This is a typical simplified water flow diagram for the RV's...
You can see where ONE WAY VALVEs are handy to have...
Google Image
The newer trailers all seem to now have a water panel it seems for using the different methods for water flow...
The basic concept is when using city water the on-board fresh water tank and associated water pump is by-passed using the one-way water flow valves...
I think my very simple water flow setup between the fresh water tank and the water pump must have the one-way valve inside the water pump motor. I have never noticed a one-way valve in-line...
Roy Ken
