How To Install a Graywater Irrigation System

Graywater irrigation systems present an eco-friendly approach to reusing water from laundry for landscape irrigation. These systems can noticeably reduce water consumption and utility bills while keeping your garden vibrant and thriving. The video above features This Old House plumbing and heating expert Richard Trethewey helping a homeowner reroute laundry graywater into her yard. Below, we’ll outline this process and provide more resources for homeowners looking to plan and install their own systems.

Understanding Graywater Systems

According to the Environmental Protection Agency, graywater refers to the relatively clean wastewater originating from bathroom sinks, bathtubs, showers, and washing machines—but not kitchen sinks or dishwashers. Despite being non-potable, this water serves adequately for irrigation purposes.

Benefits of Graywater Irrigation

Graywater irrigation systems redirect this water from the sewer or septic system directly to your landscape, meaning you don’t have to use potable water on your plants. Installing a graywater system comes with multiple advantages, which include the following:

• Alleviates treatment systems: Less water flows to septic systems and municipal treatment plants, reducing their load.
• Reduces utility costs: By diminishing water consumption, homeowners will also lower their water bills.
• Reliable water source: Even during drought conditions, graywater provides a consistent source of water for irrigation.
• Replenishes groundwater: Contributes positively to groundwater supplies by redirecting potentially wasted water.

The size of these benefits may depend on where you live. For example, a homeowner in California, which often experiences water shortages and thus water use restrictions, may see more sizable benefits than homeowners in other parts of the country.

Types of Graywater Systems

Different types of graywater systems cater to varying needs. They include:

• Branched drain system: Utilizes gravity to distribute water across multiple irrigation zones.
• Laundry-to-landscape system: Diverts water from the washing machine directly to the garden.
• Pumped systems: Handles graywater from multiple sources, suited for covering larger areas with more complex setups.

In the video, Trethewey installs a simple, gravity-assisted laundry-to-landscape system. To figure out what system your home needs, you’ll have to do a little planning.

Planning Your Graywater System

Before you start buying pipes, take a look at your municipal or local regulations and plan out the route a potential irrigation system might take.

Check Local Regulations

Graywater systems are subject to diverse regulations that vary by location. Here are some factors to be aware of:

• Irrigation line depth: Lines should be buried to a proper depth to ensure safety and effectiveness.
• Permit requirements: Securing necessary permissions may be part of the installation process.
• Setback requirements: Defining distances from property lines and structures is crucial.
• Source restrictions: Some water sources, such as kitchen sinks, may be prohibited.

Assess Your Landscape

To optimize the system, evaluate your yard and its specific needs. This involves doing the following:

• Checking current utility lines. Call 811 before you dig.
• Determining suitable plants. While graywater is beneficial, don’t use it on edible root crops (e.g., potatoes).
• Ensuring proper drainage. Pooling water can cause problems for your yard and potentially even your home’s foundation
• Mapping irrigation zones: Understand plant water needs and assess yard topography to efficiently create irrigation zones.

Choose Your Water Source

For most homeowners, a washing machine is an ideal graywater source. You can access the plumbing easily and isolate it from the rest of the home’s pipes, and it generates plenty of water during use. Bathrooms also produce graywater, but unless you’re renovating already, you’ll have to cut into walls and run new pipes. Thus, it’s typically easiest to source graywater from laundry.

One advantage seen in the video is that the homeowner’s washing machine was high enough that the system could run on gravity alone. However, this won’t be the case if your laundry is located, for example, in the basement. For that, you’ll need a pump, more complex plumbing, and a permit. We recommend hiring a licensed plumber for this type of installation.

Installing a Laundry-To-Landscape System

A laundry-to-landscape system is among the most straightforward graywater setups to install. In most areas, it doesn’t even require a permit as long as you follow state guidelines. While your home’s layout might have different requirements, here’s an outline of Trethewey’s process.

Tools and Materials

Trethewey was able to use a system conversion kit provided by the city, complete with tools. Contact your local water department or utility company to see if similar kits are available in your area. If they aren’t, here are the basics you’ll need:

• 1-inch high-density polyethylene tubing
• 3-way diverter valve
• Drill/driver
• Irrigation valve boxes or flower pots
• Mulch
• Pliers
• Polyvinyl chloride (PVC) pipe cutter
• PVC pipes and fittings

Step-by-Step Installation Process

This is how Trethewey installed a simple, gravity-fed irrigation system:

1. Mount the 3-way diverter valve behind the washing machine to manage water redirection.
2. Connect the washing machine’s discharge hose to the diverter valve’s bottom port.
3. Route PVC piping from the diverter’s left port to a utility sink to vent unacceptable greywater (e.g., if you used bleach).
4. Drill a 1-inch hole through the exterior wall to guide the irrigation line outside.
5. Lead PVC piping from the diverter valve’s right port through the wall and outside.
6. Install a vacuum breaker on the diverter valve’s T-fitting to stop potential siphoning.
7. Connect the PVC drain line to the 1-inch high-density polyethylene tubing for landscape irrigation.
8. In your yard, lay out irrigation tubing, adding T-fittings for each plant station.
9. Construct mulch basins at each irrigation site to filter graywater and avoid pooling.
10. Place irrigation valve boxes or flower pots over each outlet to deter root intrusion.

Fine-Tuning the System

Once the system is in place, make sure that it’s distributing water evenly. Here are some steps to take:

• Modify tubing positions or mulch basins to improve water flow to plants.
• Inspect for leaks, tightening connections as necessary.
• Monitor plant health and soil moisture over time, tweaking the system as required.

Maintaining Your Graywater System

While a graywater irrigation system can save you money, you’ll need to make a few changes around the house to get the most out of it.

Using Graywater-Friendly Products

Your first priority, once installed, is to switch to products that are safe to pour on your plants and directly into the groundwater. The Sierra Club, like Trethewey, advises soaps and detergents with low sodium and boron content. For laundry detergent, this typically means liquid rather than powder. Look for plant-friendly, biodegradable products. The Ecology Center recommends Oasis, Bio Pac, and Soap Nuts, but there are many brands to choose from.

You can, of course, still use stronger synthetic products when necessary. Just make sure you remember to direct this graywater into your regular drainage system so it can process it as wastewater.

Regular Maintenance Tasks

A laundry-to-landscape system doesn’t filter water for debris such as lint, so you’ll need to inspect the system on a regular basis, particularly when you’re using it frequently. Keep the following do’s and don’ts in mind for system upkeep.

• DO make sure everyone in the household knows how and when to use the system.
• DO regularly check pipes and tubing for clogs or leaks.
• DO reassess your plants’ watering needs seasonally and make adjustments.
• DON’T allow roots to grow into irrigation pipes.
• DON’T drain graywater onto bare ground—replenish mulch basins as necessary.

Maximizing Graywater Efficiency

As you get used to using your system, you can start to make tweaks to get the most out of it:

• Arrange plants with similar watering demands together.
• Apply mulch generously to reduce evaporation and conserve moisture.
• Incorporate rainwater harvesting for a well-rounded water management system.

Our Conclusion

In many climates, installing a graywater irrigation system serves as an effective method of water conservation and environmental preservation. With adequate planning and regular maintenance, you can create your own sustainable landscape watering solution. Though it necessitates an initial investment of effort and resources, the long-term benefits—both financially and environmentally—make it a compelling proposition for many households.