Potable water tank filling unexpectedly

[Red Sky]

2014 Cambria 30J. With shore water fill valve in rear storage compartment on NORMAL, the potable water tank level rises slowly (maybe 2-5 gals/hour). I replaced the shore water TANK FILL/NORMAL 1/4-turn valve (thinking it might be leaking past the ball). That had no effect. All valves in water manifold under bed are aligned correctly and I have had no problems for 2 years of operation until now. Have not done any work on the manifold. (While checking the manifold, I noticed the pump strainer was loose & dripping, so I tightened it.)

The potable water pump has “bypass” circuit. That could be leaking backwards past the internal pump check poppet valve thru the pump-tank suction line into the tank. So I checked that by shifting the 3-way pump suction valve to align to the open-end hose for chemical addition and over a couple of hours I watched for water backing up in the open-end fill hose. That is not the problem.

Any suggestions on the source for the unexpected water filling the tank?

Thanks.

[creativepart]

It’s probably the check valve built into your water pump. They get weak and or a tiny pice of grit and let water pass which fills the fresh water tank. It’s super common.

Many times it’s temporary or intermittent, but you may need to clean or replace it. Rebuild kits are available on Amazon and it’s an easy job.

First, turn off the city water and use up the water in the fresh water tank. Then switch back to city water and see if it continues filling the fresh water tank. Make sure to not run the pump when using city water because that seems to make things worse.

You can remove the check valve, it’s built into the pressure switch on the pump and see if it needs cleaned if need be as well.

Some folks circumvent the problem by adding a new check valve just upstream of the pump for a permanent fix.

[Red Sky]

Thanks. I think you are right. Even though I tried checking the pump internal bypass possibility (but saw too little water backflowing to "confirm" it to my satisfaction), you say (and I agree) it may be intermittent. It may be a sign of the pump water side needing overhaul. But I will just keep an eye on it and pursue the overhaul when/if it becomes too annoying (i.e., tank overflowing onto ground in copious amounts ).

[creativepart]

Shurflo water pumps are super easy to work on and they have easily replaceable components. For instance, as along as the motor still works good you can buy a bolt-on "head" that includes everything from the motor forward and, in essence, totally rebuild your water pump for little money. It's held on with 4-bolts and it's already adjusted and ready to go. It takes less then 20-min to replace.

As I said, many install an in-line check valve between the water hose and the pump inlet. Using a check valve with 1/2" barb connections it too is a super simple fix.

My water pump was filling my fresh water tank intermitantly so I bought a check valve repair kit for $9.

https://www.rvplus.com/shurflo-model...94-800-03.html