Why is My RVs Freshwater Tank Filling When Connected to City Water?
When you hook up your RV to water via the city water connection, a check valve inside the water pump is supposed to cut off the fresh water tank so the city water connection doesn’t fill it.
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City water filling your RV fresh water tank is bad because once the tank is full pressure starts to build up inside the tank and pipes connected to it.
Water will also start leaking out wherever it can, that’s usually around the freshwater fill hatch and out the air vent.
Since the freshwater fill has a cap on it the water can start leaking from the inside of the freshwater fill because of the pressure building up.
It’s not only a waste of water, but it’s also a potential leak issue.
If you connect your RV to water and the freshwater tank starts to fill from the city water connection there’s probably something wrong with the check valve/back flow preventer.
In this post, I’ll talk about how you can try and fix the check valve and also some good replacements if the fix doesn’t work.
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City Water Filling Freshwater Tank Quick Fix
Here’s a quick fix you can try if the city water is filling your RV fresh water tank.
- Turn off the city water.
- Turn on the RV water pump.
- Open a faucet so the RV water pump starts to pump water from the fresh water tank.
- You want the pump to run to try and clear out whatever is blocking the check valve inside of it or to reset it.
- Let the pump run for a few minutes.
- Turn off the faucet so the pump stops.
- Repeat steps 3-5 a few times. Using hot water is also a good idea.
- After flushing out the RV water pump close the faucet and turn off the pump.
- Turn on the city water again slowly.
- If the pressure from the water source is high it could be the reason the check valve isn’t engaging. Make sure the water pressure isn’t above 60 psi and open the hydrant slowly so the valve can work properly.
- Hopefully, a little reset was all the check valve needed and your city water connection isn’t filling the fresh water tank anymore.
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What to Do If the Check Valve Inside the RV Water Pump Still Won’t Work
If you’ve tried the quick fix above a few times and the water tank is still being filled by the city water connection you have two options.
Replace the RV water pump, or add an external check valve.
RV water pumps can be pretty spendy, and if it’s working great otherwise I recommend just adding a check valve by it instead of replacing the whole thing.
Some RVers add check valves anyways as an added precaution. It’s an easy install that most people can do on their own.
How to Install a Check Valve Next to an RV Water Pump
Parts Needed
- Inline Check Valve (click to view on Amazon)
- Needs to have 1/2 inch NPT threads to work with most RV water pumps.
- Plumber’s Tape (click to view on Amazon)
Where to Install the Inline Check Valve
Every check valve should have an arrow or some sort of marking on it to indicate what direction the water will flow from the valve.
You want the water to be able to flow from the fresh water tank, through the water pump, then into the rest of the RV.
The best place to install a check valve is in between the RV water pump and the inline pump filter. It’s usually on the side that’s connected to the fresh water tank.
The reason you should install the check valve after the filter is to help keep it clean so nothing can block it.
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How to Install an RV Check Valve
The installation part is easy. All of the threads and connectors you need are already built into the RV water system.
The Camco Check Valve (click to view on Amazon) has the male end on the water input side and the female end on the water output side.
Unscrew the inline filter from the RV water pump and the pipe connecting it to the fresh water tank.
If your water pump doesn’t have a filter near it you should consider installing one.
It’s a simple part but it can save your RV water pump if things like dirt, rocks, or bugs get into your RV fresh water tank.
Screw the male end of the check valve into the female end of the inline filter. Use some plumbers tape to make sure the threads are watertight.
You shouldn’t need any tools to remove or put on any of the connections. They are meant to be hand tightened only.
Next, add some plumber’s tape to the threads on the RV water pump and screw on the check valve and the water filter.
The water filter and check valve will move as one part now since they are fully connected.
After that connection is secure you can reattach the pipe from the freshwater tank to the end of the filter.
The new check valve should stop any water from entering the RV fresh water tank but still allow water to flow from the freshwater tank when the RV pump is on.
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Other Places With Check Valves In an RV
You can also find a check valve directly behind the city water connection.
This is what stops water from leaking out when the RV water pump is on and you aren’t connected to city water.
There should also be a check valve by the hot water output on the water heater. This stops water from flowing back into the tank.
There might also be one on the water input side of the water heater to stop hot water from flowing out of the input.
Have any more questions about the city water filling the freshwater tank issue or check valves? Leave a comment below.
I have just purchased a very used camper to turn into my first home. My dad who is 78 years old. Tried to help me get water into my camper from a city water spigot. There is no electricity in my camper so dad cut and capped off the waterlines going to the water pump. When I hooked up the water hose to the camper, water started going into the camper through the faucets very slowly. Then all of a sudden, the white water tank underneath the camper started overflowing everywhere. Can you please help me because I have no idea what I am doing. I am 54 years old and trying to do this by myself. I would really appreciate any advice you could give me. Thank you very much.
Hi Genice,
The water tank is probably filling because the water pump was bypassed, but the inner RV water pipes are still connected to the freshwater tank somehow.
If you find the pipes that are connected to the water tank and cap those it shouldn’t fill with water anymore.