on 'city' water but fresh water tank keeps filling

Nore · October 6, 2018

simply stated, the problem is:
On 'city' water but for some odd reason the fresh water tank keeps filling
How can I alleviate that?

Been ongoing since last Sunday - i accidental flipped the pump switch on while cleaning. It was only on for 2 sec, but it seems like that may have started the problem. Everything was peachy prior to that (been at this RV Park close to a yr. - always on 'city' water)

Seems like I have tried just about everything logical, to no avail. I've been scouring posts for help and yesterday the park mgr and I took out the SHURflo 4008 & very gently cleaned it. It looked new!! Put everything back and turned on the city water again in hopes it would handle the sucking. Took a couple of hours before I was able to see (on the tank gauge) that the Fresh tank was at 1/3.

Anyone have any ideas?? 😭

Dutch_12078 · October 6, 2018

If you have a tank fill valve in your wet bay, check that it hasn't been partially opened. There's a check valve in the pump that's supposed to prevent back filling into the fresh tank. It only takes a small spec of dirt or mineral deposit to block it partially open. Sometimes running the pump for awhile will clean it out. Another option is to add an external check valve in the pump line on one side of the pump.

mptjelgin · October 6, 2018

Agree that this is typical of the check valve on your water pump not closing completely, especially since it started after you accidentally ran the pump.

A tiny bit of dirt or perhaps a little curl of pipe material left over from installation has probably gotten caught in the check valve. As noted above, running the pump for a bit may flush it out. I'd switch over to the pump and turn the water on and off a few times to pulse water through the valve. Hopefully that will dislodge whatever is causing your problem.

When you took the pump out and gently cleaned it did you remove the head, check the diagrams, etc.?

GeorgiaHybrid · October 6, 2018

If you have an Anderson 4 way valve, try replacing the Orings on the valve or buy the replacement valve insert. It takes about 5 minutes to replace or repair one. Those are standard on late model DRV"s and probably several other trailers. When the Orings get worn or cut, the fresh water tanks will fill.

Nore · October 6, 2018

Thanks for the reply Dutch! I really wish I did have a switch or lever that controlled that - but I don't in this TT.

Now, I did run the pump, Tuesday I think, I thought I'd try reverse psychology on the thing. I took city water hose off completely & ran water in sinks with the pump for a while. However, I haven't tried that since we cleaned the pump. Might try it again.

Adding an external check valve might be a possibility - however, space is at a premium in the itsy space it's crammed into - Will add to list of possibilities!!

Thanks again for your help!

Dutch_12078 · October 6, 2018

Wishing you good luck with it!

Nore · October 6, 2018

TO mptjelgin

Did the flush number - but might try that again as mentioned above.

Yup - had all the diagrams!! Checked & re-checked throughout the process - removed the upper body, then valve assembly and drive assembly -cleaned everybody & checked the diagrams to ensure it was back they way it should go (I'm pretty anal)

TO GeorgiaHybrid

It is a Pentair SHURflo - but I did check all O rings and fittings - Honestly, it looks brand new

Thank you both for your replies!!!!

Lance A Lott · October 6, 2018

Take out the pump and put in a ball valve, for now. The water is going through the pump some how. The ball valve will keep you from having a flood. If you have room you can use it instead of a check valve.

57becky · October 6, 2018

I had the same problem several years ago, and installed an inline check valve on the tank side of the pump. Solved the problem....but, I replaced the pump some time back, and just recently I developed a water leak. Turns out, the old pump did not have a screen on the tank side, but the new one does. I guess after a while, the fitting on the screen started leaking from the new pump's failed internal check valve and the screen device's fitting could not handle the pressure and the check valve was holding water from returning to the tank. The fix was to cut out the previously installed check valve on the tank side of the pump and install a new one on the pressure side of the pump. I haven't had a leak since. All this to say, install the check valve on the pressure side of the pump to avoid problems. In the photo, the check valve is the brass thing in the blue line. The two white couplings in the line to the left and behind the brass check valve is where the original check valve was installed.

Kirk W · October 6, 2018

10 hours ago, Nore said:

It is a Pentair SHURflo - but I did check all O rings and fittings -

Most of the ShurFlo pumps don't have an actual check valve but are a diaphragm pump that acts as a check valve when operating properly. Did you use the rebuild kit from ShurFlo? Most of them have a new diaphragm as well as the o rings, or at least they used to. I haven't worked on one for several years now but always did the entire kit back when I did. In my experience, leak back has been the most common failure of those diaphragm pumps.

How old is the pump you have now?