You are a hard act to follow. Nice work! Can i make one small comment? After I sweat a joint I take it over to the wire wheel and brush it. The solder comes right off the pipe and you have a really neat joint and the copper shines. This is looks only and yours is a superb design that I would follow without reservation. Again, nice work.
I have a addition to your system that might be considered by some. I will install a "return line" from all hot water fixtures that goes back to the fresh tank. The line is connected to a push button valve that is connected to the hot water line at the fixture. When you want hot water you press the button for a few moments and release. That brings hot water to the fixture and you never have to wait for the hot water to get there and waste water into the grey tank. The other benefit is that I can flush the hot water tank into the fresh tank and increase the fresh tank's temperature in winter. Originally I was going to use this as my fresh tank heater for freeze protection.
I don't plan to configure my tanks as you did. I want my heated fresh tank on the bottom and my waste tanks on top. Taken together my waste tanks will be the same size as my single fresh tank. The toilet will drop into the black directly. With this setup i can heat the fresh and the heat will migrate to the other two and they need less heat. The bay can get by with less heat and the water is heated with shore power when parked and with propane heated water when in the boondocks. With everything in one bay I will have a true "wet bay". Insulated floor and sides covered with ply and all built onto that floor. Sound reasonable?
I am not worried about sloping the lines although I will do that if possible. I use air pressure to blow out my lines and I leave all fixtures open. I really like working with CPVC for some reason. Maybe because I have never had a leak or failure....old dogs and all that.
Hope this is of some use to you Grant, Thanks Gumpy Dog,
I considered the return line on the hot water, but after doing the calculations, I decided it wasn't worth the effort to install the return valve and lines. I used 1/2" PEX, which holds one gallon of water per 100 ft. of pipe. My longest hot water run is only about 12 feet. I find I need to run my shower about 20 seconds to get hot water to the shower head. I probably only waste about 2 cups of water. Had I used 3/8" pex, it would be even less. With conservation, we can last a good long time boondocking. My family of 4 just completed 8 days in the mountains, and still had nearly 1/4 of the 150 gallon capacities available. If you're parked with shore water and sewer, then it doesn't really matter at all.
I configured a single 150 gal waste tank, and 3 fresh tanks totaling 150 gallons. I added a heater to the bay, and I use compressed air to blow out the system in the fall. I found there was just no way to slope all the lines to a low drain point, with the filters, pumps, pressure tanks, etc. I don't want to leave it to chance, so I blow the system out in the fall, suck in some RV antifreeze, and blow it throughout the system. Works for me and my system has withstood temps down to about -30* for 3 or 4 winters now with only one issue (forgot to open an unused ball valve and didn't realized it had water trapped in the ball).
As I said before, the only thing I'd do differently next time would be to use 3/4" line from the shore connection, through the sediment filter, and into the fresh water tank. That would require a slight modification to the main manifold. I don't plan to change it now, though, because I would have to pull the three fresh water tanks and weld in new inlet fittings. I also have a pressure regulator on the inlet, which is probably contributing to the problem. It works fine the way it is, it just takes a long time to fill the 150 gallons.