How to Make the Most of Gray Water to Reduce Your Water Consumption

We’re all used to recycling the cardboard and soda cans that come through our homes, but did you know you can recycle your home’s used water, too? (Don’t worry; we’re not talking about the really dirty stuff!)

As it turns out, used household water can be placed into two categories based on the amount of organic content it contains: sewage (high organic load) and gray water (low organic load). While sewage should always be diverted to your local sewage treatment plant, gray water can be collected and recycled around the home in various ways. 

Separating gray water from household sewage isn’t just a great way to reduce your household’s environmental footprint; it’ll help you save on your monthly water bill. Reportedly, an average person uses around 101 gallons of water every day, much of it coming from the bathtub, washing machine, and shower. Don’t let that lightly used water go to waste! Here’s everything you need to know about recycling gray water in your home. 

What is gray water?

Gray water is defined as gently used household water that comes from bathroom sinks, showers, bathtubs, and washing machines. Wastewater from kitchen sinks, toilets, or any other source that may be contaminated with feces, is not considered gray water.

Gray water is distinguished from household sewage based on the amount of organic content in the water. While organic matter like food, dirt, and biological materials (such as perspiration or hair) are common in gray water in small amounts, the concentrations are so low that the water can be safely repurposed in various ways. Sewage, on the other hand, contains too much organic content to be safely reused at home and should always go to your city’s sewage treatment plant. Used water from toilets and kitchen sinks is considered sewage.

Ways to Recycle Gray Water

There are two main ways to reuse gray water: watering the garden and flushing the toilet. Each use has pros and cons to consider before you make any major changes.

Watering the Garden

Using gray water for irrigation is the most popular way to recycle household water. You can even use gray water for edible plants like fruit trees and vegetables, as long as the water doesn’t come in contact with the edible part of the plant. Gray water contains lots of nutrients that can benefit plants, and it is relatively easy to set up a self-sustaining irrigation system that uses gray water.

A simple storage and filtration system is often all that is needed to divert gray water from sources like the washing machine or shower to outdoor garden beds, especially if the gardens are downhill from these water sources and you can let gravity do its thing. However, if your garden beds are at a higher elevation than your water source, you need to add a pump to your gray water system to move the water efficiently.

Flushing the Toilet

The other main way to repurpose gray water is to use it for flushing a toilet. There’s no need to use perfectly good drinking water to flush the toilet when gray water will do just as well. Using gray water to flush the toilet is a particularly attractive option, since it doesn’t require any filtration beforehand; you can simply pump the gray water directly into the toilet bowl.

Things to Know Before Using Gray Water

You need to consider a few things before you start recycling gray water in your home. First, if you plan to use gray water for your gardens, you must use biodegradable, eco-friendly cleaning products, such as laundry detergent, soap, and shampoo. (This is less of a concern if you only use gray water to flush the toilets.)

Second, before you begin setting up your home for gray water recycling, you should familiarize yourself with your area’s gray water code. What is and isn’t permitted when it comes to recycling gray water varies from state to state, so these guidelines give you a good place to start when it comes to the type of water you can use and how it can be collected. For example, most states prohibit water from kitchen sinks in gray water systems due to its high organic content. However, it is allowed in Washington, Oregon, Arizona, and Montana.

Third, gray water is never potable, and you should avoid coming into contact with untreated gray water directly because it can potentially carry bacteria and viruses. Never use gray water to cook, wash your hands, or bathe.

Lastly, recycling gray water requires minor plumbing work during the initial setup phase. Usually, you don’t need to change your home’s existing plumbing, but pipes must be added and installed throughout your yard and landscape. Be sure to take this into account when planning your gray water recycling project.

How to Collect Gray Water

Gray water collection systems can range from simple to complex, but most experts agree that for residential purposes, the simpler, the better. While gray water collection systems can include pumps and filters, diverting water using gravity and forgoing filters altogether is preferable because pumps and filters are at a greater risk of breaking and requiring ongoing maintenance. Certain scenarios require pumps to divert water when it’s not possible to use gravity, but if you can avoid using a pump, you definitely should. 

Gray water systems that divert water from sources like the shower and laundry machine for use outdoors connect to the source’s main drainage pipes and divert the water into the gardens using an intricate system of PVC pipes buried under the soil. The pipes are installed at a consistent downward slope, with fittings that break up the flow of water into smaller and smaller pipes that are then diverted to specific plants. Two of the most popular and well-known residential systems that work in this way are the Laundry-to-Landscape system and the Branched Drain system, both of which were invented by Art Ludwig. These systems can be time-consuming to set up, but once the installation is complete, they are relatively self-sustaining and can last for many years.