Tuesday, March 28, 2023


Ask Dave: Good RV water pressure with city connection, none from onboard pump. Why?

Dear Dave, 
About a week into a three-month trip, my Shurflo water pump suddenly stopped providing RV water pressure (barely trickles out, then no water flows). The city water connection/pressure works fine. No water is leaking out of the check valve. There are no water leaks. I have blown air through the water lines between the pump and fresh water tank, and through the water line from the outflow side of the pump. I can manually (with my mouth) suck water from the fresh water tank through the pump’s intake line. The pump strainer has no obstructions. Pump water line connections are tight.

Pentair tech first suggested disassembling and cleaning the interior of the pump. I was in Quebec, Canada, so that wasn’t practical, so I purchased and installed a new (identical) pump. The issue persisted. The tech now thinks there may be a vacuum leak somewhere and suggested checking the water line connections with soapy water, but I can’t do that while traveling since I would have to access the water tank by dropping the trailer’s coroplast cover under the trailer. I will try after I get home (Arizona) after my trip.

No water from tank for two months

I’ve been without access to water from my fresh water tank for over two months. My pump has always worked fine and the only thing different is that just prior to my trip, I installed an Oxygenics Fury shower head. However, that does not appear to be a factor since it works fine using city water connection/pressure.

Any ideas as to what may be causing the loss of water pressure or any additional troubleshooting I can try? Any tips on how to locate a vacuum leak in a water line, and where specifically to look? I’m guessing the issue is the water line and/or connection between the fresh water tank and the pump, but I have never had to deal with an issue like this, so I am shooting in the dark. (Sorry for the long question, but I wanted to give you as much info as possible.) Thanks!! —Greg, 2019 nuCamp T@B 320 S Boondock Lite

Dear Greg,
First, did you verify there is 12-volt power at the pump location and that you can hear the new pump running? Did you bench-test the old pump? I know that would not be easy as you are traveling right now. However, it can be done on a picnic table with jumper cables and a hose to water.

RV water pressure obstructions

If you know the pump is working properly, then it has to be an obstruction either before or after the pump. Check your incoming line to make sure there is no kink in the hose. I would also disconnect the outgoing hose and run the pump to see if it gets any flow, which will help isolate the obstruction at the pump or somewhere downstream. If you do not get any flow, it has to be in the supply line and possibly an obstruction in the fresh water tank. You can disassemble connections to verify flow along the way.

If you do have flow at the pump, it is an obstruction somewhere downstream. Something I have seen is a vacuum valve inline that could be the issue.

This is a photo from a reader that had one of these leaking. However, it could be clogged. It was located under the bathroom sink so it was on the outgoing side of the pump and city water, but I have found them on both sides. This diagram is of a Winnebago Class C and it is on the city water inlet.

If you have connections like the clamp-on style in the above photo, you will have a difficult time getting a water line off other than the screw-on one at the pump itself, which would be very messy. You could disconnect at the pump and hook up a test hose that can be run outside.

Another test for RV water pressure issues

Another option would be to cut the hose after the outgoing side, test it, then use a “Flair It” fitting, which is a compression fitting that can easily be installed and tightened with a pliers or channel lock. This is what Winnebago uses and it can hold pressure in excess of 60 psi. I see Ace Hardware carries them in most locations or you can get them on Amazon.

It’s not in the winterizing position, right?

One last thing. Make sure your rig does not have a winterizing valve or that it’s not in the winterizing position. When this valve is turned, it diverts the water draw from the fresh water tank to the winterizing tube, which is the one in this photo running down to the bottom. It is placed in a gallon of pink RV antifreeze and the water pump draws it up and runs it through the system rather than filling up the fresh water tank with RV antifreeze. If the valve is in the winterizing position and the hose is not in the antifreeze jug, the pump with simply draw air and you will have no water in your plumbing!

 You might also enjoy this from Dave 

What water pressure should I have at the campground?

Dear Dave,
When at a campground, what is the suggested psi setting for an adjustable water pressure regulator? —Tony, 2003 Holiday Rambler Vacationer

Read Dave’s answer

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


We have started a new forum link for Ask Dave. Please be as brief as possible. Attach a photo or two if it might help Dave with his response. Click to visit Dave’s forum. Or send your inquiries to him using the form below.

Click or drag a file to this area to upload.




0 0 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
bill bateman
5 months ago

I’d try your recommendations only doing the ‘winterized’ test 2nd after the power to the pump test.
The ‘winterized’ idea seems the most likely culprit.

Ron Seidl P.E.
5 months ago

There is a small check valve in the Shureflow pump that will get pushed in too far if you overpressure the water line. You can disassemble it and make sure the check valve rubber flapper is not stuck.

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.