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Old 06-20-2012, 07:22 PM   #1
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Fresh water pump-Leak?

I've just sourced a pre-pimp filter to help keep the Shurflo pump working.
Should the water pump come on by itself for a few seconds about once an hour? I have a few very small leaks in the system but nothing major.
Does this indicate that the pressure is fallaingThere is a heavy brass pressure regulator next to the pump. What sort of pressure should it be set at. Is it set too high for the system to maintain? Still ironing out the bugs. Raining again and only leaking on my side..
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Old 06-20-2012, 07:26 PM   #2
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Water being incompressible, a slow-drip leak is going to eventually relieve enough pressure for the pump to cycle for a bit to build up to system pressure again. Now, if you were sure you had no drips or leaks that would be a mystery to be solved, but with known leaks it seems reasonable to have the pump cycle for a sec every hour or so as you describe.
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Old 06-24-2012, 11:52 AM   #3
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Had a leak at sink water inlet in my Airstream. Pump would cycle about every minute or so. Solved the leak problem, and pump no longer cycles. Go find that leak, you'll be glad you did when you go to replace flooring and don't see rotted wood sub-floor caused by water leak......
Thanks, Derek
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Old 06-24-2012, 02:46 PM   #4
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Note that if you just filled the system, there's likely air left in the plumbing and water heater you have not yet flushed. This air will slowly dissolve into the water after pressurizing the system, and this can cause the pump to cycle a bit very briefly.

This should of course reduce in frequency and stop after a while. A 6 gallon water heater alone will absorb about 1.5 grams air at 45 psi and 77F. Since air is about .3 lbs/cubic foot, this works out to about 300 ml total dissolved air. Even if the water in the tank was completely saturated with air, the difference in solubility at 45 psi vs 14.7 psi (normal air pressure) means that 200 ml of additional air will dissolve, thus causing the pump to cycle since the pressure will drop.

Air Solubility in Water
Air - Temperature, Pressure and Density

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Old 06-24-2012, 04:04 PM   #5
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Some pumps can also have a very tiny internal leak allowing the water to flow backwards from the pressure side to the suction side. This can drive you nuts, looking for an external leak when none exists. The pump runs, the pressure builds up, the pump shuts off and the water leaks back to the other side of the pump. On one like that I finally found a tiny curl of polyethylene plastic from the tank building and threading process stuck in the check valve internal to the pump. It was so small it even went through the stainless steel filter screen. I removed it, and TA DA, no more pump cycling.

But, the most common thing, as others have said, assuming no external leak, is you need to get some air into your hot water tank to act as a cushon.
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Old 06-25-2012, 07:43 PM   #6
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Rule out a leak...sooner, the better...ours used to cycle on every hour or so, and at night, laying there thinking about it drove me nuts,,,the leak was in the shower, and the fix was relatively simple...once I remembered to TURN OFF THE WATER PUMP!!!
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Old 07-30-2012, 07:39 AM   #7
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Thanks. I could'nt find any leaks in the supply pipes to the taps. I did find that water started dripping from the 'City water' supply hole on the outside of the coach. I thought that the big brass/iron regulator was faulty and was allowing water to flow back to the hole. Has it got an in-built non return/check valve?
Assuming it was faulty I fitted a non return valve in the plastci pipework under the coach between the City water fill hole and RY slowly once but now wont fill thru this hole. It still drips and the water pupmp still keeps coming on. There must be a check valve in the regulator to stop all the water running back out from the pipes/tank thru the City water hole right??
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Old 07-30-2012, 07:45 AM   #8
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It is pretty common to have a little leak back into the tank from the check valve so if you find nothing else this is probably it.
I find it seems to be worse for me when the trailer hasn't been used in a while.

I think minute amount of debri tend to get caught in them at times.
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Old 07-30-2012, 08:03 AM   #9
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If the spring in the check valve is weak. It may seep a little water. If it is leaking at the hose connection point. Just get a plug and install it where the hose connects, with a good washer if course. This also keeps the dirt out when traveling.
As mentioned above, some pumps will have a slight leak and allow the water to flow back to the FW tank.
We always shut the pump off when we don't have a need for water.
When we bought the trailer there was only one pump switch in the galley up front. And with the rear bath it was hard to remember to turn the switch on before heading back to the bath. So I installed a second switch in the bath.
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Old 07-30-2012, 09:02 AM   #10
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Thanks. Yes a second switch is my ideal set up in the bathroom.
I did install a check vlave in the City water inleat but it's either fitted the wrong way round or is a dud. the arrow on it points from the inlet towards the regualtor/pump/tank. This is right isnt it? Water flowing in the direction of the arrow but checked' from flowing/dripping back out the hole right?
The light on the monitor panel for the pump has stopped working now. Is it a normal bulb and how do I get it out. It is/was a bright green colour.

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Old 07-30-2012, 11:15 AM   #11
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I'm not familiar with the light. But it sounds like you have the check valve installed correctly.
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