Fresh Water Tank Over Flowing

[DJLs]

Hello Owners!
We have a question to our fresh water tank. When attached to a water service, we are having a slow back fill to the fresh tank. The back filling causes the fresh tank to overfill and drain off the top. This overfilling is by design, which is good. We have the fitting set to water service and not fill tank. Any ideas? Thanks All!

[creativepart]

This is a common issue. There are a zillion posts on this on RV forums, and on YouTube.

Your water pump has a built in check valve to prevent water from a city water connection flowing back into the fresh tank. All it takes is a spec of dirt in the check valve to allow a slow leak into the fresh tank. And, when full your fresh tank will send water out of an overflow valve on top of the tank.

The easiest solution is to turn off your city water at the spigot and live off of the fresh tank until you use up the water in that tank. Then go back to your city water supply.

Many times this is all you need. If it reoccurs do the same thing again. If it keeps happening you can easily remove the water pump's check valve and clean it. OR you'll find check valve rebuild kits for cheap as well on Amazon.

Some buy a small plastic check valve at Home Depot, etc and place that in the water line - as to where to put it, I've always been told to put it on the output side of the pump... but others claim it should be on the input side of the pump. You'll have to figure that out for yourself.

It can be other issues in a motorhome like your Vista. You have a diverter valve in your water compartment that you use to set water to City or Fresh tank fill. That valve can leak and or fail. This is not as common as the check valve problem I mentioned above.

Always make sure you have a pressure regulator on the campsites water supply bib - I set mine to 50psi. When the campground has high water pressure it's not good for the pipes in your RV - and it can be the cause of the check valve problem, as well.

[Morich]

One of the more frequent problem is that the check valve at the watyer pump is not sealing well. I tried to look at the parts drawings here:
https://catalog3d.winnebagoind.com/menu/Parts.htm

But when looking at the tubing behind the plate at the wet bay where the hose connects it becomes such a spiderweb of tubing that I was not able to trace out the exact flow in any way that I could snip a picture to show you how it can do this.
Maybe word description will work?

What we often find is that there is a path for water to flow to the tank when a valve is set correctly as you mention and then a different path when the valve is set to normal. On that second path there is a small plastic type "check valve" which is a pretty high class name for a simple flap that falls into place to stop flow from that direction!
What happens on older is that flap gets stiff as it degrades and it no longer fully stops the water going to the tank.
That requires replacing the flap portion of the pump. A small kit of parts and not technically hard to do but getting it out and back in can be a trick, depending on location.
On a newer RV, I might be more inclined to think the flap has some bit of debris stuck in the opening!!!
One way reported to clear this is to turn water on/off in sudden bursts to try to hit the debris with enough force to make it move!
I would first go for trying to make it clear by turning the faucet pressure on/off several times and also hitting the pump severla times hoping for a bit of luck?
Newer Rv tend to have small scraps of plastic at different points where holes and tubing have been installed and this junk can get into just the wrong spot at times.

For more info a search for "RV water pump check valve" can turn up lots of videos and articles on what you may find.

Hope for the best but be ready for the worst? Good luck to you!

[DJLs]

Thank you for the reply and advice! We’ll give this a try.

[DJLs]

Thanks for your reply and advice. I’m with you that it might be debris. I will cycle values and give it some water bursts.

[Morich]

Just for Sunday exercise of the brain, I went back to see if I could better spot how the water flows from the inlet to the pump and came across a bit of info that is different than many RV I have looked at.
But it does explain why I could not trace the flow of the lines on the other drawing!

They use, not one but two manifolds and that brings lots of tubing into a small space for trying to draw it out and make it clear. So I went to the plumbing drawings here:
https://www.winnebago.com/Files/File.../000203185.pdf

With a different view and thinking of what has to happen, I now see what they were trying to show. A cold line comes into the manifold for cold and goes out to the RV parts needing cold water.
Then there is a second manifold which takes hot water in from the water heater and splits it up to send out to places where we need hot water.



No big deal and nothing new but it sure made it hard to spot what was going on at first look! Not used to seeing that on RV!

[deckape]

On my Forza I have to turn city water off , change valve postion then turn water back on . Valve will leak thru valve and slowly fill water tank if I switch it without turning off/on

[Bo Walker]

I've corrected this problem on my motor home. It's not a hard repair job if you are the least bit handy with basic tools.

[jerichorick]

Originally Posted by DJLs

Hello Owners!
We have a question to our fresh water tank. When attached to a water service, we are having a slow back fill to the fresh tank. The back filling causes the fresh tank to overfill and drain off the top. This overfilling is by design, which is good. We have the fitting set to water service and not fill tank. Any ideas? Thanks All!

I'm not familiar with your coach but a wild guess is you have a selector handle (valve) for "CITY" of "FILL". If it is all plastic there is a very good chance this is where your problem is. I have had to replace these with brass.

In Winnebago's wisdom, they installed a valve with weak parts that break under city water pressure when the valve is operated. The operator manual, in my case, says NOT to turn the valve when city water is on.(????)
The valve is easy to take apart. I suggest you have a brass replacement handy before you do.

Take the handle off, unscrew the knurled nut and pull the valve cartridge out. Look for any damage or debris.
Have a good plan and all parts needed before you start. This can make camping very inconvenient if you can't get the water back on in a timely fashion.

The valve is available at most HD, Lowe's and possibly a local hardware store.
Happy trails.
Rick

[DJLs]

Hello All. Thanks for all the comments and advice. We’ve been out a couple of times since my post. Cycled all the systems a few times and the back flow to the tank has stopped. It was likely debris. Thanks again.

DJLs in AZ