Egon, I got the basic idea... My concern is over a small part of the system's hookup and function. If you are pumping out the final chamber of a septic tank and the exit pipe is located properly, the pumping action shouldn't stir the tank much, hence few solids or floating foamy junk should be drawn out and deposited in the leach system.
Same thing for my "lower" tank probably but a third chamber would make me more comfortable. If the lower tank were pumped into the outlet chamber of the upper tank I am concerned that it would stir the tank quite a bit and cause floating debris and settled solids to get mixed into the effluent on its way to leachdom. That is why I think I would like to pump the lower tank's third chamber directly to the leach field.
Yes, I am aware of back siphon action. My next door (hatch?) neighbor got me out of bed one morning at 0500 because his boat was sinking (we both lived on our sailboats next to each other in adjacent slips.) His boat was only a few months old and I had critiqued his plumbing when he gave me "THE TOUR" when first bringing the boat into the Marina. I was a volunteer vessel examiner with the U.S. Coast Guard Aux unit in San Diego for 10 years. I pointed out that his galley sink drain was Y'd together with his automatic bildge pump outlet and put to the same through hull penetration without a seacock. He assured me that the open hole at the bottom of the sink would break any syphon action.
Well, within just a few months his automatic bildge pump failed due to corrosion on the terminal strip (poorly located) so he used the manual override each evening and pumped til the pump cavitated (caught air) then switched it off and went to bed. On this occasion his wife had left the sink strainer in place with some vegetable peelings in it and they shut off the air flow. When he pumped the bilge out he charged the syphon loop. When he shut the pump off, the ocean began syphoning into his bilge. At 0500 when his wife's feet hit the floor she was standing in water and some of the floorboards were awash. (Note the floor boards are at least 6 ft above the bottom of the engine space and bottom of the bildge)
I kept an emergency pump with a 20 ft power cord and large aligator clips for connecting directly to a battery and a 15 ft discharge hose (about 1 1/4 or so ID). It was a Rule brand 1500 gal/hr unit. Luckily, his batts were not submerged, just his shiny new diesel engine. He was grateful for the assistance. It is said that the best bilge pump is a scared man with a bucket... but for only a little while.
Long reply but thought you might be entertained by syphon story. Many boats have also been in danger of sinking at anchor or tied to the dock because of anti-syphon devices on marine heads. They are a spring loaded valve that is supposed to open up and introduce air into an inverted "U" shaped half loop. the delicate spring gets fouled with "stuff" being pumped out and the rest is predictable.
I would think that a riser pipe from a "T" connection coming from the lower tank to the output line of the upper tank would vent to the surface. Would put a 180 degree turn in it so it would not collect debris or rain. That vent should prevent any syphon action.
I'm open for suggestions if you know of a better or easier way.
Patrick
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