Blackwater is cheaper and easier to process than greywater

In many respects, capturing and diverting greywater is the easy part of greywater reuse; distributing it through your garden can be more complicated and requires careful planning in order to deliver the right amount of water to each area. There are many irrigation alternatives that all have their pros and cons. Some of the commercially available greywater systems offer the installation of the irrigation system as part of the package.

Agi-pipe

One of the simplest ways to deliver greywater below the surface is through perforated pipe (agi-pipe), laid in filled trenches, 100 to 200 mm below the surface. Agi-pipe is flexible polyethylene pipe that has holes in it to allow water to seep out. Common diameters range from 50 mm to 100 mm, so it can easily be laid beneath the surface, even in narrow garden beds. Its flexibility also means it can bend around fairly sharp corners.

Agi-pipe should be laid on a coarse medium, if possible, such as gravel or recycled mulch. The pipe should slope down at a gradient of 1% to 2% (a slope of 10 to 20 mm every metre) to allow even distribution of the greywater.

If small volumes of greywater are being produced then lengths should be between 5 and 10 metres to allow the water to reach the full length of the pipe. If you are producing large volumes of greywater and have an area that requires longer lengths, then one method is to punch large holes every 300 to 500 mm in a large diameter hose (19–25 mm), connect one end of the hose to your greywater source and insert the perforated section of your hose into the full length of the agi-pipe. Depending on the pressure pushing the water, this should allow a more even distribution over a longer length.

Agi-pipe can be permanently connected to your greywater source with fixed piping, or you can leave one end of an agi-pipe protruding out of the ground at various points in the garden to allow a hose to be placed inside. This method allows more flexibility as you can also use rainwater or other water sources to water your garden, when available.

Drip irrigation

Some systems use dripper lines to deliver greywater. The advantage of dripper lines is that they are extremely efficient as they deliver water where it’s needed, at the root zone, and at slow rates that minimise wastage.  This means that larger areas can be irrigated with smaller volumes of water. They are equally suitable for lawns and large areas of individual plants.

However, dripper lines require well-filtered greywater as the perforations in the hoses are very small and can clog easily. The average off-the-shelf dripper system is generally not suitable for greywater as the perforations are too small. However, some companies are producing ‘greywater suitable’ dripper lines, such as the Netafim Bioline range, that have bigger holes and other features that deal with the problem of clogging. However, most dripper lines will still need to be flushed out with clean water periodically.

Mulch basins

Mulch basins are perhaps the only system of greywater irrigation that can deal with no filtration, potentially even from kitchen water (assuming sodium levels are kept to a minimum). It uses large diameter piping that can handle large organic particles and delivers the water directly to the mulch basin.

A mulch basin is simply a scooped out donut-like hole around the trunk of a tree, generally lined at the sides with rocks to stabilise the soil and covered with mulch to avoid people coming into contact with the greywater. The greywater outlet pipe is  situated below the mulch but above the soil. The mulch acts as a sponge that soaks up the greywater and then slowly releases it.

The mulch significantly reduces evaporation, which can also reduce the likelihood of salt build-up and raised pH. Mulch also provides a medium for beneficial organisms to grow. Mulch basins are suitable for large trees, fruit trees and medium-to-large shrubs, and should be sized to accommodate the water surge volume they will receive. For more information see Art Ludwig’s book Create an Oasis with Greywater or www.oasisdesign.net/greywater/createanoasis.

How much water is required?

There are a number of calculations that can help you deliver the right amount of water to a given area.

Given the number of variables, such as soil permeability rates, rainfall patterns, plant needs and topography, it’s hard to look past the simple ‘finger’ method. Stick your finger in the first 20 to 30 mm of the topsoil; if it’s dry you need to water, if it’s wet you don’t. As any gardener knows, the best way to know how much water your garden needs is to spend time in it.

However, it is worth attempting to match your greywater output with your garden’s particular water requirements. This can be done by calculating your soil irrigation rate, the size of the area to be irrigated and seasonal variations, and matching that to your greywater volume, which can be calculated in a number of ways.

A good soil can generally absorb around 20 litres (about two buckets) of water per square metre and, depending on your plants’ needs and climate conditions, should only need watering once a week in summer and once every 20 to 30 days in winter.

As an example, a garden area that is 18 m2 would need 18 (m2) x 20 (litres per square metre), which equals 360 litres. If watering once a week in summer then this area would require around 360 litres per week. A shower with an efficient showerhead uses nine litres per minute. If two people had a shower each day for three minutes that would equal 54 litres per day. Multiply that by seven days and you get 378 litres per week, a fairly close match.

Alternatively, an efficient front-loading washing machine uses around 50 litres per wash (top loaders use around 150 to 200 litres per wash). If you did seven washes per week that would equal around 350 litres, also an approximate match for an 18 m2 garden area.

A useful document that covers many aspects of greywater reuse, including water calculations, is NSW Guidelines for Greywater Reuse in Sewered, Single Household Residential Premises. Although it was written for NSW conditions, it can be adjusted to suit other areas in Australia.

Do’s and don’ts for using greywater

There are some basic commonsense rules that have been developed to minimise the risks associated with greywater reuse. They include:

  • wash your hands after watering with greywater
  • divert greywater to the sewer during wet periods
  • use garden-friendly cleaning products that are biodegradable and low in sodium and phosphorus
  • don’t use greywater that contains disinfectants and bleaches
  • don’t store untreated greywater for more than 24 hours
  • don’t use greywater on vegetables and herbs that are to be eaten raw
  • don’t use greywater sourced from washing nappies or soiled clothes
  • don’t use greywater from the kitchen, unless it has been treated
  • don’t let greywater leave your property
  • don’t use greywater that is still hot as it will kill beneficial organisms in the soil.

Greywater regulations

It is important to understand what is required to install a greywater system on your property. Greywater regulations and permit requirements vary across Australia and you will need to check what the regulations are for your particular area. Permit requirements can even vary from one local council to another within your state or territory, so it is important to contact your local council first. Table 1 in the print version of the Buyers Guide (available here) summarises state and territory regulations and highlights the main relevant documents, but you should also consult your council to check in case of specific regulations for your local council area, or regulation changes.

Conclusion

There is no doubt that greywater is a valuable resource that we should be using, especially with summers becoming hotter and drier across most of the country. It seems crazy to waste our precious drinking water on gardens and lawns when there is a simple alternative readily available. What system or method you decide to use depends on many variables; there is no one system suitable for all applications. Whatever system you choose, you need to ensure that you manage its use correctly so that the real benefits continue to outweigh the potential negative impacts.

How does the use of GREY water differ from water reclamation?

Greywater has been mixed with sewage while water used in water reclamation is derived from cleaning water.

Which of the following is the best example of GREY water?

Correct answer: Waste water that originates from showers, dishwashers, and sinks that can be reused for irrigation. Explanation: Greywater typically includes all household sources of wastewater, with the exception of toilets.

What is Greywater quizlet?

Gray Water. all of the wastewater that drains from washing machines, sinks, dishwashers, tubs or showers that has not touched feces, and can be reused for non-sanitary purposes.

What is GREY black and yellow water?

Within this framework, domestic wastewater may be collected as two (black water/grey water) or three (yellow water/brown water/grey water) component streams. Black water refers to the wastewater coming from toilet bowls while grey water refers to all wastewater excluding the one coming from the toilets.