Originally Posted by Danjo
I am concerned about backflow from the toilet fresh water supply line. Is that something to worry about? I just picked up 3 check valves. I was planning on one for the toilet, one for the pump (I saw your other reply just now about the pump having one) and one for the municipal water inlet
Since you've already got them it wouldn't hurt to install them. The check valve on the municipal supply would need to be installed at the camp faucet end of your supply hose to protect the camp water supply. The one downstream of the pump may
restrict your flow a bit but otherwise no worries.
Many cities require backflow preventers (basically a check valve) on outside home faucets because watering hoses can heat up in the sun and pressurize the hose which could force potentially contaminated hose water back into the home water pipes and possibly back past the water meter and into the city water mains. The RV toilet would have to somehow pressurize it's flush water tank and overcome the valve in the water module to force flush tank water back into the water supply line. Unlikely but not impossible. The chances of being eaten by a lion at noon on main street may be a billion to one but once would be enough.
If your toilet check valve lowers the paranoia level then it's a good thing. I've done plenty of things that weren't strictly necessary but made me feel better about a project.