since we moved into this house, we’ve used our grey water from the kitchen sink to water trees. it’s a very low-tech bucket system. we also recently “upgraded” our washing machine drain so it goes into a barrel with a spigot connected to a hose that we move around to the trees in the orchard.
we felt great about all this until the trees that got the majority of our dish water started dying. oops. turns out most detergents, even those labeled “biodegradable,” contain salts that are very harmful to plants when they build up in the soil. where we used to live, in eugene, we probably could have got away with using regular soap because there’s enough rainfall to flush a lot of the salts away. but here in joshua tree, that’s not the case (last year we got 2 inches of rain, that’s what vancouver got in the last 3 days!). the salts just build up until the soil is totally toxic to plants.
it’s pretty hard to reverse the damage done by salts once it’s done, but we can stop adding salts by using grey water safe, or better yet, biocompatible detergent. i was already buying biodegradable soap, thinking it was grey water safe, but those labels are misleading. biodegradable means something will break down, but what it breaks down into may or may not be toxic to plants. biocompatible means that it breaks down into plant nutrients (no salts!), and makes plants happy. yay! i just ordered oasis bicompatible laundry detergent and dish detergent. so far they seem to work fine. i’ll post a review once i’ve used them for a while. even if they don’t work quite as well as regular detergent, i’m willing to sacrifice a bit of performance for being able to recycle what amounts to about 55 gallons of water a day (that’s 45 for laundry and 10 for the kitchen sink).