City water supply issue on a 2007 Jayco 345BHS.

Good catch, I'll remember that. The only trouble we ever had with our 345BHS and water was that screen at the connection from hose to unit. We bought the unit used so it may not have been factory, but it sure worked better once I removed it.

Problem solved, in the city water connection on the side of the trailer is a small check valve. It has a spring attached and a little plastic keeper I think that keeps that connection sealed off for when you do not have a water hose hooked to it. That keeper had broke and allowed the plunger to go in and sealed off on the inside of the valve. I just pulled all the pieces out and will have to get a replacement when we get back home. Thanks y'all.

The only check valve inside the trailer plumbing that I'm aware of is at the hot water heater to keep the hot water from pressurizing and pushing back into the cold input line. If you are not the first owner then it's possible someone installed a backflow valve to the inlet, but usually the manufacturer does not.

If there is any type of in line filtering then there may be something there blocking the flow. The screens on the end of your faucets can get clogged with sediment but that would usually only effect one faucet at a time and not the whole trailer.

I would still try filling the freshwater tank and see how that works with the water pump. It may rule out a few other things.
Keep us posted as to what you find.

I tried the water out of the hose is good. I tried to hook dirrect and it did no difference. Pretty sure the trailer was over pressurized because the regulator had failed. Possibly some type of pressure valve tripped in supply in trailer???

Most likely your pressure regulator has malfunctioned. You might try temporarily bypassing it to make sure.

Try putting water in your fresh tank and using your 12v water pump to see if that works.