Fresh Water Tank Overflow

[droark55]

I have a 2018 Thor ACE 30.4.

This happens occasionally when my fresh water tank is filled half way. So, I’m hooked up at a RV site and the next morning I noticed my fresh water tank is full and overflowing.

What is causing this happen? Is it an easy fix? Is there a video to help with the repair? I’m not very experienced on RV repairs. Or is it best to have an experience RV mechanic you repair it?

Thank you for your help!

Danny

[OldWEB]

Typically the problem is a check valve, with all the different setups, here are a few suggestions on where to look. Good luck

[paulwadley]

A typical issue with the Anderson water valve. That is the valve you set to fill your tank or run the city water line into your rig. The valve has multiple rubber "O" rings that sometimes get twisted or torn which allows city water to flow through your system and into your fresh water tank at the same time. You can buy a new Anderson valve and replace it if needed for around $35.00. It is an easy fix. Make sure you do not turn on the city water to your hose until after you have selected where you want the water to go (Tank or rig water lines). That is sometimes an issue if it is pressured at the time you try moving the water valve that causes the rubber o rings to tear.

[bevedfelker]

Had this happen several times in my 2015 Vegas. Don't know which water pump you have, but in my case it's the check valve that is internal to the pump. It's a simple thing to remediate (not interested in spending money on a new pump if I can correct the problem easily).

For what ever reason (probably city water pressure) the water pressure is forcing the check valve in the pump to open slightly allowing water to flow from city water lines, through the pump, and then back filling the fresh water tank.

What I do is turn off the city water and run the pump for about a minute using the faucet in the kitchen sink. Turn the water off, turn the pump off, and then reopen the city water. I then use the low point drain to drain the water from the fresh water tank.

This isn't a permanent fix, but I've only had the tank fill and overflow 3 times in the past 5 years of using the RV.

[cavie]

Originally Posted by bevedfelker

Had this happen several times in my 2015 Vegas. Don't know which water pump you have, but in my case it's the check valve that is internal to the pump. It's a simple thing to remediate (not interested in spending money on a new pump if I can correct the problem easily).

For what ever reason (probably city water pressure) the water pressure is forcing the check valve in the pump to open slightly allowing water to flow from city water lines, through the pump, and then back filling the fresh water tank.

What I do is turn off the city water and run the pump for about a minute using the faucet in the kitchen sink. Turn the water off, turn the pump off, and then reopen the city water. I then use the low point drain to drain the water from the fresh water tank.

This isn't a permanent fix, but I've only had the tank fill and overflow 3 times in the past 5 years of using the RV.

Low point drain will not drain the FW tank. The FW tank has it's own drain. Low point drains drain the piping system hence the name. They are are 1 hot and 1 cold.

[Yvonnemarc]

Just so you know the ACE 30.4 doesn’t have an Anderson valve. So eliminate that quick. It’s a bad check valve on the pump. There is an isolation valve between the FW tank and the pump. Close it and the city water won’t back feed into the FW tank. I know that doesn’t solve the check valve issue but your tank won’t fill up and overflow. Check valves in pumps this small aren’t usually external so you’ll need to get a new pump.

[Lt Keefer]

Same things has happened a couple of times in my Hurricane. My fix is turn off the city water. Use the FW tank for a while, Then switch back to city water. I figure the check valve in my pump gets some 'junk' that keeps it open a tad allowing water to flow back to the tank. It hasn't happened lately, but I added cleaning the 'filter' by the pump to my routine maintenance list.

[cavie]

Originally Posted by Yvonnemarc

Just so you know the ACE 30.4 doesn’t have an Anderson valve. So eliminate that quick. It’s a bad check valve on the pump. There is an isolation valve between the FW tank and the pump. Close it and the city water won’t back feed into the FW tank. I know that doesn’t solve the check valve issue but your tank won’t fill up and overflow. Check valves in pumps this small aren’t usually external so you’ll need to get a new pump.
Attachment 23396

Water pumps are very much rebuild able and easy to do.

When on city water turn the pump off.

[droark55]

I want to thank everyone for your quick response and suggestions.

Do I follow the city water intake line to find the water pump?

Originally Posted by droark55

I have a 2018 Thor ACE 30.4.

This happens occasionally when my fresh water tank is filled half way. So, I’m hooked up at a RV site and the next morning I noticed my fresh water tank is full and overflowing.

What is causing this happen? Is it an easy fix? Is there a video to help with the repair? I’m not very experienced on RV repairs. Or is it best to have an experience RV mechanic you repair it?

Thank you for your help!

Danny

[cavie]

Originally Posted by droark55

I want to thank everyone for your quick response and suggestions.

Do I follow the city water intake line to find the water pump?

No. You turn the pump on. Open a faucet. Walk around and listen for the pump.
Take a #2 square driver with you to remove a panel hiding the pump. Look under bed, drawers etc.

[abjbrtd]

We've had this happen 2 or 3 times in the past couple of decades.
Always try the easy fix first.

Turn the campground water off.
If your pump is on turn it off.
If it's off, turn it on then off, a couple of times.
Turn the city water back on, check the overflow.

So far with this method we've never had to replace the check valve.

[Yvonnemarc]

Originally Posted by cavie

Water pumps are very much rebuild able and easy to do.

When on city water turn the pump off.

Very easy but not if you’re a noob. They’re throw-aways.

[cavie]

Originally Posted by Yvonnemarc

Very easy but not if you’re a noob. They’re throw-aways.

go to Youtube, Watch a few videos and you won't be a noob very long.