A Beginner’s Guide to Gray Water Systems




Some of the water that flows into your sewer or septic system is best swept, far, far away from you and yours. However, a good portion of the waste water flowing through your drains is actually mostly "clean" and free of gross bits and pathogens. This water is often referred to as gray water, or non-potable water.

You shouldn't drink gray water or cook with it, but it comes in handy for other purposes if handled correctly. Learn about the benefits of using gray water. Research the various systems of gray water used with success in your area and with your home’s type of landscape. The following is a beginner's guide to the subject.

What's in the Gray Water?

Most of the excess waste water running out of your drains is composed of runoff from your shower-taking, hand-washing, and clothes-cleaning. This gray water is actually full of nutrients your yard’s plants would love to enjoy as food.

Your local ordinances determine which sources you may use for gray water. Some places only allow water from bathroom sinks, showers, and washing machines. Other ordinances allow kitchen sink and dishwasher waste to be included. There will be more organic matter in waste water from these sources, so using this water is normally forbidden where rules are very strict.

How Gray Water Is Harvested
The simplest way to harvest gray water is to set a deep bucket or pot in the shower and collect your water runoff. The more complicated way is to install diverter valves that send gray water to holding tanks, drain fields, or landscaping irrigation lines.

If you choose the plumbing option, you'll need to have your plumber install three-way valves and backflow valves where the gray water is diverted. The three-way valve allows you to send the water to the sewer lines to avoid frozen or burst garden drainage and irrigation pipes. The backflow valve prevents the waste water from re-entering your water lines.

How Gray Water Is Harvested
The simplest way to harvest gray water is to set a deep bucket or pot in the shower and collect your water runoff. The more complicated way is to install diverter valves that send gray water to holding tanks, drain fields, or landscaping irrigation lines.

If you choose the plumbing option, you'll need to have your plumber install three-way valves and backflow valves where the gray water is diverted. The three-way valve allows you to send the water to the sewer lines to avoid frozen or burst garden drainage and irrigation pipes. The backflow valve prevents the waste water from re-entering your water lines.

Where Gray Water Is Safe to Use
You don't want to use gray water directly on plants that are intended for human consumption, except in the case of very large fruit trees. The gray water is fine for use on ornamentals and under mulch in flower beds and landscape areas.

If you have a boggy area of the yard, you can have excess water drained to that spot. Create a rain garden with willows, cannas, and other plants that favor wet feet. The gray water becomes fertilizer and a source of sweet wetness for this type of garden, and the plants help clean the water so it's safe for wildlife.

It's easier to use gray water in gravity-fed systems if possible. Your plumbing or drainage pro will simply slope drainage pipes downward under the soil away from the gray water discharge point, toward the intended end point. This is an easy way to ensure gray water doesn't end up in the local creeks and streams but instead trickles and filters through your soil.

When to Use Gray Water
Don't let gray water sit in a holding tank, as the bacteria will break down organic bits and cause odors. Filter any gray water that will be stored more than a day or so. If your property does not slope in a way to allow gravity drainage, you can use a pumping system to help move gray water to trees and plants.

When you begin using gray water, switch to laundry, body, and kitchen soaps that are free of ingredients known to be harmful to plants and wildlife. This is the best way to create the safest gray water. Avoid soaps with the following materials listed:
  • Laundry whiteners

  • Borates
  • Ingredients that begin with "sodium"
  • Chlorine bleach
  • Strong degreasers
  • Your local stores should carry a few of the many brands of soap that are safe for gardens and yards using gray water systems.
  • In some locations, gray water systems are becoming mandatory. Even hi-rise owners and multi-family building managers are exploring their graywater options. Each property is unique, so you'll want a drainage and plumbing professional to help you set up your gray water system. Contact C B Lucas Heating & Air Conditioning today to discuss your options for sustainable water usage.