We just bought some vacation property in the desert and want to run an additional sewer line. There is a 2 bedroom home and a 1 bedroom studio on the existing septic system which is in good condition and recently pumped.
What our plans are is to have a spot with three RV trailers with full hookups. Water and electricity is no problem, but we need to run a sewer line. Our thought is to run a main 4" abs pipe from the center trailer (96') and tap into the existing main line from the house using a sweep tee. The other two trailers will connect to the "trailer main" also with sweep tees.
Does this sound like it will work alright?
Sometimes I hope to be wrong, and maybe that is the case here! It sounds like you have enough depth for slope, and a 1500-gallon tank (good for a three-bedroom house here where I happen to live) is not a small one. So, maybe give your plan a try and see what happens. Also, it would be best for the RV holding tank/s to be allowed to get fairly full before dumping ... maybe once per month (and in some kind of rotation, if necessary). Otherwise, you will end up with solids stuck to the bottom/s of the tank/s when there is not enough liquid to float things and carry them on out. I once learned that the hard way -- no pun intended -- but maybe you already know about that. And of course, it can be helpful to dump the sewage tank prior to dumping the grey-water tank so the second can assist in moving the first on down the line.
IF the RV's use that blue holding tank treatment it will kill you septic tank almost immediately. There is a big gap between what will work, which seems to be what you want to do, and what is legal and proper, which would cost much more and is what a plumber would have to do.