A Guide to Greywater Systems

suspended water droplets - a guide to greywater systems

Water is the most important, and the most wasted, substance we use in our homes. The average American will use 88 gallons per day, according to the EPA, with much of it going straight down the drain without being used for its intended purpose first.

The EPA reminds us that installing low-flow fixtures can save up to 20% of a home’s water consumption. Depending on your home and your locale, however, you might be looking for more intensive water saving strategies. A greywater system could be the solution.

What is Greywater?


Greywater is water that’s been used for a shower or load of laundry, or for washing your face. It’s a little gross, because you’ve just washed yourself or your clothes in it, but it’s not so gross that it can’t be useful.

Water that’s so gross that it can’t be useful (i.e. water that’s been used by toilets) is called black water. Black water is handled by your sewage system or septic tank. Any water that you have washed diapers in falls into this category and should definitely not be used as greywater.

Water from kitchen sinks and dishwashers is, if you’ll pardon the pun, in a grey area. Some regions consider it to be greywater, but most consider it black. The issue is the amount of organic matter that kitchen wastewater contains, which could lead to high levels of harmful bacteria and pathogens building up in a greywater system.

What Greywater Can and Can’t Be Used For


Greywater is perfect for outdoor watering needs like landscaping and gardens. The key is to switch your soaps to something biodegradable and phosphorus-free so the water doesn’t contaminate your soil and harm your plants. Although that’s really a switch you should be making anyway. Ideally, greywater will only contain traces of plant-friendly soaps and detergents that aren’t too saline or alkaline.

Most sources recommend not using greywater directly on edible plants or on indoor plants. Don’t use it for pet water or to surface water your lawn. Greywater could contain harmful microorganisms, so it’s better that it not come into contact with people or animals.

Since greywater can’t sit for more than 24 hours (because it starts to go septic), some people construct mini-wetlands in their yards to handle any extra water and keep it moving out of the system before it can turn to black water.

Indoors, treated greywater can replace fresh water in your washing machine and toilet tanks. Currently, greywater use in showers or bathroom taps isn’t generally recommended, although as treatment options improve, we could see that change.

The Benefits of Greywater Systems


water drop - a guide to greywater systems

Recycling water has the obvious benefit of reducing your water consumption, which reduces your monthly bills and your water footprint. Other specific benefits include:

  • Prolonging the life of your septic system by reducing the water load
  • Not feeling bad about using water during a drought or shortage
  • Providing your plants with a more nutrient-rich water supply
  • Providing yourself with a water supply if your home is off-grid

Tiny houses and off-grid homes and cottages benefit most from greywater systems, particularly in water-stressed regions. They reduce water intake from wells, tanks and cisterns, allow homes to manage wastewater safely and in some cases, lower the risk of actually, actually running out of water.

If you’re in a standard residential home, and already have high-efficiency plumbing and good water-saving habits, you probably wouldn’t see enough of a benefit to justify the cost of installing an extensive system. That could easily change, however, depending on your geographic locale.

Many communities regularly face water shortages at some point in the year. That trend is expected to increase as America’s supply of fresh water diminishes, meaning that intensive water saving strategies like greywater systems will make more sense in more homes as time goes by.

Different Types of Greywater Systems


The main types of systems are distinguished by whether the water is moved through the pipes by gravity or by a pump, and whether the water will be distributed outside or recycled for indoor use, which will require some kind of water treatment.

At its most basic, greywater systems will be composed of plumbing that collects the greywater, a holding or surge tank with an overflow that connects to the sewer or septic system and a distribution system.

The simplest of these diversion types of systems are gravity based. Gravity-based systems are designed to passively allow water from the home to flow through irrigation pipes and reach your lawn or garden. Diverter valves allow you to direct water either to your garden or to the sewer/septic tank, which is a necessity in places that get hard winters.

If your home and yard are set up such that gravity does not help you (i.e., if your property doesn’t have sufficient slope), you can pump the water where it needs to go. Systems that use pumps introduce lots of other complexities to the project. There will be parts to maintain and replace, as well as additional electricity use. These are all factors to consider if you’re trying to save money or use fewer resources.

Greywater systems that recycle water for indoor use are more complicated. If the greywater is going to be used inside, it needs to be treated to remove pathogens and chemicals. These systems typically treat the water through some kind of filtration process and either chemical or UV disinfection.

Installing a Greywater System


The first step to installing a greywater system is familiarizing yourself with municipal codes pertaining to these systems. They’ll differ from region to region, and they frequently change as systems become more common and technology develops. There will be limitations on what you can do (your greywater cannot end up in your neighbour’s yard, for example). And there will undoubtedly be permits to apply for. Installations for new homes is often easier, but it’s common to retrofit older houses, too.

There are companies that specialize in this technology, and they can help you with design and installation. Because of the impact untreated greywater can have on local drinking supplies, some regions will require that all plumbing for this project be completed by a licensed plumber.

With basic plumbing skills, however, you can also DIY a simple greywater system for outdoor irrigation. Art Ludwig offers up instructions for a laundry to landscape system here.

While greywater systems won’t make sense for every home, they’re worth considering if you live in an area where water shortages are frequent or if your irrigation needs outstrip what you want to pay for water. In the right contexts, these systems could be a game changer for you.

Feature image: Gabriel Peter; Image 1: Pixabay

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