

Underground pump basins

The heart of this system is a pump that sends greywater directly out to mulch- basin emitter outlets in the landscape. The pump allows the system to spread greywater out efficiently and to irrigate uphill from the house if needed. The pump basin should be located outdoors if possible due to the expected odours from the collected greywater.

A common configuration is to put a submersible pump in an underground basin. The basin isn’t considered a storage tank for greywater but rather a housing for the pump. At around half-full it activates a float switch which turns on the pump, sending greywater out to irrigation emitters in the yard. The pump basin also has a safety overflow – if the power is out, for example, greywater will fill the basin and simply overflow to the sewer or septic system until power is restored and the pump activates.

Irrigation installation

Irrigation distribution is through a network of subsurface ball valves, each set in a protective enclosure within a mulch basin. The wood chips are an organic greywater filter, catching laundry lint and soap and breaking down impurities through natural microbial action. An alternate mode of irrigation often incorporated is via sheathed drip lines, which are also covered with mulch.

Maintenance

Maintenance is minimal as these systems are designed for easy access and visibility. There are no filters to clean. The pumps are specifically designed for greywater and have an expected lifespan of many years. Wood-chip mulch is a living part of the system; mulch beds should be replenished every few years as they subside and turn into rich soil.

An anti-siphon valve, often known as an air admittance valve or “cheater vent”, should be installed to prevent any siphoning of the washing machine when using a laundry-to-landscape, gravity branch or pumped branch system.

Manufactured Systems

The intent of the systems described up to this point have been solely concerned with reusing greywater to supply subsurface irrigation needs, as this is one of the two permitted uses for greywater. The other allowable use is for toilet and urinal flushing, which would require that greywater be stored and treated before being pumped to the fixtures. As previously mentioned, any storage of greywater creates odour and bacterial growth issues. This creates scenarios that require more costs and associated treatment and maintenance which will pose problems for homeowners. Reduced or ignored maintenance will undoubtedly result in issues that threaten the safety of the home’s inhabitants as well as that of the users of a public potable water system. Onsite-constructed systems that are intended for toilet flushing may end up being bulky, ineffective, and hard to manage, and so there is a need for manufactured systems that take the engineering and oversight out of the hands of persons that might be ill-equipped to construct a safe system.

In order to treat greywater to a high standard compatible with toilet flushing requirements and any type of irrigation system, manufactured systems utilize various forms of treatment, from filtration to UV sterilization. These systems are tailor-made for each project and connect via an air gap to the municipal water supply in case of a shortfall of greywater, for example if the house were vacant. Multi-stage purification processes make greywater from these advanced systems safe for any type of irrigation, from drip lines to conventional sprinklers.

Generally, these units are a self-contained module that treats greywater to reuse standards before pump or gravity discharge.

Unit features and cost vary with manufacturer and technology used. For instance, some manufacturers have the greywater flow by gravity through the contact chamber and around a UV lamp, where it is disinfected. The UV unit uses no chemicals and has no moving parts and meets or exceeds the performance of other residential UV disinfection systems. Other systems require periodic refilling of chlorine reservoirs that can be done by homeowners. Manufactured greywater treatment systems are also quiet, low-odour, and low-profile so they can blend right into the landscaping or be housed in small areas of a basement.

Sand filter to drip irrigation systems

Manufactured systems are examples of high-tech filtration and treatment. Sand filters are examples of low-tech filtration using natural treatment methods. In low-tech greywater filters, the wastewater flows through a filter medium – sand or gravel. The main treatment process encompasses the retention of particles by the filter material (filtration), and processes that occur due to biological activity in the biofilm on the sand or gravel (treatment). After passing the filter media, the treated greywater can be used for irrigation if desired or may be discharged to a safe location such as surface waters (with permits). If disposal rather than irrigation is the intended end use, it can be infiltrated into the soil if the groundwater level (water table) is deep enough below it

There are generally two different types of greywater sand filters: (a) vertical flow system and (b) horizontal flow system. The selection of the type of filter system depends on several criteria such as ground water level and the elevation at which the greywater pipe leaves the house. The different schemes are described below.

• Vertical greywater filter – The simplest greywater filter is a vertical sand filter where the wastewater is distributed to a basin filled with sand and gravel. There are basic differences of vertical filter design depending on how the effluent is dealt with. The treated effluent can be infiltrated to the soil, or, if permitted, it can be discharged to surface water. At a high groundwater level (< 1m below ground level), it is recommended to construct the filter above the ground and discharge the treated water to surface water, such as a lake, river, or channel. If the groundwater level is lower than 1m below ground, the outflow water can be infiltrated into the soil. In case the treated greywater is meant to be used for irrigation, a storage tank is installed from which the water can be taken, or an irrigation channel can be connected.
• Horizontal greywater filter- The function of the horizontal greywater filter design is in principle the same as in the vertical sand filter, but gravel is used as filter material. In this case the water is not flowing vertically through the filter but horizontally across vertical gravel and stone layers. In contrast to the vertical filter, the horizontal filter is filled with water up to the outlet. The horizontal flow allows a flat construction but requires more horizontal space between inlet and outlet compared to the vertical greywater filter. The basin can be built in the soil providing the outflow pipe ends up above the ground. The height difference required between inflow pipe and outflow pipe of the filter is minimum 5 cm. Within this construction, even pipes from greywater sources that are low above the ground, can be handled if the groundwater level allows an excavation.

A significant downside to sand filters is that they are prone to clogging up over time. While a sand filter used in a swimming pool effectively screens particles from the pool water, it can be backwashed whenever the buildup of particles clinging to the sand reduces the flow through the bed to levels that are not acceptable. Greywater sand filters don’t have this same ability. For this reason, oils and fats from kitchen sinks must be kept out of the discharge to sand filters. Because sand filters require much area, planning, construction and permits, their use as a filtration method is severely limited, and manufactured systems are a better filtration and treatment choice for a house on a residential-sized lot.

Summary

While the reuse of greywater is an ecologically noble cause, it must be noted that, on a fiscal scale, greywater reuse will cost a homeowner more than using potable water over a system’s expected 20-year life expectancy and will require more oversight and maintenance if not installed properly and logically (Econnics, 2010). Consequently, and presently, where there is no immediate need nor legislation to recycle water, there is little consumer interest in embarking on any water conservation measure that has no direct monetary advantage. As well, greywater reuse for the flushing of toilets is all but discouraged due to these same reasons. So, until the water supply situation becomes dire, the need for reusing water in most areas of Canada will remain low, and any greywater reuse will be the result of ecological awareness and responsibility.

Now complete Self-Test 9 and check your answers.

Self-Test 9

Media Attributions

• Figure 1 Mulch basins © Greywater Action. Used with permission.
• Figure 2 Ribbon © Growit Buildit. Used with permission.
• Figure 3 Measure ribbon length © Growit Buildit. Used with permission.
• Figure 4 Using index finger to feel the soil texture © Growit Buildit. Used with permission.
• Figure 5 Timing the percolation rate © Greywater Action. Used with permission.
• Figure 6 Manual 3-way diverter valve © Greywater Action. Used with permission.
• Figure 7 Typical laundry-to-landscape greywater irrigation system © Greywater Action. Used with permission.
• Figure 8 Electric motorized 3-way valve © Valworx. Used with permission.
• Figure 9 Greywater pump basin © Greywater Action. Used with permission.
• Figure 10 Anti-siphon valve © Greywater Action. Used with permission.
• Figure 11 Greyter® residential packaged greywater module – altered from copyrighted image