Installing a Grey Water System

Laundry-to-Landscape Grey Water System

It’s not news that Northern California has experienced heavy storms this winter, which have gratefully pulled us out of severe drought. However, we still aim to be water conscious, so we’re sharing some tips on installing a Grey Water System for your laundry machine.

Grey water is water that has been used once. Grey water can be collected from the shower, bath, sink and laundry unit. You do not need a permit to install a greywater system from a clothes washer, per the California Plumbing Code, but you will need to check with your city’s Building Division to see if they require a permit. You should not store grey water. Standing grey water will allow bacteria to grow and will produce a bad odor.


Front Loading Washer: 15-20 gal/per load

Top Loading Washer: 30-50 gal/per load

The average family does 6-7 loads of laundry a week! A family could save up to 18,200 gallons of water a year using a grey water laundry-to-landscape system.

The first step when installing a grey water system is to consider how much water will be collected and how often. You’ll also want to determine where the grey water will be most useful in your backyard. It is best if the irrigation zone is downhill, this way gravity can do the work for you and you can avoid using pumps. Grey water pooling or run off is not allowed, and the distribution of grey water is all sub-surface, in order to prevent contact with humans and pets. The estimated capacity for grey water is ½ gallon per 1 square foot a week.  It’s recommended to use 5-8 emitter outlets within 100’ of the laundry machine.

Trees, including fruit trees, and shrubs are ideal for using grey water. Do not water leafy greens, root veggies or acidic soil loving plants. You should also use a biodegradable laundry soap (recommended brands: Oasis and Biokleen).


  • 1” Brass 3-Way Valve
  • 1” Hose Clamp
  • 1½” Air Admittance Valve
  • 1” PVC Male Adapter (Slip x Male Pipe Threads)
  • 1” Barbed Male Adapter (Male Pipe Threads)
  • 1½” x 1” Reducing Bushing PVC (Slip x Slip)
  • 1½” PVC Female Adapter (Female Pipe Threads x Slip)
  • 1” Barbed Adapter (Barbed x Slip)
  • 1” 90° PVC Elbow
  • 1” PVC Pipe Schedule 40 (length variable by installation site)
  • 1” &  ½” Polyethylene Tubing (length variable by installation site)
  • (5-8) 1”  x ½” Barbed Reducing Tee
  • (5-8) ½” Barbed Ball Valves
  • (5-8) Round Valve Boxes
  • Mulch
  • U-Shaped Stakes for Poly Tubing
  • Channel Lock Pliers or a Pipe Wrench
  • PVC Pipe Cutters
  • Trenching Shovel
  • Teflon tape
  • PVC Cement
  • Metal Hanger or Plastic Strap
  • Screws for Metal Hanger or Plastic Strap
  • Cement bit (for creating holes in stucco)
  • Sikiflex Adhesive Sealant
  • White Spray Paint
  • Biodegradable Laundry Soap (Oasis or Biokleen)

Once you’ve mapped out your grey water irrigation zone we’ll start at the laundry machine with your 3-way valve. This valve will allow you to control whether your grey water goes to the garden or the sewer. You’ll simply turn the valve knob to the proper flow. Clearly label which direction of the valve leads the water to the sewer versus the irrigation zone. You’ll want to send the water to the sewer during the rainy months when the plants don’t need as much irrigation, or when washing diapers or using bleach or any other chemical which could harm your plants. Avoid products that include salt (sodium), boron (borax) or chlorine bleach.

Connect the valve to your washing machine hose using the 1” barbed male adapter and a 1” hose clamp. Then wrap Teflon tape 4-5 times around the threads of two 1” PVC male adapters and secure them tightly to each side of the 3-way valve. Next attach the sewer line to one side of the valve using your PVC cement and attach the grey water side to a few inches of PVC pipe. Use screws and metal hangers or plastic straps to secure the 3-way valve to the wall above the washing machine for easy access. The sewer side is now complete.

Next you’ll use a 1” PVC tee and connect it to the garden side of your valve. Add PVC pipe several inches higher than the 3-way valve and use the 1½” x 1” Reducing Bushing PVC and then the 1½” Female Adapter to attach the 1½” Air Admittance Valve. This is very important piece. The Air Admittance Valve acts as a vacuum to ensure backwater from previous washing cycles does not come back into the washing machine.

Now attach PVC pipe down the wall. Use a cement bit to drill a hole through the stucco wall and now you can add a 1” 90° Elbow to your PVC pipe and work your way out of the house. Use the Sikiflex Adhesive Sealant to seal the hole in the wall. Use another 1” 90° Elbow to drop the PVC piping towards the ground.

Now that you’re outside, dig the irrigation trenches about 6” deep.  Also, dig the 5-8 holes where your emitters will be. Dig the holes deep enough for your round valve boxes.

Once the holes and trenches have been dug, you can bring the PVC piping down to your trench and connect the Polyethylene tubing to your PVC with a 1” Barbed Adapter. To protect exposed PVC from the sun, spray paint the PVC white. In high traffic areas, like walkways, you can protect the polyethylene tubing by placing the tubing in a wider PVC pipe.

Use the barbed 1” x ½” Reducing Tee to split the tubing off to your first outlet.  Insert your ½” Polyethylene tubing in the Reducing Tee. Drill a hole in the Round Valve Box at least 3 inches from the top, and insert the ½” tubing. Connect the ½” Barbed Ball Valve.

Before you cover the trenches in dirt, run a test load in the washer and adjust any tubing as needed. Use U-shaped stakes to secure tubing in your trenches, and cover with dirt. Place mulch around your Valve Boxes and beneath the Ball Valves. This will both protect the valves, hold the water longer and catch any laundry debris like lint.

The maintenance for a Laundry-to-Landscape Grey Water System is minimal. Occasionally check the Ball Valves to be sure they are flowing correctly. Remove any lint or hair from the mulch and replenish mulch as needed.


An Oasis with Greywater by Art Ludwig – A great visual map of the Laundry-to-Landscape Greywater System – Video of a Laundry-to-Landscape Greywater Installation by Berkeley’s Ecology Center