Kitchen sink only, direct pipe 10 feet of length with no bends diameter of 1.5" at 1% slope discharging to a valve box (12" X 8" X 10" deep) 1/2 filled with pine needles, discharging to a pine needle filled mulch basin planted with cedars, grape vines, ferns and comfrey. Note: the p-trap under the sink was eliminated when disconnected from septic.
Piping is not glued, friction fit only, to facilitate any system maintenance such as cleaning, modifications or discharge location changes. I have not noticed any leaking of the drains, interior portions are located under the cabin which is easily accessible for inspection.
When we installed a grey water system to handle the flow from our kitchen sink at our summer use cabin - we significantly changed what we allowed down the drain.
Prior to the greywater system: we were extremely careful about anything going down the drain as we wanted to minimize impact on the septic system. We were physically removing used dishwashing water via plastic basin each time we did dishes.
Since installation: Anything that can fit down the drain screen is encouraged, including plate scrapings during a rinse - meat, dairy and oils being the exception. Our coffee grounds are also sent directly down the drain and provide a cleaning/scouring function during their disposal.
This has eliminated having to scoop out sink drain leftovers after dishwashing and facilitated disposal/composting of coffee grounds. The valve box where the greywater is discharged is checked periodically and pine needles added occasionally to cover up any visible food scraps. I have found that this system is composting quite nicely and every couple of months I am topping up pine needles / not having to remove excess material.
We are going on 3 summers now and have not noted any pipe issues or vermin issues in the mulch basin.
Pushing the Limits: What about modifying or removing the sink drain screen be removed to allow for additional compostables to be sent directly for composting - I am picturing that the valve box could be replaced with something larger to act as a composting vessel to receive all suitable food scraps. Careful management would be required to ensure appropriate materials only. Compost materials would require some sort of processing (cutting/shredding) or larger diameter pipe could be considered
Many kitchen sinks look onto the garden - the short pipe runs, elevated nature of the sink drain and regular water use would facilitate disposal of food scraps directly via this method. Maybe this is an option to include a version of a compost chute from another thread here? compost chute
Sounds like you have a great system! Since you don't have any bends, and the pipe run is short, I think you can get away with putting a lot of organic matter down the drain, as much as will fit
The potential issue you may encounter, or other people will encounter if their system has bends and a longer run, is the pipe will clog up over time. It's not hard to unclog so long as there are access points, but it is a little extra maintenance. Kitchen greywater can sludge up and then blog the pipe after a few years.
In general kitchen greywater outlets are a great place for composting, there is so much biological life under the outlets. The soil under the mulch under my kitchen outlets is swarming with earthworms.
Regarding creating a chute for all the compost as part of the kitchen greywater system: I think the amount of effort it would require, to chop up the food and manage the compost area outside, might be more than just maintaining two separate systems (kitchen greywater and regular compost). But I think it's a great idea to try out! Let me know how it goes. ,
Co-founder: Greywater Action, www.greywateraction.org
Author: Greywater, Green Landscape, and The Water-Wise Home: How to Conserve, Capture, and Reuse Water in Your Home and Landscape
P Lyons wrote: Compost materials would require some sort of processing (cutting/shredding) or larger diameter pipe could be considered
You don't mention whether or not you have electricity? If you do, is there room to install a garbage disposal before the pipe goes outside? It would definitely process your compostable materials down to a small size that would break down quickly. If you don't have electricity, you could use a hand-crank food/meat grinder to do the same job.
God is good all the time!
Diego Footer on Permaculture Based Homesteads - from the Eat Your Dirt Summit