Q. Mike: We are in the midst of yet another very bad drought, and have been doing our best to re-use as much household water as we can, mostly by bucketing our shower/bath water out to the plants in our garden. Will this water harm the plants or soil, as it does contain some soap? Many thanks.
- ---Sue McCluskey in Canberra, Australia
- ---Lynn; near Nashville, in Middle Tennessee
- ---Mary O. in Philadelphia
Art Ludwig is THE expert on this topic. But his website, Oasis Design, is packed with so much information I felt a little overwhelmed, so I begged Art to give me a primer on the topic. Here's his stripped down advice:
- Start with the 'low hanging fruit' in your water world: Your washing machine. The water is high quality and its already under pressure as it leaves the washer, so all you have to do is direct it into a holding, or 'surge' tank, from where it will immediately travel via a hose to the plants you wish to water. (You'll find free instructions and pictures here.)
- That outdoor surge tank is only there to slow the flow, not for storage. Have a hose in place under a big tree or in the center of a garden bed to use the initial flow, then move it around until you use up all the water.
- Although easy to use because they're elevated, Art says that sinks are problematic. Bathroom sinks just don't produce enough aqua to make it worthwhile, and what Art calls the "dark grey water" from the kitchen sink would foul a surge tank and clog up the hose.
- You could run a pipe to take kitchen sink water directly to outdoor plants (I'll link to a great story where such a design rewarded a homeowner with a 1500 lb harvest from a single pear tree), but Art suggests you run what he calls "this great, compost-filled water" through something called "a sealed, subsoil infiltration galley" instead. Luckily, this is all described in his book "Create an Oasis with Greywater".
- Bathtubs and showers are harder to harvest, because their drains are at ground level, but if the house is up high and your garden is down low, by all means, use this water, says Art; its very high quality and there's a lot of it.
- In a really dry clime, plumb your washer, bath and shower water to always drain directly out to the landscape. Otherwise, install a diverter valve (a fixture that allows you to send water down the regular drain or divert it elsewhere) to send water to the outdoors only during dry times.
- Buckets? Go right ahead, but carrying dripping water through your house and out to plants gets old fast, warns Art; and it generally doesn't provide enough water to make it worth the considerable physical effort.
- Soap choice can be crucial for long-term success. You'll find lots of lists of good (and bad) greywater soaps online (just search the topic) and in Art's book, "The Builder's Greywater Guide". In general, Art says to choose liquids over powders (sodium salts are used to make powders dry) and avoid products that contain chlorine, boron or sodium. (Chlorine bleach is bad for the environment in any form, so I hope this will get our Tennessee listener to go Cold Clorox Turkey; Art says that if 'bleach' you must, hydrogen peroxide is an acceptable alternative.) And if you want the very best, Art once designed a line of cleaning products that actually degrade into plant food; a company called Bio Pac now markets those "Oasis" brand products.
- WE REPEAT: Don't try and store greywater for future use! Art warns that it will quickly go bad and turn into stinky, nasty "black water". But you can safely harvest and store rainwater for release later on. (This topic is also covered in depth on the Oasis website.)
- Don't try and use greywater for drip irrigation; it'll just clog things up.
Elsewhere, registered plumbers will probably refuse to do this kind of work, so you'll have to do it yourself; get some plumbing handy friends to help install the splitters and surge tank so it gets done right. Art's book "Create an Oasis with Greywater" contains all the instruction you'll need to turn your indoor grey into outdoor green.