Greywater

What is Greywater?

Greywater diagramGreywater is used water from sinks, showers, baths and washing machines that can be safely used for outdoor irrigation! It is not wastewater from toilets!

By re-using laundry water, residents can conserve water and reduce the energy, chemicals, and costs involved in treating water to drinking water (potable) quality.

The easiest way to utilize greywater is with a Laundry-to-Landscape (L2L) system. Creating a L2L greywater system in your home can play a critical role in drought resilience given its ease in both installation and maintenance. In efforts to reduce potable water use for irrigation purposes, there have been recent changes to the California Plumbing Code regarding gravity-fed greywater that make it easier for residents to create their own L2L system.

Basic Greywater Guidelines

Greywater is different from fresh water and requires different guidelines for it to be used safely:

  • Do not store greywater for more than 24 hours. If you store greywater, the nutrients in it will start to break down, creating bad odors.
  • Minimize contact with greywater. Greywater could contain pathogens so your system should be designed for the water to soak into the ground and not be available for people or animals to drink.
  • Infiltrate greywater into the ground and do not allow it to pool up or run off. Knowing how well water drains into your soil or the soil percolation rate of your soil will help with proper design. Pooling greywater can provide mosquito breeding grounds as well as a place for human contact with greywater.
  • Install a 3-way valve for easy switching between the greywater system and the sewer/septic.
  • Match the amount of greywater your plants will receive with their irrigation needs.