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Old 11-14-2012, 12:35 AM   #1
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Water Pump pulses for 1/2 sec every 90 seconds

Hello Everyone, quick question...

My 12v water pump seems to pulse "on" for a 1/2 second and does this @ every 90 seconds. I have looked everywhere that I can physically see where the grey PVC water lines run and I CANNOT see any leaks anywhere.

Is it possibly normal (or a sign that the pump is coming due for replacement) that it comes "on" ever so briefly every 1-2 minutes?

I have a houseboat and I could swear that the water pump on the boat never pulses unless I open a tap/faucet.

The pump works fine when I open a faucet etc... But when I close all the taps and faucets etc... It just does a very small pulse (the time it takes to snap your fingers) , so I don't know if this normal behavior as it is trying to maintain 45 lbs of pressure...?

Anybody else notice their 12v water pump do the same thing?

IAN...
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Old 11-14-2012, 03:03 AM   #2
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Pump inlet valves aren't sealing tight so pressure slowly leaks back into the water tank. When pressure drops, pressure switch actuates long enough for the pump to pressurise the pump chamber and the pressure switch switches the pump off - just a fraction of a second.
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Old 11-14-2012, 04:34 AM   #3
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X2 for inlet valves, or you have a very small leak in the ice maker line or some other slight drip. It only will pulse if the pressure drops.

Good luck.
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Old 11-14-2012, 07:09 AM   #4
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Quote:
Originally Posted by Tony Lee View Post
Pump inlet valves aren't sealing tight so pressure slowly leaks back into the water tank. When pressure drops, pressure switch actuates long enough for the pump to pressurise the pump chamber and the pressure switch switches the pump off - just a fraction of a second.
I have the same issue as the OP, it drives me crazy because I've looked EVERYWHERE for a leak. Tony Lee's explanation makes sense. I assume there are rebuild kits available?
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Old 11-14-2012, 08:16 AM   #5
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It could also be the city water fill valve. Do you see any water at all leaking from where you connect the city water hose? Another place to check out would be the hot water pressure relief valve.
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Old 11-14-2012, 08:22 AM   #6
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So it looks like it could be the "inlet valves". I was worried and asking as I thought it could be that it is leaking water ever so lightly somewhere.

The noise doesn't really bother me, but the thought of it pulsing because it is leaking water somewhere (ever so lightly) bothers me.

We all know that a small leak somewhere, over the years creates a real mess.

I just didn't know if a water pump "pulses" if it only means it has to be leaking water OR that there was another explanation?

IAN...

PS: especially since it only "pulses on" for a fraction of a second.
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Old 11-14-2012, 08:34 AM   #7
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I just didn't know if a water pump "pulses" if it only means it has to be leaking water OR that there was another explanation?
There is a pressure sensor inside the pump that shuts the pump off and turns it on as needed to maintain the water pressure. That sensor could be weak and causing problems. But like you, I would look and look for a small leak. As you stated they can cause so much heartache down the road.
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Old 11-14-2012, 08:35 AM   #8
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FWIW, I had this problem on our Bounder. It turned out to be the bypass valve that allows city water into the fresh water tank not being fully closed. No leaks, just water being bled back into the tank.
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Old 11-14-2012, 08:36 AM   #9
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It could also be the city water fill valve. Do you see any water at all leaking from where you connect the city water hose? Another place to check out would be the hot water pressure relief valve.
Good point, I will have to check the city water connection AND the hot water pressure relief valve to see if there is a small drip...
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Old 11-14-2012, 04:41 PM   #10
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Yes, there are pump head rebuild kits including new pressure switch membranes etc.. once in a great while they leak back internally, but usually it is a slow leak as described already.
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Old 11-14-2012, 05:35 PM   #11
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So since there are areas in the RV that I can't see or reach to physically see if there's a small water leak, is there any other way to troubleshoot this issue?

Yopu all know that its physically to see or identify a tiny water leak in the Pex PVC lines.

I wonder if I disconnected the "outlet" from the 12v pump, and put on a separate piece of hose and "plugged it", wouldn't this tell me if it's a leak in the water lines in the RV, or simply an internal leak within the water pump?

I have a small piece of clear hose with the plastic connector that fits on the pump. ( I use this to run antifreeze through the system)

I wonder if it can hold 45 lbs of pressure... hmmmmm...
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Old 11-15-2012, 09:49 AM   #12
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I wonder if I disconnected the "outlet" from the 12v pump, and put on a separate piece of hose and "plugged it", wouldn't this tell me if it's a leak in the water lines in the RV, or simply an internal leak within the water pump?

For sure good idea, if you could put a shut off valve at the end of the hose you could get the air out, eliminating any pulsing caused by air entrapment. This would remove the house plumbing on the pressure side of the pump from the equation, certainly a good start in the process.
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Old 11-15-2012, 04:27 PM   #13
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Quote:
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I wonder if I disconnected the "outlet" from the 12v pump, and put on a separate piece of hose and "plugged it", wouldn't this tell me if it's a leak in the water lines in the RV, or simply an internal leak within the water pump?

For sure good idea, if you could put a shut off valve at the end of the hose you could get the air out, eliminating any pulsing caused by air entrapment. This would remove the house plumbing on the pressure side of the pump from the equation, certainly a good start in the process.
I will see if that clear hose will hold the pressure from the pump, and it should tell me if the pulsing is coming from within the water pump OR from a small leak with the RV plumbing,

Now, if I could just lose half my body weight and become flexible enough to reach the pump, I would be all set

IAN...
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Old 11-15-2012, 05:40 PM   #14
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You DO want to find and fix the problem, even if you think its just he inlet valve. Starting so often will eventually kill the pump..
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