Your washing machine drains dozens of gallons every cycle. Your showers and bathroom sinks add hundreds more each week. All of it disappears into the sewer, treated as waste – even though most of it is perfectly usable for irrigation. A greywater recycling system captures that water before it leaves your home and redirects it to your landscaping or garden, often cutting outdoor water use by 30–50%.
Installing a greywater system in an existing home is one of the more impactful sustainable upgrades available, and simpler systems are well within the reach of a confident DIYer. The key is starting with the right type of system for your home, understanding your local regulations, and matching the complexity of the install to your actual skill level.
Greywater is the relatively clean wastewater generated by sinks, showers, bathtubs, and washing machines – everything except toilets and kitchen sinks. Toilet waste (blackwater) and kitchen sink water, which contains food particles and grease that support bacterial growth, are excluded from greywater systems for health reasons.
The key property of greywater is that it contains some soaps, personal care products, and low levels of bacteria, but doesn't carry the pathogen load of blackwater. This makes it safe for subsurface irrigation of non-edible plants and, under certain conditions, edible crops (with restrictions on how the water contacts produce). It's not potable and shouldn't be used for drinking, cooking, or any application where it could contact mucous membranes.
Understanding this distinction matters for system design. Greywater should be applied to soil and absorbed – not sprayed where it can mist onto people or edible plant parts, not stored for more than 24 hours, and not allowed to run off your property or pool on the surface. These principles underpin most greywater regulations and should guide how you design your system.
This is the most important step, and skipping it is the most common mistake greywater installers make. Regulations vary dramatically by state, county, and municipality. Some states – California, Arizona, New Mexico, and Texas – have specific, relatively permissive greywater codes. Others restrict or prohibit greywater reuse entirely. Many jurisdictions require permits; some simple systems are permit-exempt.
California's Title 22 greywater regulations are among the most developed in the country and distinguish between simple laundry-to-landscape systems (generally permit-exempt) and more complex mulch basin or drip irrigation systems (permit required). Arizona allows residential greywater reuse under a set of straightforward guidelines without requiring a permit for residential systems under certain flow limits. New Mexico has its own Graywater Act with specific permitted and prohibited uses.
Before purchasing anything or touching a pipe, contact your local building department or health department to ask specifically about residential greywater reuse regulations. Ask whether a permit is required, what uses are allowed, and whether your system design needs to be reviewed. In some jurisdictions, an unpermitted greywater system can result in fines or a requirement to remove the system entirely.
Greywater systems range from simple two-hour installs to complex filtered systems with pumps, storage tanks, and automated irrigation controls. Matching the system to your home's layout, your skill level, and your actual water needs saves money and headaches.
Laundry-to-landscape (L2L) is the simplest and most widely permitted greywater system. It redirects the discharge from your washing machine's drain hose directly to mulch basins or soil around trees and shrubs, using the machine's own pump to move the water. No additional pump is required, no storage tank is needed, and the plumbing change is minimal. This system works best for homes where the laundry is on the first floor with exterior walls accessible to the landscape you want to irrigate. L2L is generally the recommended starting point for most homeowners.
Shower and sink diversion systems capture water from bathroom fixtures and redirect it to sub-surface irrigation. These systems are more complex than L2L because they require gravity-fed drainage lines, often involve cutting into existing drain pipes, and may require a surge tank to handle peak flow from showers. They're better suited for homes with accessible crawl spaces or basements where drain modifications are feasible.
Branched drain systems use gravity and angled distribution pipes to split greywater flow between multiple irrigation zones without any pumping. They require careful planning of pipe slopes and outlet locations, but are low-maintenance once installed because there are no mechanical components to fail. These work well for homes with landscape areas below the level of the fixture drains.
Pumped and filtered systems are the most capable and the most complex. They include surge tanks, filtration, and pumps to distribute water under pressure, enabling drip irrigation and more flexible landscape placement. These systems require professional design in most jurisdictions, carry higher installation costs ($3,000–$8,000 installed by a contractor), and are best suited for homeowners with significant irrigation needs and the budget for a more engineered solution.
For most existing homes, starting with a laundry-to-landscape system makes the most sense. It's low cost, widely permitted, uses no external power, and delivers meaningful water savings without major plumbing work.
Estimated cost: $50–$300 in materials for a basic DIY install
Time: 2–4 hours
Skill level: Beginner to intermediate – basic plumbing comfort required
Permit status: Check locally; often exempt for single-family residential use
What you'll need:
The core materials are a 3-way valve (also called a diverter valve or 3-way ball valve), flexible drain hose or 1.5-inch Schedule 40 PVC pipe, outdoor-rated hose or pipe to reach your landscape zones, and wood chip mulch for the outlet basins. You'll also need basic tools: pipe cutters or a hacksaw, plumber's tape, and a drill if you're routing pipe through the wall.
Step 1: Install the 3-way diverter valve
The diverter valve is the critical component. It allows you to switch the washing machine's drain between the sewer (for when you've used bleach or products you don't want in the garden) and the greywater system. Install it at the standpipe where the washing machine currently drains. Most washing machines discharge through a flexible drain hose that clips or inserts into a standpipe. Remove the drain hose from the standpipe, connect it to the inlet of the 3-way valve, then run one outlet back to the standpipe (sewer connection) and one outlet toward your landscape routing. Label each valve position clearly.
Step 2: Route the distribution line outdoors
From the valve, run flexible drain hose or PVC pipe toward the exterior of the home. If routing through a wall, use a hole saw to create a penetration at a point where the pipe can exit above grade and be concealed or protected. The pipe needs to slope continuously downward from the valve to the outlet – a minimum of 1/4 inch drop per foot ensures the water moves by gravity without pooling in the line. Once outside, the distribution line runs to your landscape zones.
Step 3: Create mulch basin outlets
At each irrigation zone, the pipe terminates at a mulch basin – a shallow depression (6–12 inches deep, 18–24 inches wide) filled with 4–6 inches of wood chip mulch. The pipe outlet should be buried just below the mulch surface, not above grade. The mulch filters and distributes the water, prevents pooling, and reduces odor. Create one basin per outlet; a branched system can serve multiple zones from a single supply line using Y-fittings and equal pipe runs to each basin.
Step 4: Test and adjust
Run a load of laundry with the valve set to the greywater position. Check that water flows smoothly through the distribution line, drains at the expected rate from the outlets, and doesn't pool or back up anywhere in the line. Check the mulch basins for surface saturation – if water pools rather than absorbs, the basin is too small or the soil drainage is poor. Adjust basin size or reduce flow frequency accordingly.
Shower-to-landscape systems follow the same principles but involve more significant plumbing work. The basic process:
Locate the shower drain line in the crawl space or basement below the shower. Cut the drain line just downstream of the P-trap (the curved section that holds water to block sewer gases) and install a diverter valve or a threaded cleanout fitting with a cap that can be redirected. Run a new drain line from this diverter to your distribution system, maintaining continuous downward slope. The flow from a standard shower (2–2.5 gallons per minute) requires a 2-inch drain line at minimum to avoid overflow during use.
Because shower systems involve cutting into your home's drain waste vent (DWV) system, this work is more likely to require a permit and inspection in most jurisdictions. If you're not confident in your ability to work on existing drain lines while maintaining proper venting, this is a reasonable point to bring in a licensed plumber for the drain modification while handling the landscape distribution yourself.
Use greywater-compatible products throughout the household. Conventional laundry detergents often contain salt (sodium), which accumulates in soil and damages plant health over time. Sodium-free or low-sodium detergents labeled as greywater-compatible – brands like Oasis, Country Save, and Ecos – are formulated to be safe for soil and plants. Avoid chlorine bleach loads in the greywater line entirely; divert those to the sewer.
Rotate irrigation zones seasonally. Applying greywater to the same area continuously can lead to soil saturation, salt buildup, or surface ponding. Rotating between zones and replenishing mulch annually keeps the system performing well.
Keep records. If your system required a permit, keep the permit, inspection records, and a basic description of the system on file. This documentation is useful for resale and for any future inspections or modifications.
Installing without checking local regulations is the most common and most consequential mistake. Even in states with permissive greywater laws, specific local rules may override state guidance.
Using PVC pipe rated for pressure rather than drain applications leads to slope problems. Drainage PVC (schedule 40 for drain use) and pressure-rated PVC look similar but serve different purposes. Use schedule 40 drainage pipe and fittings throughout.
Running greywater to edible garden beds without understanding the restrictions. Most greywater codes allow application to fruit trees and shrubs but restrict direct application to edible crops that contact soil. Root vegetables and low-growing edibles where the produce contacts the ground are typically excluded. Check your jurisdiction's specific guidance on food production uses.
Storing greywater for future use. Greywater should be applied within 24 hours of generation. Stored greywater develops odors, grows bacteria, and becomes a health concern quickly. Systems that include storage tanks need careful design to prevent this, typically with UV treatment or other disinfection – and those systems are significantly more regulated than simple direct-application systems.
A basic laundry-to-landscape DIY system costs $50–$300 in materials and saves 15–40 gallons of potable water per laundry load. For a household doing 6–8 loads per week, that's 90–320 gallons weekly redirected from potable supply to landscape use. In areas with water rates of $5–$10 per thousand gallons (and higher in drought-affected regions), annual savings are modest in dollar terms – typically $50–$200 per year – but the value is amplified in areas under water restrictions, in drought years, and in regions where water costs are rising.
The environmental ROI – reducing municipal water demand and the energy required to treat and distribute potable water – is more significant than the direct cost savings for most homeowners. For homes in water-stressed regions or those aiming for sustainability certifications, a well-designed greywater system contributes meaningfully to overall resource efficiency.
Is greywater safe to use on vegetable gardens? It depends on the crop and your local regulations. Most greywater guidelines allow use on fruit trees and ornamental plants but restrict direct soil application to edible crops, particularly those where the edible part contacts the ground. Above-ground edibles like tomatoes or peppers may be permitted with subsurface drip application in some jurisdictions. Always check your local rules and avoid applying greywater to crops you'll eat raw without washing.
Do I need a permit for a greywater system? In many jurisdictions, simple laundry-to-landscape systems are permit-exempt. Shower, bathtub, and sink diversion systems typically require permits in most areas. The only reliable answer is to contact your local building or health department – regulations vary too much to generalize.
Can I use greywater indoors, like for toilet flushing? Yes, but this requires a more complex treatment and storage system than outdoor irrigation setups, and is regulated separately in most jurisdictions. Indoor greywater reuse for toilet flushing typically requires filtration, disinfection, and code-compliant dual plumbing – it's a significant project better suited for new construction than existing home retrofit.
What happens when it rains – does the system still run? Yes, unless you manually divert to the sewer. In periods of heavy rain when soil is already saturated, it's good practice to switch your diverter valve to the sewer position to avoid waterlogging your landscape basins. Most experienced greywater users develop a habit of checking the valve setting seasonally and during wet weather.
How long does a greywater system last? A simple L2L system with quality valves and PVC pipe can last 15–25 years with minimal maintenance. The main maintenance tasks are replenishing mulch in the outlet basins annually, cleaning the diverter valve periodically, and inspecting pipe connections for leaks after significant ground movement or seasonal temperature swings.
California State Water Resources Control Board – Graywater Program: https://www.waterboards.ca.gov/water_issues/programs/graywater/
Greywater Action – How to Build a Laundry to Landscape Greywater System: https://greywateraction.org/greywater-irrigation/laundry-to-landscape/
EPA – Water Conservation: Graywater Reuse: https://www.epa.gov/watersense/showerheads
Arizona Department of Environmental Quality – Graywater Reuse: https://azdeq.gov/graywater
UC Cooperative Extension – Greywater Guidelines for Home Gardeners: https://ucanr.edu/sites/UrbanHort/Water_Use_in_the_Landscape/Greywater/
