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Grey Water And Soil

Grey water is touted as the “new” source of water for landscapes everywhere. But is it really? Like overblown promises, there are some caveats to this statement. And again, soil is being ignored and abused if grey water is used without thought to the household cleaners in them, which REALLY damage the soil.

Grey water has garnered attention as drought continues in South-West USA and Australia. Typically, 50 to 80 per cent of household waste water is grey water from dishwashers, bathroom sinks, tubs and showers. Since the average American family of four uses 400 gallons/day (1,500 litres/day), it’s huge reservoir of untapped water. I’m sure many a water conservationist salivates at the thought.

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As much as recycling water excites me, I’m also leery about the soil damage grey water can cause if used improperly. Imagine all our beautiful soil becoming water resistant, alkaline, saline and reduced soil biological activity. Soil is literally the last thing people think about in their rush to find more water. A couple years ago, I learned about research investigating plants that can withstand the poor soil conditions created by grey water use. I was horrified. Are we willing to sacrifice soil in our desperation for more water? Soil sustains life on earth.

“If you like to eat fine food and wear stylish cloths, then understand that the soil is the source of your food and clothing. Wool may come from sheep and milk from cows, but both of them rely on plants that grow in the soil for their sustenance. Because soil is so common, we often tend to take it for granted – to forget that life as we know it could not exist without soil.” Soil & Crop Sciences Texas A&M University Website

So can we go about recycling grey water responsibly?

Check if you State or Province allows you to use grey water.

Grey water isn’t legal in all parts of the States. Even if it’s legal, codes differ from State to State & even city to city. The State of California allows grey water recycling, as well as many of the arid western States, including Texas & Arizona. States that don’t allow grey water reuse include CT, KY, MD, MI, MN, NE, NH, NJ, NY and WV. The States of Hawaii, Idaho, Maine and Nevada allow grey water recycling for residential irrigation only.

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Health Canada & the National Plumbing Code (CSA B128) say reclaimed grey water may be used for toilets & subsurface irrigation. Canada supports the use of grey water but city codes & regulations may vary. A problem!

Unsuitable climate

Very wet or very cold climates don’t jive with grey water systems. In very wet climates, greywater irrigation is a waste of time, money and effort. In very cold climates (aka probably most of Canada) freezing will prevent you from using the grey water system for part of the year. Using grey water for toilet flushing rather than using in the landscape makes sense, though.

If you’re using grey water for the landscape, check the following soil factors.

Insufficient space

Grey Water And Soil 2

If your neighbours are too close or your garden is too small (or non-existent), discharging grey water into the landscape isn’t an option. I’m sure your neighbours will thank you.

Greywater Reuse website had some interesting facts about land required for landscape discharge of grey water. A 2-bedroom (or less) house requires 28 square meters (301 square feet), a 3-bedroom house requires 38 square meters (409 square feet).

Unsuitable soil

Soil that is either extremely permeable (sandy soil) or impermeable (compacted clay or hardpan) is usually unsuitable soil to discharge grey water into. With the sandy soil, grey water might end up in the neighbours’ yards and/or contaminates the groundwater. Impermeable clay soil is the other extreme, which leads to standing smelly water. Again, be kind to your neighbours. They know where you live.

High water table

Discharging grey water into the soil will only contaminate groundwater.

You don’t have any of those problems. Hooray! Let the grey water system begin. Not so fast. Here’s a few more things you will have to consider.

Sources of grey water

Grey water does not include water from toilets. Water from toilets is termed blackwater and goes into the sewer or septic systems.  However, not all sources of grey water are equal.

Showers are an excellent source of grey water. Remember to use filters to remove hair (snarls pumps). Use liquid soap to reduce sodium.

Grey water from laundry is easily improved by using biocompatible cleaners i.e. Oasis and Bio-Pac.

Water from the kitchen sink is usually OK, except in delicate systems. Grease clogs up the works.

Water from dishwasher, definitely not. Conventional dishwasher detergents are alkaline and contain high amounts of salt. Alternative dishwasher cleaners don’t clean well.

Products for “clean” grey water

Many plants benefit from extra bits found in grey water. Most stuff in household grey water – lint, dead skin, sweat, hair, food, dirt etc – biodegrade into plant nutrients. Household cleaners are the main exception. Flushing mainstream cleaners down the greywater irrigation landscape lines can lead to real ecological problems in soil and aquatic ecosystems.

Using biocompatible laundry detergents is critical to soil health. Grey water friendly cleaners need to be free of any borax, bleach, sodium (found in soaps, detergent and softeners), anti-biotic, and fragrances. Bleach, chlorine and high sodium kills soil organisms and destroys soil structure. Kind of defeats the sustainability goal.

Fortunately there are grey water systems household cleaners available. The Ecology Center recommends these grey water-compatible cleaning products:

  • Oasis laundry liquid
  • Bio Pac Laundry Liquid
  • Biokleen Laundry Liquid
  • LifeTree Laundry Liquid
  • Ecover Laundry Wash (some salt)
  • Mountain Green Laundry Detergent
  • Vaska Herbatergent

Grey water systems costs

The cost of grey water systems depends on how difficult it’s to alter the plumbing, yard size & labour costs/installation.

If you are hiring someone, expect to pay at least $1,000 for a laundry-to-landscape system.

Installing a branched drain system costs $2,000 and $4,000 for a pumped system. Complex systems can be quite a bit more.

High-end residential automated pumped system for drip irritation installation from $5000 – $20, 000.

Of course, you’ll have to factor in yearly maintenance costs as well. The system is expensive. I suspect the prices will start to come down once the technology and techniques become more commonplace.


In my opinion grey water systems are worth it in arid & semi-arid climates, but not so much in very wet or very cold climates. I won’t be putting in a grey water landscape system any time soon where I live. Winters last 5 months!

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