I am re-building our greywater system right now, and have just converted a 120L plastic stock trough from a totally failed grey water "filter" into a mini septic tank. So far (one week only) it is miles better than the festering old filter ever was, and I have great faith that it will continue to serve us well. I struggled to find any info on sizing septics though, and conventional wisdom around these parts seems to be to take the design loading rate for the household per day and add 2000L to get the recomended size.... So that makes it massive.
My question for Feidhlim Harty is: How small can you go with a septic in your opinion? Below a certain size does it stop being a fully functional septic tank and just become a still pretty handy settle/float tank?
I really like the idea that you can pair up a
compost toilet with a mini septic and be dealing with your stuff in an efficient effective manner with a minimum of materials and earth works. I am going to use another stock trough as a mini wetland to clean the water up a bit and use a syphon to dose a simplified disposal field. The bath will dodge the septic tank and go straight to the wetland to avoid overwhelming it - or it could go to its own little swale type drain, not sure but either way it won't be dumping into the mini septic and wrecking havoc there.
Will take some pics to share tomorrow.
James