I've been operating a "single plastic drum and leach field" system for 7 years for dumping our trailer's black tank. It's slowly clogging up, probably because the whole tank-load throws solids and paper into the leach field. I'm now going to keep that system for the grey water, with the valve permanently open, and install a new system for the black tank. I will copy the principles of a system I saw in a 100 year old home in Maryland. I will install one plastic barrel as described in the earlier posts, but this wil be linked at the top to the top of a second plastic barrel, surrounded by rubber mulch/stone/gauze. This barrel will have dozens of small holes drilled all over it. This second tank, the "soakaway", will normally be empty. When the 35 gallon rush goes into the septic primary, 35 gallons will spill into the 50 gallon empty soakaway via the submerged outlet, from which it will "soak away" over the next couple of hours. I will put an air vent in the top of the soakaway.
I am a great believer in home-built septics. I have been using one for my home in England for 20 years. It has never been pumped out, and it has never smelled bad. I can detect no grit in the primary. No enzyme or other similar products have ever been added. We do not use a waste disposal unit in the sink, in order to minimize the biological oxygen demand on the septic. With a single home septic, very close control can be kept over what goes into the system, and this is, in my view, the reason for its success. For environmental reasons I prefer my single-home septic to our local public system which pumps "treated" effluent into our local river. It does, of course, require from users an understanding of the principles involved in septic systems for them to operate effectively.
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."