Laundry-to-Landscape
Graywater Systems
Start simple.
This low-cost, easy-to-install system redirects graywater from the discharge hose of your washing machine through an irrigation line to specific plants. No permit is required as long as the 12 guidelines set forth in the current graywater code are followed.
Key points
Laundry to Landscape System
Captures graywater from the discharge hose of your washing machine
Diversion upstream of sewer drainpipe
No alteration to existing plumbing
Washing machine pump used to distribute graywater
3-way diverter valve diverts water either to the landscape or the septic/sewer
Vacuum breaker or anti-siphon component on the landscape side of the 3-way valve
Water is slightly pressurized so the system is less demanding of strict grade (fall) than a gravity-only system
Required Parts
(see diagram above) Available from local hardware stores and/or irrigation supply stores.
Indoor parts
A. Brass 1" 3-way valve
B. PVC 1" Male Adapter (S x MPT)
C. Barbed 1" Male Adapter (MPT)
D. PVC 1" 90 Elbow
E. PVC 1" Tee
F. PVC 1.5" x 1" Reducing Bushing (SxS)
G. PVC 1.5" Female Adapter (FPT x Slip)
H. Auto-vent or Air Admittance Valve 1.5”
Outdoor parts
J. Barbed 1" Adapter (BxS)
K. Barbed 1" Tee
L. Barbed 1" x 1/2" Reducing Tee
M. Poly 1/2" Tubing
N. 8 - 7" round valve
O. Green Back Valve Barbed 1/2”
P. Barbed 1" Coupling
Indoor Assembly
See below for descriptions of each component in detail.
3-way diverter valve
Must be mounted above the “flood rim” (top) of the washing machine with the washer discharge hose connected to the middle port. Ensure watertight connections (to avoid water-damage from leaking Graywater) by using proper tightening (se teflon tape (on threads) and glue (on slip connections) to make water-tight connections. Secure into the wall studs using pipe brackets or strapping.
Anti-siphon Assembly
Lets air into the system through a 1-way spring check valve (Autovent) to prevent a potential siphon from forming and draining the machine as it tries to refill. Any type of air-admittance valve, vent or “breather tube” will work as long as its at the high point of system and tall enough not to emit. The vent must be accessible (not contained within a wall) in case of leaks and for replacement.
Distribution System
Once your PVC distribution pipe exits the building (typically through a hole drilled in an exterior wall or down and out through a crawlspace) its typical to transition from 1” PVC pipe to 1” PE (Polyethylene) tubing, which is UV resistant and flexible. Tee’s off the main 1” line normally reduce down to ½” tubing that outlets the graywater into shields made from irrigation valve boxes. The shields protect the open end of the tubing from getting clogged by debris and have a removable lid facilitating access and maintenance. Take the most direct route as possible with the least amount of turns and maintain a slight downward slope or at least a level gradient, to minimize flow resistance. Because the discharge water from the laundry machine pump is slightly pressurized it can tolerate minor dips and rises in the distribution lines, unlike gravity-only systems (ie. branched drain) which must slope down continuously. Its important to NOT have every outlet in the system reduced down to ½” tubing because having at least one full 1” outlet provides a safety factor against clogging that could occur in the smaller tubing.
Infiltration Basins
The outlets release graywater into a mulch-filled infiltration basin, created by excavating out the soil and refilling with wood chips, gravel drain rock, or other chunky organic material providing open pore space in which the surge of graywater fills preventing it from being exposed to the surface (which is prohibited).
The 12 code guidelines
to follow for a code-compliant permit-exempt Laundry Greywater System.
1) Notification of installation of the system to Enforcing Agency (county or city permitting department, environmental health, public works, etc)
2) User can easily redirect flow to sewer
3) No potable water connection
4) The graywater shall be contained on the site where it is generated
5) Minimize contact with humans and domestic pets.
6) Water used for diaper washing and similarly soiled or infectious garments shall be diverted to the building sewer.
7) Graywater shall not contain hazardous chemicals derived from activities such as cleaning car parts, washing greasy or oily rags, or disposing of waste solutions from home photo labs or similar hobbyist or home occupational activities.
8) Graywater shall be directed to and contained within an irrigation or disposal field
9) Ponding or runoff is prohibited and shall be considered a nuisance
10) At least two (2) inches cover of mulch, rock, soil, or a solid shield covers the release point
11) Exemption from construction permit requirements of this code shall not be deemed to grant authorization for any gray water system to be installed in a manner that violates other provisions of this code or any other laws or ordinances of the enforcing agency.
12) An operation and maintenance manual shall be provided.
Estimating Graywater Production
Using the Code formula (1602.8.1) requires knowing the number of bedrooms in the house, which determines the number of theoretical occupants:
1st bedroom = 2 occupants
Additional bedrooms = 1 occupant
Add up the total occupants and then multiply the total number of occupants by the estimated graywater production per-occupant accordingly:
Laundry = 15 GPD (gallons per day) per occupant
Showers, bathtubs, and wash basins = 25 GPD per occupant
See the example at right for a complete calculation process for a four bedroom house.
Sizing Infiltration Areas
The area (square feet) of mulch basins needed is determined by dividing the estimated number of gallons produced per day by the soil type’s maximum absorption capacity (measured in gallons/sq2). Use Code Table 1602.10 at right for common soil types. See examples below for complete calculation for 2 different soil types with an estimated daily graywater production of 75 gpd.
Coarse sand or gravel: 75 gal/day / 5 gal/ft2/day = 15 ft2
Clay w/small amounts of sand or gravel: 75 gal/day / 0.8 gal/ft2/day = 93.75 ft2
Surge Capacity
The open pore space between the particles of wood chips, gravel drain rock, or other chunky organic material in the infiltration basins provides open space in which the surge of graywater fills preventing it from being exposed to the surface (which is prohibited). Approximately 40-60% of the volume in an infiltration basin is occupied by the refill material depending on the exact type used. By calculating the total volume of the excavation and subtracting the volume occupied by the fill material we can get a rough idea of the available surge capacity in Cubic feet and then convert that to gallons (There are 7.48 gallons in a cubic ft3).
(Gallons of estimated graywater discharge per day / 7.48) / porosity (expressed as a decimal) = Cubic ft3 of infiltration basin required
Ensure the available volume of the infiltration basin exceeds the calculated surge volume of the daily greywater production.
Labeling Requirements
To avoid future confusion Graywater distribution piping has to be labeled to identify it as being Non-potable water. The words “CAUTION: NONPOTABLE GRAY WATER, DO NOT DRINK” should be marked on the pipe at intervals not to exceed every 5 ft.
The 3-way diverter valve in the indoor assembly of the Laundry-to-Landscape System is also required to be labeled as to which handle direction sends the graywater to sewer or landscape.
Operation and Maintenance Manual
Required info:
Diagram(s) of the system and location of components
Instructions on operating the system
Details on start-up, shut-down, and deactivation
Applicable testing, inspection and maintenance
Contact info of installer/designer and component manufacturer
Directions that the O&M manual needs to remain with the building for the life of the structure
Other helpful info:
What kinds of soaps to use
A picture of the tubing before it is buried
