Home: Kitchen: Sink
sewer/greywater double sink   (+2)  [vote for, against]
Dedicated sinks for greywater bliss.

One side of a double sink tends to be used for washing, and the other for rinsing. The standard installation involves joining the pipes from the two sinks inside the cabinet space below, and running a common pipe to the sewer. What a waste waste!

I propose connecting the washing sink to the sewer, and the other sink to a greywater outlet.

Why? Because some things, including potentially infectious materials and high concentrations of detergents and salt, are best sent to the sewer, while rinsing water and most food waste such as coffee grinds are great in the garden. A dedicated sewer sink and garden sink would be more intuitive and simpler than other systems, such as manual diversion valves.

A garbage disposal unit in the garden sink would be appropriate too.
-- spidermother, May 01 2011

Composting_20Convenience_20Appliance [spidermother, May 01 2011]

Compost_20disposal [spidermother, May 01 2011]

My humble effort in ths direction. Shower_20water_20salvager
[bungston, May 04 2011]

You need a way to separate the solid waste from the liquid gray water, then a place to store the gray water for irrigation. The whole lot needs to be vented or otherwise accommodated in terms of preventing siphon in both directions. Coffee grounds and grease will form a brick if allowed to mingle. The volume of water that passes through the system will either be making very weak compost tea, or stripping all the soluble nutrients from your compost. If we could just commit to sustainable detergents I suspect that 100% of sink water would be gray water (with a mechanism to separate solids) and with some processing could be used as direct irrigation in low traffic areas. In the same way I see shower and bath water as intuitive flush-water for toilets with only minimal treatment and then diverted to irrigation. Seems to me if this was implemented we could sustain our gross abuse of potable water for many years to come.
-- WcW, May 01 2011

I once had a related idea for a looped shower, where one could set the shower to rinse you for 1-3 minutes, and then when you are sufficiently clean it would begin to catch the water going down the drain, and loop it back up Allowing you to enjoy the therapeutic benefit of a 30-40 minute shower while only using a few gallons of water.
-- bob, May 02 2011

it's going to get cold really fast.
-- WcW, May 02 2011

How to get a head? (Richard E. Grant) May I suggect a sepecific gravity pump?
-- 4whom, May 03 2011

[WcW], My opinion on greywater is that if you need storage tanks, separators, pumps, aerators etc, then it's probably not worth it; you are trying to reuse a relatively low value resource, so there is no point committing high value infrastructure and energy to the task. If it needs such processing, send it to the sewerage farm; you'll never compete with their economy of scale, unless you are off grid.

For years now, I've been washing dishes in a basin, and emptying the sudsy water and anything else I don't want in my garden down the laundry trough (sewered), and letting everything I consider garden-safe down the kitchen sink, which simply runs into a small patch of fruit trees via a straight length of PVC pipe.

You couldn't get much simpler, and it works perfectly, with about 15 minutes maintenance per year, mostly to cut a small channel to spread things out a bit more. I checked it today; there's a thriving population of composting worms, and vigorous, healthy roots growing up through the composting waste. It has never produced any unpleasant smells, and has been far less bother than the sewered plumbing.

A more complex system could hardly be better, and would probably be much worse.

Gardens are like sponges, and thrive on any inputs of water, organic matter, and nutrients, unless they are greatly excessive. Unless you are trying to run it like a hydroponic system, there is no need to fuss over the exact ratios.

I agree that it would be great if all water could be reused on the garden, but as things stand, there are some things in waste water that do more harm than good. One brand of clothes detergent that proudly says 'greywater compatible' on the front, says in fine print on the back to use the rinsing water only! Detergents contain lots of sodium, and seem to create boggy muck rather than beautiful rich soil, maybe because of their effect on surface tension or ion exchange.

[bob] The shower thing has been baked, exactly as you describe it. It was featured on "The New Inventors" (Australian TV) maybe 4 years ago. I think it had a heater inline, and a manual diversion valve. Even if energy is used to maintain the temperature, it would be less than that required to heat fresh water.

[4whom] Has potential...
-- spidermother, May 04 2011

Sink water as flushwater would be so bakeable in large public washrooms: divert drain from ladies washroom sinks thru the wall to floor mounted urinals on the male side.

Large greywater diversion systems would be well suited to casinos and hotels in the desert; prime examples would be the reservation casinos, which must sustain landscaping.
-- bungston, May 04 2011

random, halfbakery