Greywater
What we call “greywater” is any previously-used water that does not contain human waste. It’s the water from your faucets, shower, bath, and laundry that leaves your home. It’s water that can -- and should -- be reused, but it requires a bit of plumbing to make that happen, and some thoughtful care.
A simple irrigation system is the most basic and resourceful way to utilize greywater. But, because it does contain some waste elements -- from food, skin oil, dirt, etc. -- you should not use it to water any edible plants, excluding fruit trees.
Isn’t it all a little gross, though, to be diverting much of the water you typically send through sewer pipes on and around your trees? No, it's actually really tasty (for your plants) and nutritious. Of course, don’t even think about consuming it yourself, as it could cause health problems. Let your trees consume it for you!
If you install a greywater system, make sure to switch your soaps, shampoos, etc. over to ones labeled as biodegradable and plant friendly. More often than not, these labels also mean non-toxic to humans and pets as well, but you’ll want to check.
Note that the soap products you choose should contain little to no chlorine, boron, or salt. Even if some limited amount may technically be “safe” for humans, these may severely damage your soil.
Greywater basics
There are standard guidelines for using greywater. For starters, it should not be stored for more than 24 hours. After that amount of time, the nutrients in the greywater can start to break down causing odor and potential health hazards.
It’s important that your system be constructed in such a way as to allow you at any time to easily divert, say, old grey water and any build-up straight into the sewer system and bypass your irrigation system altogether. It’s essential to retain this option.
You obviously want to minimize human contact with greywater (it cannot be reused for washing clothes or drinking). So, irrigation systems should be set up so as to water the plants from under the ground. Any pooling of grey water can result in unsanitary areas or breeding grounds for bugs.
Before installing a greywater irrigation system, check your local laws. Some systems in some states and municipalities are illegal; in any case, regulations vary greatly. So, check first to see what you can do and specs to follow in terms of how to go about it.
What’s the simplest method of installation? It focuses on diverting nothing more than your laundry water to the landscape. This system, designed by Art Ludwig, merely requires a diverter valve attached to your washing machine. A series of hoses takes the grey water to mulch basins outside.
Your washing machine already has an internal pump to force the water out, and mulch basins help ensure a safer and more effective delivery of the water once it’s outside. These systems can cost anywhere from $75 to $200 to install DIY. Need a pro to help? Professional installment can reach up to $2,000.
Note that for the true engineer, greywater systems can be much more advanced -- they can even filter toilet bowl water and deliver water for edible plants. Many hotels and large apartment complexes already implement highly sophisticated greywater systems in order to maximize efficiency and cut down on costs. A lot is possible. But, think in terms of the above to get yourself going.
Learn more on ways to save water and money with LADWP.
Learn more about the assumptions behind Magenta House water and power savings calculations.
DETAILS
Upgrade: Greywater recycling system
Goal: Use greywater from washing machine to irrigate plants.
Potential Savings*: Potentially quite significant, but too much variability to assign an average.
Skill level: ★★☆
SAVINGS*
For a drip irrigation system greywater systems can cost anywhere from $75 to multiples of thousands depending on what you do and how you do it.
A system that focuses on the laundry alone can save from 25 gallons (horizontal loading) to 40 gallons (vertical loading) per use.
But, because greywater systems vary so much in scope, the water, energy and monetary savings are too variable to be otherwise estimated here.
