Seeking Trick to Finding Air leak in Water Line? - Fiberglass RV
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Old 08-22-2019, 06:16 PM   #1
Junior Member
Name: Kirby and Rhea
Trailer: Bonair Oxygen
Nova Scotia
Posts: 13
Seeking Trick to Finding Air leak in Water Line?

We have a 2002 Bonair Oxygen, affectionately known as Eggbert, (since May 2004.) Our habit had been to use the on/off switch to decide when we would run the pump. The water pump can be loud. We have always had lots of pressure in between.
This season we only had cold water while the pump was running. The hot water seems to hold its pressure in between using the pump.
As there are no visible leaks, I was advised to replace the 17 year old pump. I did that but the same problem continues.
(It's worth noting that the old pump would build up pressure and shut off. The new pump only shuts off with the switch)
Do we have an air leak? How do we find it and repair it?
All ideas welcome.
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Old 08-22-2019, 06:39 PM   #2
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Name: John
Trailer: Black Series HQ19
Smith Valley, Nevada
Posts: 2,387
Several things going on here.

You got bad advice on replacing the pump. If the pump fails, it affects both hot and cold, unless it is the internal check valve and there is a separate check valve on the hot side.

With a loss of pressure only on the cold side, it sounds like you have a check valve on the hot side and a slow leak on the cold side. A dripping faucet, toilet valve leak, or a cracked fitting somewhere. And since it still does that with the new pump, it's not the pump check valve that I mentioned.

Does the new pump have a pressure switch? Is it wired correctly? Is it designed to run all the time or come up to pressure and shut off? Not enough info to accurately diagnose.

I don't know why you might think it is an "air" leak. Correctly operating pressure pumps will run all the time if they are air locked, but if you are getting good water flow at the faucets, this is not the problem.

The typical symptom of a leak somewhere is that the pump will run occasionally even if no water has been used. This can be the check valve in the pump that is allowing water to go backward through the pump toward the tank and losing pressure until the pump fires up again, but since you had the same symptom after the new one was installed, that is not the problem.

Figure out why the pump won't shut off. Look for evidence of a very slow leak in the cold water piping.
I only exaggerate enough to compensate for being taken with a grain of salt.
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Old 08-23-2019, 07:21 AM   #3
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Name: JD
Trailer: Scamp 16 Modified (BIGLY)
Posts: 2,144
If there is a check valve on the hot side and it holds pressure and the cold side does not then It could very well indicate that there is a leak through the water pump back into the water tank and not an air leak.
An air leak would pretty soon become a water leak.
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Old 08-23-2019, 08:07 AM   #4
Senior Member
Name: Fredrick
Trailer: Escape 21C
Posts: 318
water line leak

WE found water under the back center "seat" of our Casita Independence once last Spring..about a half pint it was. Turns out we found a slightly loose screw on a clamp on the feed line INTO the pump [from the tank]. {Pump is in Driver side rear corner under a bunk.} Water tank is on passenger-side rear corner..also under a bunk. Tightened that screw clamp and watched the area for a day(kept the cushions and hatches off all day and no more water. Just a thought..check all clamp fittings...
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Old 08-23-2019, 11:07 AM   #5
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Name: Michael
Trailer: Escape
Posts: 2
You probably already checked this, but if you have a hot water heater bypass system for winterizing I would make sure the valves are in the right position to draw from the hot water tank.
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