Water filling the fresh water tank

[oxcamper]

I have a Salem Hemisphere 2015 282RK. We are at a seasonal site and are connected to the fresh water supply and do not use the fresh water holding tank or the water pump. I do winterize the fresh water system and pump even though we don't use it, and when flushing out in the spring, I leave the drain valve open to the fresh water holding tank.
We've been at this site for 4 seasons and I've done the same thing each year.
I opened up the camper this spring, and hooked up the fresh water hose to the "fresh water" connection and flushed out the tank and pump. Then,, as normal, I connected the water supply to the "city water connection" and flushed out the antifreeze in the rest of the lines. Everything was good.

About 2 days later, I heard the noise of a water leak splashing on the ground and discovered water was flowing out of the drain valve from the fresh water tank. Now nothing is connected to the tank inlet and there should be no water in the tank.

My only guess is that water from the pressurized side of the lines is back flushing through the pump into the holding tank. There is a filter on the inlet side of the pump (conveniently ) located under the sink behind a panel. I do not see any check valve, unless its integral to the filter. Other than the connection on the outside of the trailer to fill the water tank, there is no other inlet to the holding tank other than the pump hose.

I have not taken the pump out to inspect it. The pump is a SHURflo 4008 by-pass pump.
There are no water leaks in the trailer. If I let the tank fill and run the pump with the city water shut off, all works as it should.
Why this all of a sudden happened this year I don't know unless there is a some debris or deterioration in the pump workings as a result of age or no using it.

Has anyone had this or heard of this situation?

I am thinking of putting a shut off valve on the outlet side of the pump where it connects to the water supply to keep the water from back flushing through the pump. Since we don't use it on any normal basis, I would just have to remember to open it if and when we do need the fresh water tank.

Does this sound like a reasonable solution?

[Capt. Mike]

There is a diaphragm integrated into the pump. Often, it gets a little dirt or some other foreign material in it, and holds that diaphragm open. Try shutting off the city water supply, turning the pump on, and running a little water from the fresh water tank through the pump. Do that several times - on, off, on, off, etc. - to see if that "flushes out whatever is lodged in there, affecting that diaphragm.

That usually works, but if it doesn't, maybe a little compressed air (very low pressure) through the pump. Otherwise, you are looking at removing the pump and rebuilding or replacing it. they make rebuild kits for water pumps because this is a fairly common thing.

[oxcamper]

thanks Cptn, It's kind of what I figured. A piece of dirt or debris is holding it open and not seating properly.
I did do that once, but I'll give it a couple more tries and keep you posted.

[Dwilcox]

I have a valve on the inlet side of the pump. If in city water I leave it off. If I did not have one I would add.

[kcmusa]

https://www.youtube.com/watch?v=6wsPiA09mXQ

[Volvodriver]

Same deal today on our 35ROK Sandpiper. We full time in ours and noticed this morning water coming out of the over flow and getting the gravel wet. Hooked to city water but the fresh tank says full and we haven't put any in fresh tank since April 3rd when we left Arizona. Going to run pump as Capt. Mike suggested and see what goes. We carry a spare pump but its a small chore to get to it.

[oxcamper]

Just got back from ACE hardware with a straight. 1/4 turn pvc ball valve and installed it on the outlet side of the pump. I'll try to post a pic.
Works great-- all fixed. Keeps the line water pressure off thepump diaphrams

[oxcamper]

Photo of shut off

[JimMorrell]

I have a 2014 Wildwood. Our second season, while connected to city water I found the tank overflowing. Turned out the backflow diaphram on the water pump was bad and allowed city water to flow through the pump to the fresh water tank and out the overflow. Not an unusual problem.

[Bargeman]

Ditto to all...

Brand new 2017 coachmen Mirada 35ls and as soon as we got home with it, set up camp, connected city water, kept hearing it and finding nothing... fresh tank fills... overflow... not worth taking entire MH to dealer for warranty on this...

1/2" threaded ball valve and close nipple, and leak lock.... added to the pump suction side... tested... good to go!!!

[Bargeman]

Old school navy training: never rely on a check valve - holds true...

[levert]

Same problem with my sandpiper. Went to camping world and bought an in line check valve and installed it on the output side of the water pump. Took all of 10mn. solved the problem.

[RussPastuch]

Those pumps are ridiculously easy to take apart and put back together, and actually still work. Not a bad idea after years of not use to open it up and give it a cleaning.

[Volvodriver]

It was debris in pump. Ran the fresh water through the sinks and plenty through the toilet. Checked the pump and presto no more water overflow. Thanks Capt. Mike.

Dave

[Comanchecreek]

Seems to be a common problem on new rigs. I think the manufacturer must leave as much trash in the plumbing system as they do inside of the trailer. I had read about this problem on this forum so was armed with potential fixes when it happened. I had water running out of the water tank drain. I disconnected the city water. Put a few gallons in the water tank. Ran the pump for a few minutes. Cleared out, no more problem. We'll see if it arises again. Never had this problem with my old rig.