If you ever wanted to put in a quick and dirty greywater system, California law now allows you to use washing machine water in the garden. Constraints are: greywater must not come into contact with open air and you cannot store it, because it will smell within 24 hours. Showers are also legal, but are a different gravity feed system. Kitchen sinks are still considered blackwater, and not appropriate for greywater.
These notes are from a workshop with Greywater Alliance, and 10 of us installed a system in an Oakland home in about 3 hours. Most of the work is in digging the trenches (4-6 inches below the surface).
When you're planning where to put your drip lines, keep in mind that the water's going to be delivered to the garden intermittently, and can be a deluge. A typical top-loading washer uses 40 gallons per load, and a water-efficient front-loader 15-20 gallons. If you do all your laundry on the weekends, it can be 100+ gallons in two days, followed by a stretch of a week or more. For that reason, it's best to use this type of greywater system to irrigate trees or blackberry bushes. There are gravity systems for showers/sinks that operate and designed differently.
Laundry-to-greywater is the absolute simplest greywater system. It has no pumps, or filters, because they're a pain to maintain.
A greywater system isn't feasible if you have a high water table -- less than 3 feet below surface, because of the danger of contaminating the groundwater. This system relies on the washing machine pump to deliver water to plants -- so you don't have to deal with the gradient requirements of a gravity (shower) system, which is roughly making sure your pipe drops 1/4 inch each foot, to keep water moving.
How It's Done
1. From laundry machine
Attach three-way joint valve 1” to wall ($30) near and *above* the height of the washer.
This lets you direct the water either out to the garden or into the sewer. You must use a non-salty detergent like Oasis. If you want to use bleach or another non-plant-safe product, you'll want to switch over to sewer disposal.
Going into the bottom of the 3-way joint is dirty wash water.
Output from the T goes either to the sewer or to the greywater irrigation system.
- Sewer PVC pipe goes down (existing) standpipe about 2 inches. Do not make a seal; leaving it open means it won't siphon, pulling dirty water back into the washer.
- Second PVC pipe goes through wall/floor to garden, ideally immediately. To go through the wall, drill 2 test holes 1.5 inches apart using extra-long drill bit, and see if you hit anything. Use circular saw to drill 1 ½” hole, or round hole saw - Milwakee set is a good one.
2. Outside wall
- Install a 1½” Autovent - use 'bushing' to attach to 1” inside female adapter (threads will be on inside) PVC pipe. Autovent is another anti-siphon device, so system won’t pull the greywater back into washing machine.) You'll need to add a 1” barb by male adapter (need more info)
Putting PVC pipe together will require some tools, like a pipe cutter, and glue. For threaded attachments use 1/2 - ¾” teflon tape to seal connection. 3-4 turns. There is a correct direction to put on tape – clockwise and away from you.
Tubing
Schedule 40 PVC pipe above ground in/out house (avoid Class 20 – it’s crap); pipe cutters, Gorilla Glue is less toxic. Use 1.25” plastic straps (not metal) attached to wood wall.
3. In the garden
Blue lock tubing underground (“HDPV” high density polyethylene) Can also use more flexible black tubing, but less resilient/more prone to damage
Dig ditches ~4 inches below surface (may be easier to move dirt than pipe)
1” mains to mulch shield
OR
1” mains to ½” branches to mulch shield
Must have mulch shields at the end of every line.
You can pay $3-4 for mulch shields or you can create your own out of plastic 1 gal pots
Wing it in terms of water flow. There are thingies to put on the end of the line that allow you to slow the flow through the endpoints. You can always pull your lines higher to slow down the flow, or dig deeper to increase output.
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