The laundry to landscape greywater system (LTL) is one of the simplest and least expensive greywater systems that can be installed at a residence. We recommend this type of system for a competent DIYer or landscape professionals with cost conscience clients. Currently this system can legally be installed without a permit in California, Arizona, Texas, New Mexico, and Wyoming if you follow the state guidelines. To view the appropriate guidelines, click on the state.
Laundry to landscape greywater systems use the washing machine pump to distribute the water directly into the landscape without any filtration. In the landscape, the water is pumped through 1” mainline tubing with ½” tubing branches off the 1” mainline. ½” tubing outlets terminate 2” underground in a valve box or over turned 1-gallon potting container located in a mulch basin.
3-Way Diverter Valve:
The Brass 1" 3-way Valve allows the homeowner to send laundry water to the landscape or to the sewer/septic. Laundry water is sent to the landscape during the irrigation season and usually sent to the sewer during the rainy season when irrigation is not required. Divert greywater to the sewer when washing diapers or if any hazardous substances are in the wash. The 3-way diverter valve has arrows on the handle which indicates where the laundry water is being sent. A label must be installed next to the 3-way valve to clearly show how to operate the valve and direct the water.
Auto-vent or Air Admittance Valve:
An Auto-vent or Air Admittance Valve, also called an AAV, Studor valve, or in-line vent, prevents accidental siphoning of water from the washing machine. The auto vent must be installed at the high point of the greywater line for it to function properly. It must be installed in a location that is accessible so it can be replaced. If water ever leaks out of the auto-vent it will need to be replaced.
Blowout Connection or Hose Service Connection:
A temporary blowout connection can be installed to allow the user to blow out the distribution tubing in the event of a clog in any of the outlets. It can also be used during the construction of the system to "tune" or test the system to have even flow from all the outlets. To attach the hose-service connection remove the 1" tubing from the Barbed 1" Adapter (barbed by slip) fitting, which is the transition point between the PVC pipe and the poly tubing. Then insert a Barbed 1" Female Hose Thread Adaptor into the tubing and temporarily connect a garden hose to it. Turn on the hose to send water through the distribution tubing and the outlets can be tested or cleaned with pressurized domestic water. Never install a tee, or other way to leave a hose connected to the system, and always have an Hose Spigot Vacuum Breaker on the hose spigot to prevent any possible cross contamination with the domestic water.
Two irrigation zones can be created by installing an additional 3-way diverter valve in the landscape. Use Barbed 1" Male Pipe End adapters to thread into the valve and connect to 1" tubing. Each irrigation zone must have an open outlet at the end of the 1” tubing to allow the full amount of laundry water an exit point in case of clogging in the smaller outlets.
In the landscape greywater is distributed through 1" high density polyethylene (HDPE). Whenever possible we encourage non-PVC products, since the manufacturing process of PVC is highly toxic and PVC is not recyclable. ABS and HDPE plastics are less toxic and HDPE is recyclable.
If the landscape is flat the 1" tubing run should be should be no longer than 80 ft. to minimize friction and wear and tear on the laundry machine pump. If the landscape slopes downhill, gravity and siphoning will help transport the water and longer runs of 1” tubing can be used. Cut the tubing and insert a Barbed 1" x 1/2" Reducing Tee to send greywater to specific plants. Run the 1" tubing as close to plants as possible to minimize the lengths of ½” tubing required. Long runs of ½” tubing make it hard to obtain even distribution across all the outlets. We don’t recommend running tubing uphill from the laundry machine as this creates back pressure on the pump and can lead to premature wear and failure of the laundry machine pump.
If your site is moderate to extremely sloped downhill, you'll need to run the tubing in S curves, like a switchback trail, to slow the water down and allow for even distribution. If you run the tubing straight downhill, all the water will rush to the downhill outlets and little will come out of uphill outlets.
When installing the tubing, try and keep a flat or slightly downhill slope the entire way. If the tubing travels up and down, it will be harder to get even distribution of greywater.
Dig a shallow trench to lay the tubing and stake it down with garden staple. Bury the system after you have tested it. Alternatively, the tubing can be laid along a fence line or other out of the way place and staked on the surface. Cover it with mulch or plants to protect it from the sun and lengthen the life of the plastic. Remember to maintain the legal setback from the property line for all irrigation outlets.
Greywater is distributed sub-surface using ½” poly pipe into underground emitter boxes or over-turned 1-gallon planting pots. The maximum number of outlets is variable, but 8 generally seems to work best. The more outlets on a zone, the harder it is to equalize the flow out of all outlets without relying excessively on ball valves. We recommend that a 1” outlet be placed at the farthest point of every irrigation zone as a pump preservation measure. If the ½” outlets begin to clog due to user/installation error (i.e excessive use of ball valves), the large diameter 1” outlet will allow all the water to exit the system with out creating back pressure on the pump. If too much water is coming out of the 1” outlet relative to the ½” outlets, add more ½” outlets, raise the elevation of the 1” outlet, or extend the length of the 1” outlet further from the laundry pump.
Ball Valves (Shut-off Valves):
Ball valves are used on ½” tubing outlets to adjust the amount of water that comes out, and may be used for a number of reasons.
- If the irrigated landscape contains a variety of plants with different water needs, a ball valve can be partially closed to limit the amount of water going to a plant relative to the other plants in a zone.
- A plant that requires infrequent watering can have water shut-off entirely while other plants in the zone are still getting water.
- Typically the outlets at the beginning of system will have more water coming out, and may need to be partially restricted with a ball valve.
Potential problems exist when using ball valves
- When partially closing a ball valve, there is a chance that lint can get caught in the valve and create a clog.
- Overuse of ball valves or adding one to the end of the 1" line can restrict the effective pipe size across the entire zone and place back pressure on the laundry machine pump, leading to premature wear.
- Use of other types of ball valves, Green Back Valve Barbed 1/2" have a large internal orifice, while other types have a very small internal orifice and quickly clog.
Mulch basins are used to receive and distribute the greywater to the plant root zone. The mulch basin should be sized so that no ponding of the greywater occurs on the surface of the soil/mulch. Mulch basin size depends greatly on your soil type. Greywater quickly percolates through sandy soils so only a little mulch is required under the valve box. In contrast, greywater percolates slowly through clay soil which may require an 18” wide by 12” deep mulch basin around the valve box to prevent surface ponding of the greywater. Large wood chip mulch is preferred over small wood chips or shredded fiber mulch. Large chips will last longer and require less frequent replacement.
Salt and boron free, liquid laundry detergent must be used when using laundry water to irrigate the landscape. Examples of these detergents include: Oasis laundry detergent, ECOS liquid laundry detergent, and Biopac liquid laundry detergent. Never use chlorine bleach or wash diapers in a greywater system.
- Don’t use mainline distribution tubing less than or greater than 1” in diameter.
- Don’t use long lengths of ½” tubing (more than 2’) or it will be hard to distribute greywater evenly among all the outlets
- Don’t install an irrigation zone uphill from the laundry machine.
- Don’t plug or restrict the 1” tubing at the furthest outlet of a zone
- Don’t use ball valves excessively.
- Don’t allow greywater to pond on the surface of the soil.
- Don’t leave a permanent connection between the domestic water blowout hose and greywater tubing.
For more information on laundry to landscape greywater systems see
|Laundry to Landscape System Diagram||451.76 KB|