I figured what was happening is the check valve was leaking due to a dislodged worn or damaged o ring.
Rv check valve leaking.
Go whole hog and replace the pump itself.
The valve is designed to let pressured city water enter the rv s plumbing system when hooked to a charged hose bib via your water hose in an rv park and prevent the water pump from pumping water out of your potable water tank onto the ground when not hooked to a charged hose bib.
An occasional rv will be found that has a 3rd dump valve and even 2 separate dump hookups.
It s hardly an owner friendly arrangement but i have seen it.
If nothing poured out repeat the above steps for.
Dislodged check valve seal under the mesh screen in your city water inlet there is a little valve that is meant to prevent backflow when using your water pump.
To determine which valve is leaking you should have your rv waste tanks empty.
If you do not want to fool with broken or stuck dump valves.
Add your own 1 way check valve to the water line on the inlet side of the pump.
Our city water connection has been weeping water when using the onboard water pump and fresh water tank for dry camping.
The leaking issue may be coming from a cracked pipe or a loose connection.
Unfortunately if the valve gets pushed in while the system is pressurized the seal on the valve can get pushed out of place very easily causing fresh water to leak out of the city.
For those just entering the rv lifestyle there is a check valve behind your city water hook up.
Did any water leak out.
Inside is a plastic check valve plunger a spring retaining clip and small rubber o ring.
This will help keep the dump valves from becoming sticky after they have sat for a long time.
Many moons ago the owner of the site called me on a sunday evening to help me.
I had a plumber at home depot tell me you could not use pex clamps on a plastic fitting yet my rv service manager says the rv industry has been doing just that for 20 years.
Check amazon or rv water filter store for options.
It is a messy job but someone has to do it.
I bought a 3 years old 5th wheel and found several leaks in the plumbing behind the dividing wall in the basement.
There are worm gear clamps and pex used.
With the wastewater valves closed and the black cap off place a 5 gallon bucket under the sewer drain port.
Wait about 30 minutes then head outside and slowly uncap the waste pipe.
Close all valves then go back inside the rv and add several gallons of water to just one tank.