How can homeowners recycle grey water?

Here in California – and in many parts of the world – water scarcity is a way of life. Thankfully, most of the water that we use indoors can be safely reused for outdoor irrigation and toilet flushing. This is called grey water.

Grey water is used water from sinks, showers and washing machines. It makes up the majority of household wastewater. It has small amounts of chemicals from soaps and shampoos, but these are manageable during reuse. Surrounding soils absorb some of these chemicals, and plants can use others for food.

backyard of home with benches, plants, grass, and trees
This yard in California is watered with greywater from showers, laundry, and bathroom sinks. Reuse of water in this safe way helps the homeowners enjoy some shade and green space. Credit: Greywater Corps

Waste from toilets, kitchen sinks and dishwashers is considered black water. Black water needs special processing, usually from a wastewater treatment plant, to be safe.

At Greywater Corps we specialize in grey water systems for irrigation. Most of our projects involve retrofitting single family homes to separate grey water from black water. We then set up systems to reuse that greywater to feed plants outside.

First, we get in the crawlspace under the house and modify the plumbing to separate grey water from black water. From there we install four types of systems, three of which use untreated, raw greywater, meaning no filters and very low maintenance. They are:

Laundry to landscape (L2L): this type of system uses the washing machine’s internal pump to move greywater. It can irrigate across level terrain or downhill.

Branched drain (BD): this system uses gravity flow directly from plumbing fixtures to move gray water. It can only irrigate downhill.

Pumped system (PS): pumped systems use a motorized pump to move greywater. They can irrigate uphill.

photo of crawl space under home with dirt, concrete, pipes, wires, and graphic overlay with text showing what the added greywater plumbing system would look like next to the existing one
Staff from Greywater Corps goes into the crawl space under homes. There, they divert water from sinks, showers and washing machines into the grey water collection system outdoors. Credit: Greywater Corps

Untreated grey water is released in trenches 8 to 12 inches deep, filled with woodchip mulch. These trenches, called mulch basins, allow grey water to percolate laterally through the mulch without ever reaching the surface. Gray water is released inside valve boxes embedded in the mulch and filters out to the landscape from there.

Grey water is not ideally suited for lawns or other water-intensive landscaping, but it can be applied to a wide range of landscape designs and plant palettes, from verdant tropical reveries to riparian habitats shaded by sycamores, to edible gardens bursting with fruit. In low water gardens, grey water can be applied to key plants like fruit trees, shade trees and perennials. Grey water systems generate large amounts of water and discharge it all at once, so they are best paired with larger plants that can absorb it.

ground with soil, plant leaves, mulch, and labeled equipment consisting of tubing, emitter, and shield
After diverting water from sinks, showers and washing machines, the water flows into a yard with tubing and trenches. Mulch is used to hold the water, which can then soak out into the surrounding soil to provide water for plants. Credit: Greywater Corps

We also install advanced systems that use varying levels of treatment to clean grey water for applications such as drip line irrigation. These systems come with greater costs and maintenance, but also allow much greater flexibility and enhanced capabilities.

While most of our projects involve single family homes, we have also built systems at apartment buildings, schools, universities, hotels and more. Every building can find its own strategies to best manage this precious resource we call grey water.

Answered by Josep Ferrer, Greywater Corps

For more information visit our website

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3 thoughts on “How can homeowners recycle grey water?

  1. In thinking about L2L usage, I am concerned about sodium from detergent building up in the soil. Is there any long term analysis you can share?
    (I am a horticulture teacher and appreciate all the great info shared via this blog)

    1. Thank you, Gretchen, for being a reader! We’ll reach out to Josep and see if he has an answer. SVF

      1. Hi Gretchen – this is from Josep “Yes there are two ways around this: use low/no sodium detergents or other cleaners like laundry balls; or use greywater on salt tolerant plants. We have not observed any issues with this. We always recommend switching to greywater friendly detergents when using L2L.” SVF

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