One day when we were camping, we discovered water was dripping from the freshwater tank’s overflow outlet.

We had city water at the campground and hadn’t used the freshwater tank in a few weeks, so it didn’t make sense.

Why then did my freshwater tank suddenly fill to the brim?

What’s Going On?

It turns out that this happens rather often.

Inside the water pump is a one-way check-valve that often becomes dislodged and becomes jammed open.

In such a scenario, water from the municipal water connection may flow in the opposite direction via the pump and into the freshwater tank.

Potential Causes

The two main reasons of this are:

  1. Having both the pump running and the municipal water connected at the same time
  2. Having very high water pressure from municipal water without a water pressure regulator
  3. Alternatively, a classic pump failure

Possible Solutions

The most straightforward solution is often to alternate between using the water pump and municipal water a few times:

  1. Offset the camp site water
  2. Fire up the water pump
  3. 10-15 seconds of faucet timer operation
  4. Offset the water pump
  5. Activate the campsite water
  6. 10-15 seconds of faucet timer operation
  7. Three or more times.

This is often sufficient to reset the check-valve within the water pump.

There are many ways to resolve it if it occurs frequently:

  1. Look for a water pump “rebuild kit” and determine if the internal check valve is a functional component.
  2. On the pump’s input side, add your own 1-way check valve to the water line.
  3. Complete the replacement of the pump itself. For choices, see the RV Water Filter Store or Amazon.

The customer service at RV Water Filter Store is excellent if you’re unsure of what you need.

The site’s proprietor once contacted me on a Sunday night to assist me in determining what I required.


There you have it.

If you are linked up to city water while camping and find water gushing out of the freshwater tank’s vent, it’s quite probable that water is backflowing via the water pump.

As you can see, the solutions are rather simple.

RV Water Pump Check Valve Videos Suggestions From Youtube

Step by Step RV Water Pump and Check Valve Replacement – Kevin and Kim Outdoor Adventures
RV Shurflow Water Pump Check Valve Failure – Problem Resolved with 2 Modification Solutions Part #2 – Michael Bracewell The Travel Trailer Guy
RV Water Pump Replacement! Check Valve Problem Solved! – RVBlogger
RV How To – Water Pump Check Valve Bypass – RV fresh water tank for beginners – How To RV

Updated on

Written by Bob Matsuoka
Bob Matsuoka is a blogger and founder of RVing Beginner blog. He has been blogging for over five years, writing about his own family’s RV adventures, tips for people who are interested in buying an RV or taking their family on an adventure by RV.