Greywater: A Simple and Effective Resource for Water Starved San Diego

Greywater is water that comes from showers, sinks, and laundry before it combines with toilet water.  Kitchen sink water is blackwater in California.  Many people are nervous about using greywater for fear of contamination and the ick-factor.  Greywater use is not only common but legal and encouraged by public utilities all over Arizona, New Mexico, Australia, and many other parts of the world.  There are over a million users in California alone, and no instance of anyone getting sick from greywater use.

A UCLA report, titled "Graywater: A Potential Source of Water," estimated that if 10% of Southern Californians implemented graywater systems for their laundry, showers, dishwashers and faucets, "the potable water savings would be equivalent to, or larger than, the capacity of a modern, large seawater desalination plant such as those proposed for California."  That’s exciting news for taxpayers!

Last year, San Diego experienced a massive power outage.  Millions of gallons of sewage spilled into the Los Penasquitos Lagoon and the Sweetwater River due to lack of backup power at the sewage treatment plant.  It is clearer than ever that homescale greywater use has its place in our communities.  If each residence around San Diego, and beyond, had laundry and shower greywater systems in place, we could reduced the amount of water being sent from each home to the sewage treatment plant by half. This is a small investment in infrastructure compared to the grand scale of municipal water treatment.

The landscape is designed to capture and treat this slightly used water in the soil, with mulch basins and plants providing high levels of microbial activity which bioremediate any solids or pathogens in the water. This compared to high volumes of water with added solids and pathogens from toilets spilling out directly into our waterways?

Greywater regulations changed in California in 2009 to allow simple Laundry-to-Landscape systems with no permit required, and simple shower systems with specific requirements and a permit.  A simple Laundry greywater system can cost as little as $150 in parts if you do it yourself or as little as $500 if you have a professional install it.  With the potential for producing a couple thousands of gallons of nutrient rich reused water, this is a great investment!  Shower systems can be more complex, especially if you are on a slab, or your bathroom is upstairs.  You may have to hire a plumber well versed in greywater to install your 3-way valve and a landscaper well versed in water conservation, or a water harvesting professional.  The simplest shower greywater systems may cost as little as $600-$800 depending on a multitude of factors including if you have a crawlspace, what kind of slope you have in your yard, how much water is being managed.

A basin designed to collect the water from the
Laundry Machine at the drip line of the tree.
This basin will be filled with mulch.

Many people think of storing greywater and using it in existing irrigation systems, but this is a far more expensive and complex setup than most people need, involving pumps and filters.  A gravity fed system is efficient and cost effective.

Most anyone can implement a Laundry greywater system if their laundry room is on an outside wall, or in an outside building.  By adding a three-way diverter valve to your washing machine hose, you can control whether to send your laundry water out to your yard or down to the sewer.  This is important for instances where you may use bleach or have some other toxic chemicals in your laundry or it has been raining substantially and your yard is saturated, for example.

By keeping the water in a 1” line, you keep pressure from your washing machine pump, allowing you to take the water slightly uphill or over longer sections of garden, and do not constrict the pump flow causing burn out.  From here, you can simply pop a hole in your outside wall and bury your line out to your trees or shrubs.  You can put in as many branches as you need, adding ball valves to control the flow to specific locations. 

It is important to calculate your water budget, which is affected by what kind of machine you have (10-50 gallons) and how many loads a week you do.  Then you can take into account what landscaping you are watering and how much water it will need in an average week.  This way you do not spread the water too thin, or overwater your plants. 

It is also important to use your water on plants that will respond favorably to this slightly more alkaline and saline water supply.  Typically lawn is not ideal since there are potential pathogens in this water and, when a lawn is used for recreation for pets or people, they may come into contact with these pathogens.  You should not water root or leafy green vegetables with this water for the same reason.  Fruit or other trees as well as shrubs are ideal.  Some natives are sensitive to salty soils and may not appreciate this water.  If you are not sure, ask at your local nursery, or contact a water harvesting professional.

Which soap you use matters.  Check out the ingredients and avoid anything with sodium in any form.  Usually powders have a sodium base.  Avoid borax as well.  Two sure bets are ECOS, available at Sprouts and Costco and Oasis, available at Peoples Co-op or online.

There are now more resources in San Diego than ever to create efficient and effective greywater systems.  Look for water harvesting workshops and tours especially with the San Diego Sustainable Living Institute, water harvesting professionals, articles and blogs.  The Olive Branch Green Building Supply has started stocking greywater materials and offering educational resources for greywater.