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Old 22-04-2013, 09:19   #1
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Troubleshoot low fresh water pressure

Hi, I am trying to run down a low water pressure problem on my boat. We have a single sink and shower. There is a RV water filter on the cold side of the sink. Barely any water will come out of the cold water at the sink. The hot water is not much better..I can put my thumb over the outlet and easily close off the hot water. The pump is an older Jabsco 36950-2000 I believe it is called a piston pump. The pump cycles as expected. There is an accumulator at the discharge of the pump. There is a tap at the discharge and I'm going to check pressure there. I am suspecting the pressure is just low coming out of the pump. I can't find much literature on the pump I have. Is the pressure regulation done integral to the pump? It is very hard to access the pump and I believe will require removal of the hot water heater to get to it. I'd like to know for sure before I pull to rebuild the pump. Would be nice if it was just an adjustment. Previous owner indicated they had great water pressure. I have verified nothing clogged in strainer of supply going to the pump. Thanks.
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Old 22-04-2013, 09:26   #2
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Re: Troubleshoot low fresh water pressure

Rebuilding that pump isn't that big a deal. You can easily check its flow by unplugging the system near the discharge. It should pump 3GPM, so see how close it comes to filling a gallon bucket in twenty seconds.
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Old 22-04-2013, 09:34   #3
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Re: Troubleshoot low fresh water pressure

Does the pump run with the faucets off and build up pressure and then shut off on it's own?
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Old 22-04-2013, 13:03   #4
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Re: Troubleshoot low fresh water pressure

Quote:
Originally Posted by Bash View Post
Rebuilding that pump isn't that big a deal. You can easily check its flow by unplugging the system near the discharge. It should pump 3GPM, so see how close it comes to filling a gallon bucket in twenty seconds.
Using the hot water side of the faucet there is no way it would fill a gallon up in 20 seconds. I will time it just to see how long it takes.

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Does the pump run with the faucets off and build up pressure and then shut off on it's own?
It does run and build pressure and shuts off with nothing opened. Once I open something up the water will run for 20-30 seconds and then the pump will come back on to build the pressure back up. The flow does decrease the longer I keep the tap open.

Will measuring the pressure at the outlet of the pump allow me to determine which component is faulty? I am guessing at this point that either the pump needs a rebuild or the pressure regulator needs repair/replacement.

Thanks for the replies!
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Old 22-04-2013, 13:19   #5
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Re: Troubleshoot low fresh water pressure

it might be that your accumulator tank has too much water in it and needs to be drained. When that happens you have poor water pressure in your lines. Draining the tank might improve things.
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Old 22-04-2013, 13:22   #6
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Re: Troubleshoot low fresh water pressure

Is it like a house accumulator? If I remove it from the mount it should feel light like there is not much water in it?
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Old 22-04-2013, 13:47   #7
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Re: Troubleshoot low fresh water pressure

I'm with Astrid. Sounds lilke your accumulator. These things internally have two sides and a diapharm. one side for water and the other for air. Could be your diaphram is leaking or the air side of the accumulator has leaked air.

First is check the air pressure - there should be a valve (use a tire gauge or somthing similar). If there is no or low pressure, fill it and see what happens the nexzt couple of weeks. If the water pressure falls off again, you have a diaphram leak (or a leaky valve)
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Old 22-04-2013, 21:56   #8
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Re: Troubleshoot low fresh water pressure

To me, this looks like an opportunity to upgrade pumps. We've been using a variable speed Jabsco pump for about 4 years. No need for an accumulator either. Kill 2 birds with one stone.
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Old 23-04-2013, 04:34   #9
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Re: Troubleshoot low fresh water pressure

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Originally Posted by bstreep View Post
To me, this looks like an opportunity to upgrade pumps. We've been using a variable speed Jabsco pump for about 4 years. No need for an accumulator either. Kill 2 birds with one stone.
Damn, wot I was gunna write!


No need for accumulators anymore.

Reduce all the things in the system and it will be an easier system to use and maintain. Same with the in line filter. Why do you have one? Rip it out.




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Old 23-04-2013, 05:08   #10
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Re: Troubleshoot low fresh water pressure

ok, I'll check the accumulator as suggested. However even with the acccumulator as a problem the pump should still provide the gallon in 20 seconds correct? If I removed the accumulator completely by my understanding the punp would just run every time you cracked open a valve. Accumulator also prevents "hammering". Definitely keeping the inline filter..where my pump is you will not be able to remove the one on the pump and clean it without removing quite a bit of other gear to get in there. Thanks.
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Old 23-04-2013, 09:53   #11
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Re: Troubleshoot low fresh water pressure

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ok, I'll check the accumulator as suggested. However even with the acccumulator as a problem the pump should still provide the gallon in 20 seconds correct? If I removed the accumulator completely by my understanding the punp would just run every time you cracked open a valve. Accumulator also prevents "hammering". Definitely keeping the inline filter..where my pump is you will not be able to remove the one on the pump and clean it without removing quite a bit of other gear to get in there. Thanks.
Yeah, the acumulator might give you more pressure at first, but then all backs off to pump out put. If you have one of those small ish plastic accuulator they arent good for much but keeping the hammering away. Is this a new problem? a new boat?
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Old 23-04-2013, 09:59   #12
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Re: Troubleshoot low fresh water pressure

Newish problem old boat. It had poor pressure when we got the boat and we cruised it last year and just dealt with it but getting bothersome now. It does have a small plastic accumulator about a quart in size.
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Old 23-04-2013, 10:35   #13
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Re: Troubleshoot low fresh water pressure

The accumulator is there to even out the water pressure. without it, the water would come in spurts each time the pump cycled (unless it is a rotary pump).You say there is a drain valve right after the pump. hook a hose on it and the other end into a bucket. start the pump and run for a minute. now see how much water you have.

this will tell you if the pump is shot. sometimes they are worth rebuilding, sometimes not, especially if you want to increase your flow beyond what this pump is supposed to give.

good ludk
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