Water tank fills "automatically"

stenzack · 03-19-2024, 08:47 AM

Hello friends,
We own a 2019 Sunstar and are currently set up near Tampa. We have been set up here for 3 months and have had no problems with any of the utilities.

Two days ago my fresh water tank began to fill with water, even though we have not used that water tank since leaving home three months ago. No valve settings have been changed. The tank fills even when the connection valve is set for city water connection. Thoughts or recommendations would be appreciated.

**creativepart** · 03-19-2024, 09:17 AM

This is super common. There are one or two main reasons.

First, the fix. Turn off your City Water connection in your RV site. Then turn on your water pump and live off of the water in your fresh tank. 90% of the time this is all you need do.

When you get to the end of water in the fresh tank turn off your pump and open the City Water spigot in your site. IF it fills the fresh tank one more time, try the above one more time. If it continues to fill the fresh tank when on City water then you need to look into further causes and fixes.

Here's the issue. In your water pump is a small check valve keeping the water flowing one way. Sand, lime deposits, etc can get in your water system and leave a small spec of dirt in the check valve. This lets City water slowly fill your tank. Using the pump and tank as I mentioned above "usually" clears the sediment and all is well. (Until it happens again sometime in the future.)

Another possible, but less likely cause is a bad City/Tank Fill diverter valve in your wet bay.

Some DIYers simply install an additional external check valve on their water line on the supply side of the water pump line. This generally fixes everything immediately but is a DIY solution that you'd have to manage.

In other words, this is a small hiccup, super common, easily solved and not a big problem.

stenzack · 03-20-2024, 02:48 PM

Thank you for the quick reply. I have followed your procedure for fixing this problem. Sadly, this has not corrected the issue. I have scheduled a repair service for this coming Monday, I will share with you the results Monday or Tuesday.

Morich · 03-20-2024, 03:32 PM

If looking for a DIY solution that would be far less expensive than shop work, changing the valve or even the whole pump, is one of the more common things to try.
Looking at the pump, you are likely to find a brand and model number on the pump.
This is often done to avoid any chance of the pump having been changed by previous owners.
Looking at the age of your RV, this may mean you know the history? Possibly you are the first owners and have the info pack for the RV? That might allow you to dig the info out of the books for the RV?
Then you have another choice on how you want to move forward. One can go as simple as buying a new pump of the same model or one can go for a repair kit which should include the rubber parts which likely include the check valve.
Getting the pump out and back are often the harder part of this as they can be in small spaces where it is tight to work. But the pump repair itself is not much other than unscrew the end and replace the parts.

This link should get you a lot of sites with possible info:
https://www.google.com/search?q=repa...hrome&ie=UTF-8

One reason that seems likely on the flushing not working is that the rubber parts may be nicked or damaged or just deformed a bit by some bit of debris left holding it open?

**creativepart** · 03-21-2024, 07:53 AM

No need to replace a pump. The check valve rebuild kit is under $25 and the task takes maybe 20 mins.

https://www.amazon.com/SHURFLO-94-80.../dp/B00XKZ31VC

Rossi6998 · 03-24-2024, 11:48 PM

Unless I missed it in the above posts, it could be the check valve in your city water connection (where the hose connects to your motorhome when parked and you are using city water). This happened to me a long time ago. The hard water or debris will cause the built-in check valve to malfunction. I replaced the water inlet connection (see link below) and everything was fine. It's a simple repair, fairly cheap ($20), and will not hurt anything if you are wrong. Good luck.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Bo Walker · 03-25-2024, 04:04 AM

I too solved my problem by replacing the check valve. When I discovered my fresh water tank overflowing We were at Flaming Arrow Campground in Cherokee, NC. I simply turned off the water hookup and used the pump until we got back home. Replacing the check valve was a simple task.

Morich · 03-25-2024, 08:48 AM

No need to start a disagreement but I think there may be some confusion on which check valve to blame?
I think it is the check valve at the pump keeps the incoming fresh water from going back through the pump to the tank.
If we think about the check valve at the inlet, I don't think it can keep city water from coming in to the trailer.
I see that check valve as keeping water from going OUT, not in. If there were a check valve at the fresh water inlet and turned to keep water from coming in, the hose would not be able to let water in to use.

This little drawing is the way I see the two check valves working.

Click image for larger version

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Fresh pressure water comes in the port but can't go directly to the tank due to the check (one way) valve blocking it. We get water to the RV!
Tank water has to come OUT through the pump check valve to the RV to get water inside. But we don't want that water running out the fresh water port, so there is a second one way check valve there.
If the inlet port check valve fails, I find water running down the RV side when not connected to a hose but that is not the current problem.

This current problem is the fresh water coming in from the hose overfills the tank!
Two different check valves with two different purpose.

Can we discuss without being disagreeable?

Rossi6998 · 03-25-2024, 11:33 AM

Morich - I don't know the ins and outs, but when this problem happened to me years ago, I found a post online (like this one) which talked about the issue of the water tank improperly filling. The post talked about three possibilities (turn valve to fill tank, check valve at water pump, and check valve at city water hookup). At the time, the easiest for me was replacing the city water hookup. I agree it did not seem logical to me at the time, but it solved my problem.

Morich · 03-25-2024, 12:38 PM

There may be other ways and other things that change the picture. One other thing that can get involved is when we have a valve to give us the option of filling the tank or using fresh water straight in from the hose.
If that valve gets a defect of some special type, the fresh can feed through the opening inside the valve to fill the tank even when set to normal use!

I try not to be too quick to say any one specific idea is correct as there are way too many different designs just in the way we get water into the RV!

Maybe the bottom line take away is to be alert as it may not be what we first think!

About all we can do is look, learn, and try to adapt as we see it at the time!