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Old 14-05-2013, 13:20   #1
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Where's the leak?

This spring I noticed the pressure pump cycling on after 10 or 15 minutes regardless of whether or not the faucet has been used and pressure drained from the pressurized water system. It will of course cycle on when the faucet is open to pressurize the system and force water out. But since it's cycling on... when water is NOT being used.. it means that the system has a leak... and is losing pressure and the pressure sensitive switch in the Shruflo pump then cycles the pump on to bring up the pressure.

I don't SEE any water leaks and so what's up? Is the pressure sensor messed up? or is there a leak... say at the top of a tank... where the level gauge is connected and that being at the top of the tank is allowing air to leak out draining the pressure... but no water.

Any other thoughts on what might explain this?
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Old 14-05-2013, 13:40   #2
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Re: Where's the leak?

Assuming that the pressure water system is the same as a house (a house with a well) then it could be several things.
First suggestion is turn off your pump and open a tap to drain water pressure to zero. Now near the top of your tank is an air valve, like a tire fill valve. Check the pressure there. This is the captive air bladder pressure. If it is too low or too high it will mess up your pump cycling. It should be a little less than your water pressure is set for. You will have to check the manual for the tank, or research it on the internet to find the optimum setting. Adjust accordingly, then close your tap and turn on the pump.
When the pump switches off, check your water pressure. This is your cut-out pressure. Open a tap a little to allow a slow release of pressure, and watch the pressure guage. When the pump turns on you have found your cut-in pressure. Record the cut-in and cut-out pressures for future reference. If they are very close try adjusting the pump switch so there is a larger gap between them. You may notice water pressure drops before the pump comes back on, but it will cycle less.
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Old 14-05-2013, 13:58   #3
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Re: Where's the leak?

There is an internal check valve in the pump. If this begins to leak, pressure will be released into the unpressurized side of the system and the pump will cycle to raise the pressure back up to where it's supposed to be.
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Old 14-05-2013, 18:07   #4
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Re: Where's the leak?

Faulty pump... I could change it out and see if it stop and then have a spare which is less than perfect (old pump).

Thanks.
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Old 14-05-2013, 18:19   #5
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Re: Where's the leak?

It either leaks back into the tank thru the check valve, as said above. Or into the hull thru a leak in the pressure water plumbing. Back to the tank wastes energy. Into the hull wastes both energy and water. The evidence will be in the bilge after a few hours. Maybe turn off the binge pump for a while or look for dampness in the bilges. On a complex boat it could be leaking in places where it would go overboard, I suppose, like the water maker flush.

It won't be air leaking from the pressure tank because all the air would be lost in a few cycles.

(Or the leak is out a tap, which should be obvious...)
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Old 15-05-2013, 05:21   #6
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Re: Where's the leak?

The bilges are dry... where the tanks are... and there is only a manual bilge pump so no leaking water has been removed by an electric bilge pump.

My understanding is the fresh water pressure system is a closed one... but as we use the water, air is drawn into the tank... ie the use of water is not pulling a vacuum. So there is air above the top of the water in the tank... but pressurized water with the system hoses by the pump which is inline.... and a "pressure accumulator" which I believe has a rubber diaphragm and bladded... which compresses air when the pump cycles on. If you don't have a pressure accumulator as soon as a plumbing faucet is open the pressure drops and the pump cycles on an water flows. If you have a pressure accumulator the bladder provides some pressure...and when it the volumne of water equal to the bladder volume is used... then the pump cycles on and pushes diaphragm and compresses the air inside the bladder.

My pump comes on when the valves are open. So the pressure accumulator is not working (air leak) and can't compress any air. So my system is like one without a pressure accumulator.

But why is is the pump cycling on? What is causing the pressure inside the closed system to drop when all valves are closed? Where is the leak? I see no water so assume it's air or as previously mentioned a faulty pump. Perhaps at one of the tap valves?
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Old 15-05-2013, 05:31   #7
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Re: Where's the leak?

If there is no pressure tank it doesn't take much water loss to depressurize the system. The leak could be so small that you would never find it.

If you do have a pressure tank and the pump comes on every 15 minutes you ahve a leak and/or the pressure is going back though the pump into the tanks. If you don't seem to be losing water the problem is probably in the pump. Either replace the pump or put a check valve on the discharge of it.
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Old 15-05-2013, 05:33   #8
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Re: Where's the leak?

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Originally Posted by defjef View Post
The bilges are dry... where the tanks are... and there is only a manual bilge pump so no leaking water has been removed by an electric bilge pump.

My understanding is the fresh water pressure system is a closed one... but as we use the water, air is drawn into the tank... ie the use of water is not pulling a vacuum. So there is air above the top of the water in the tank... but pressurized water with the system hoses by the pump which is inline.... and a "pressure accumulator" which I believe has a rubber diaphragm and bladded... which compresses air when the pump cycles on. If you don't have a pressure accumulator as soon as a plumbing faucet is open the pressure drops and the pump cycles on an water flows. If you have a pressure accumulator the bladder provides some pressure...and when it the volumne of water equal to the bladder volume is used... then the pump cycles on and pushes diaphragm and compresses the air inside the bladder.

My pump comes on when the valves are open. So the pressure accumulator is not working (air leak) and can't compress any air. So my system is like one without a pressure accumulator.
You might very well be getting a pressure leak back through the pump. When it pumps up to pressure, if there is a check valve in the pump (probably is) and it is not tight, the the water will leak back through the pump. At some point the pressure falls below the pressure switch level (which will be set at higher than -0- psi, since you have an accumulator fitted, albeit it is defect), the pump starts up again.

The solution is to either rebuild the pump (or at least the check valve) and while you are at it, replace or rebuild the accumulator.

PITA, but not very difficult and cures the problem.
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Old 15-05-2013, 07:05   #9
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Re: Where's the leak?

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.............. if there is a check valve in the pump (probably is) and it is not tight, the the water will leak back through the pump. .............
I posted that above, but there has to be a check valve in the pump or in the intake line right before the pump. Think about it - You can't have pressure on one side of the pump and not on the other side without a valve to close off the pressurized side from the non pressurized side.

The lazy man's fix for this is to leave the pump as is and install an external check valve in the line as close as possible to the pump inlet.

The proper fix is to repair or replace the pump. Comparing the cost of the replacement pump to the cost and effort to repair, my choice is to simply replace the pump. If it's an expensive pump, it might pay to repair it. Mine was just a little over $100 and a repair kit is about half that.
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Old 15-05-2013, 07:15   #10
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pirate Re: Where's the leak?

I'll vote for checking the pressure in the tank and resetting before anything else... had similar happen after running out of water a couple of times... water levels in there got so low the pump started running constantly after a while... let out a load of air and all was well again.
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Old 15-05-2013, 07:38   #11
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Re: Where's the leak?

mine cycles occasionally so i leave it turned off until i need water then i turn it on again..isnt a big deal, and i save electricity. and water....
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Old 15-05-2013, 08:04   #12
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Re: Where's the leak?

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mine cycles occasionally so i leave it turned off until i need water then i turn it on again..isnt a big deal, and i save electricity. and water....
You have a problem and it's unlikely that it will fix itself. You have a choice of fixing it on your terms (at home with tools and parts available) or on its terms (anchored out for a week with no potable water available and no tools or replacement parts).

BTW: You're not saving anything. A properly working water system uses no electricity or water until you call for it.
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Old 15-05-2013, 08:22   #13
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Re: Where's the leak?

only uses electricity when pump cycles....lol

mine has been this way for over 5 yrs--since before i bought this boat--it isnt gonna kill ye to have pump cycle, but do turn it off at breaker ... then it wont cycle.


btw--i have 2 spares and this is the quiet shurflow silent pump--will rebuild when it dies, but until then, it is fine.
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Old 15-05-2013, 16:59   #14
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Re: Where's the leak?

It's no biggie to turn on the pump circuit when one needs water pressure and off when one is done. It's the latter I forget only to be reminded when the pump cycles on.

Thanks to everyone for the comments. I think it's the pump and it's not very expensive to replace.
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Old 15-05-2013, 18:33   #15
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Re: Where's the leak?

It doesn't take much of a leak to make the water pump cycle. I take it you do not have an accumulator tank. Just a few drops will make it cycle. I would check for leaks again, especially at the hot water tank.
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