Ball valve to prevent city water backflow thru pump to fresh water tank

[Air Team]

My wife and I have a 2016 Airstream Flying Cloud 26U. While we never fill or use the fresh water (FW) tank, it does get some water resulting in a small drip near the FW tank drain petcock. I suspect city water backflow through the pump and into the tank is the cause. A reasonable fix would seem to install a ball valve in the water system to prevent the backflow. I consider a check valve a somewhat less reliable choice and the ball valve should be the better choice since we never/rarely use the FW tank. Listed below are a few concerns related to this matter. I will appreciate any feedback on these issues.

Q1. Where is the better location for the ball valve, either between the pump and FW tank, on the suction/intake side of the pump or between the pump and city water input on the pressure/discharge side of the pump? While researching this issue, I have seen both locations noted as preferred by readers. Confusing - maybe it doesn’t matter?

Q2. Why would one position, on one side or other of the pump, be better than the other? Again, maybe it doesn’t matter.

Q3. Is there one type of ball valve that would be the best choice - SnakeBite, crimp connection, brass/stainless, plastic, etc?

Maybe I am overthinking this project, but these are real and valid questions in my mind. Thank all of you that respond with assistance in this matter. It will be appreciated.

[Wazbro]

Q1 I would put it on the discharge side, may not matter much.
Q2 On the discharge side the pump should build pressure and shut off, on the input side it may continue to run.
Q3 I would get a PEX valve to put in.

[Malia20]

I had a pump fail so I installed a ball valve on the discharge side of the pump. My theory was a valve on the suction side of the pump does not stop city water pressure from pushing against the one-way valves on the pump ( and the pump form leaking until pressure is balance with the suction-side valve. It was those pump valves that failed on my pump. A valve on the discharge side also allows me to remove/work on the pump while trailer is functioning on city water pressure.
I used a 90 degree turn ball valve installed with pex crimps.
Fred

[Mollysdad]

Ball valve or check valve?
Are we using the terms interchangeably? To me a ball valve has a lever to turn the ball 90º and stop the flow. A check valve allows water one way but not the other. Installing a ball valve on the discharge side of the pump would stop water everywhere, no?

On the 26' the pump is under the closet floor with access from the front if you lay on the floor. I've seen people install a check valve so you don't need to get access when connecting city water.
I'm actually considering cutting a hole in the closet floor and covering it with an aluminum plate so I can access stuff from above. (Big enough for my hand and a screwdriver.)
I just replaced my pump because it also leaked internally, and my fresh tank filled also. Then I bought the diaphragm kit so the old pump can be the replacement if needed.
The real culprit is not keeping crud out of the fresh tank, so the buildup on the flapper valves in the pump get jammed. Some bleach periodically and a good filter on the hose when filling the tank. Then empty the tank periodically <gasp>. I pled guilty until now.

From the "I wish I knew this" file. IF you replace the pump, connect the water lines before screwing the pump down. Why? I did the opposite and all the gyrations to get the threads started caused a big leak in the PEX farther up the line.
I used the theory, "There's no problem so big you can't make it worse."

[Malia20]

Originally Posted by Mollysdad

Installing a ball valve on the discharge side of the pump would stop water everywhere, no?

A ball valve (not check valve) on the discharge side of the pump but before any other fixture/"T" on the discharge (house) side of pump will isolate the pump from the house plumbing including the city water input (pressure). This protects the pump from the city water pressure. Yes I know there is a pressure reducer gizmo (plastic) in the city water inlet, but as others have reported and I have experienced that gizmo can also fail or not reduce the pressure enough. I feel that occasional high pressure can be detrimental to the pump. And I know from experience, you only lose a pump when it is most inconvenient.
Fred

[ROBERT CROSS]

When we have, not often, hooked up to our water supply at home, [60+psi.]
The pump is bypassed and never runs.
Are newer models different?

How would putting a valve there help?

Bob

[richard5933]

Originally Posted by ROBERT CROSS

When we have, not often, hooked up to our water supply at home, [60+psi.]
The pump is bypassed and never runs.
Are newer models different?

How would putting a valve there help?

Bob

The pump isn't actually bypassed when you connect city water to the outside inlet. Rather, the pressure from the city water system is pushed against the outlet side of the pump causing it to think that there's already enough pressure and keeping it from turning on.

For times when the city water pressure is low, it's possible to use both the city water inlet AND the on-board pump to increase pressure.

My vote is for a check valve (not a ball valve) on the discharge side of the pump. It will prevent city water from backing up into the freshwater tank and still allow the pump to function properly.

You may not have any plans to use the on-board pump right now, but plans change. Plus, one day you'll sell your trailer and having a ball valve in the pump's plumbing will thoroughly confuse the buyer who isn't expecting that.

Yes, check valves fail. But so do ball valves. Might as well install the correct part. If it's a quality-made check valve it should last as long as a ball valve.

The check valve that comes inside the pump is tiny and plastic, but you can install a larger brass/stainless check valve yourself on the discharge side of the pump.

[ROBERT CROSS]

Originally Posted by Air Team

My wife and I have a 2016 Airstream Flying Cloud 26U. While we never fill or use the fresh water (FW) tank, it does get some water resulting in a small drip near the FW tank drain petcock. I suspect city water backflow through the pump and into the tank is the cause. A reasonable fix would seem to install a ball valve in the water system to prevent the backflow. I consider a check valve a somewhat less reliable choice and the ball valve should be the better choice since we never/rarely use the FW tank. Listed below are a few concerns related to this matter. I will appreciate any feedback on these issues.

Q1. Where is the better location for the ball valve, either between the pump and FW tank, on the suction/intake side of the pump or between the pump and city water input on the pressure/discharge side of the pump? While researching this issue, I have seen both locations noted as preferred by readers. Confusing - maybe it doesn’t matter?

Q2. Why would one position, on one side or other of the pump, be better than the other? Again, maybe it doesn’t matter.

Q3. Is there one type of ball valve that would be the best choice - SnakeBite, crimp connection, brass/stainless, plastic, etc?

Maybe I am overthinking this project, but these are real and valid questions in my mind. Thank all of you who responded with assistance in this matter. It will be appreciated.

The ball valve will work very well in the leaky FW drain.

Bob
🇺🇸

[Mollysdad]

Originally Posted by Malia20

A ball valve (not check valve) on the discharge side of the pump but before any other fixture/"T" on the discharge (house) side of pump will isolate the pump from the house plumbing including the city water input (pressure). This protects the pump from the city water pressure.

I agree. My point was when installing a ball valve, every time you go from city water to tank water, you'll have to operate the ball. In my case that's not practical.

[richard5933]

Originally Posted by ROBERT CROSS

The ball valve will work very well in the leaky FW drain.

Bob
🇺🇸

Agree that in the case of draining the freshwater tank a ball valve is a good option. The valves that come from the factory are not suitable for the task.

[ROBERT CROSS]

An added point...notice that in the picture, the street side was lifted while draining. That was not on purpose.
About three gallons came out.
I now lift for every Winterization..BSTS.

Bob
🇺🇸