[JRTJH]

First, does the system operate properly on city water? If not, it's not the water pump. If it does operate properly, then I'd suspect you have a valve in the convenience center improperly positioned. Either the winterize valve (draws antifreeze or draws water from the Fresh Water Tank) or another valve, possibly the tank fill valve ??? If your trailer operates properly on city water, I'd suspect the winterize valve.