Some rigs that have water pump adapters to winterize by pumping anti-freeze from a gallon jug can be used to reverse fill into your water tank if you have an outdoor shower hook up in your water bay. Un-screw the shower head off of the shower hose and screw the shower hose into the water tank fill fitting. Turn on water pump and outside shower and water should have enough pressure to push past the back flow valve. However, like most I just pour the bleach into the hose and attached to water spigot.
