Separating Fresh Water From Pump Toilet

geraldooka wrote:
Thanks for the advice folks. I believe there is a check valve of some kind installed now. It's a large unit with a ball valve shut off attached to it designed for residential plumbing I suspect though I can't be exactly sure as there are no markings on it as far as I can tell. I should note that unlike modern trailers our water system is not under pressure at all times when the pump is on. It's old school. Of course the toilet is so old I can't find any info on it on the net.

Do you have an air pressure water system with a pressure tank? I still have that system and like it so I'm not going to install an on-demand pump.

I would bet that the valve fitting on the toilet is a vacuum breaker valve. Look for a vent on the fitting to confirm.
If it was me, I'd confirm what type of fitting is on the toilet (you could do that by removing the upstream connection on the toilet supply line and see if water readily flows from the supply line, if it does, you don't have backflow prevention. If it doesn't all come out immediately, you're golden) and install another check valve upstream from the toilet valve. That should insure that if the system is pressurized once, there is still a small amount of water in the supply line if the system pressure is removed.