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Old 08-03-2014, 08:57 PM   #1
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Plumbing problem...

Replaced my fresh-water pump with one of higher volume and now the accumulator tank is not working the way it used to. The water flow goes up and down while the pump is constantly cycling. While I am limited to 10 PSI on the accumulator tank, I can lower the pump pressure at the pump head.
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Old 08-03-2014, 09:37 PM   #2
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Get a larger tank that you can adjust the tank pressure correctly on.
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Old 08-03-2014, 10:46 PM   #3
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See if there's a shrader valve on the tank to check the psi on it. Those tanks have a diaphragm of some sorts that needs to have air on the other side pushing against the water column so that the pump doesn't have to cycle so often. If so, check the pressure and adjust to be a few psi below your cut in pressure. If you cant' adjust, as Capt Bill said, you'll need a new tank.

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Old 08-03-2014, 10:48 PM   #4
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The accumulator tank should be pressurized to just less than the turn on pressure of the pump.
Why can't you pressurize yours to more than 10 psi?
What kind of pump did you install?
What is the pumps pressure range?
What brand is the accumulator tank?
How big is it?
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Old 08-04-2014, 02:48 AM   #5
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According to a previous post, it was a throwaway from someone else's boat. Maybe the mechanic knew something you (ancora) didn't after all..? Are you sure the accumulator tank only handles up to 10psi, even my Shurflo takes 20psi.
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Old 08-04-2014, 08:24 AM   #6
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Those tanks can fail. The diaphram (bladder) can rupture or develop a leak. Mine did recently. Check the air pressure and if it's zero or water comes out when you try to check it, it may be ruptured (if water comes out the air fitting, it is ruptured). Set it to the correct pressure and see if it holds or the pressure drops again.
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Old 08-04-2014, 08:35 AM   #7
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If you need to replace the accumulator/expansion tank, you can get an economical replacement at one of the home stores for less than $50.

Watts 8.5 in. W x 11.5 in. D x 8.5 in. H Pre-Pressurized Steel Water Expansion Tank-DET-5 at The Home Depot
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Old 08-04-2014, 09:33 AM   #8
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If you need to replace the accumulator/expansion tank, you can get an economical replacement at one of the home stores for less than $50.
Or you can replace the existing one and have a much easier time of connecting and mounting it. I replaced mine in ten minutes or less. It has push in fittings.
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Old 08-04-2014, 10:51 AM   #9
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The pump replacement and tank problem seem coincidental. Wrong pump without the correct pressure limiter per chance. Is the tank bladder pumped up?
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Old 08-05-2014, 11:03 AM   #10
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It is a Jabsco accumulator tank that I replaced two months ago. Didn't check the air pressure as it worked just fine with the previous lower pressure pump. According to the brochure, "The tank, which can be pressurized to 10 PSI, can be fine tuned to any system." I guess it's a matter of getting the air pressure just right.
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Old 08-05-2014, 01:18 PM   #11
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It is a Jabsco accumulator tank that I replaced two months ago. Didn't check the air pressure as it worked just fine with the previous lower pressure pump. According to the brochure, "The tank, which can be pressurized to 10 PSI, can be fine tuned to any system." I guess it's a matter of getting the air pressure just right.
If it's one of those small black plastic tanks it my be to small, volume wise, for your new pump. Plus 10 psi max is not going to be enough pressure.
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Old 08-05-2014, 01:25 PM   #12
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Jabsco makes five or six different accumulator tanks. Even the small plastic ones can be pressurized to a maximum of 125 psi. The small plastic ones are pre-charged to 10 psi. You can raise the pressure to the turn on pressure of the pump without problem.

Even at the pre-charged pressure of 10 psi it should function. I wonder if the diaphragm in the tank is defective and the tank is waterlogged with no room for air?

Typically small water system pumps are set to turn on at 20 to 30 psi and off at 40 to 60 psi.
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Old 08-05-2014, 01:31 PM   #13
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Like Bill says, it may be just too small for your new higher volume pump.
In which case the pump would cycle on and off very quickly.
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Old 08-05-2014, 02:28 PM   #14
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The little JABSCO accumulator tanks are more pulsation dampeners than anything else. They tend to remove the pulsations that the pump creates during pumping, and smooth out the water delivery. Kind of a hydraulic shock absorber. Mine say charge the bladder to a max of 10 psi. If you want to retard the on/off frequency of the pump you need a tank and bladder with more volume. The more volume the longer the cycle time.
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Old 08-05-2014, 03:05 PM   #15
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Like Bill says, it may be just too small for your new higher volume pump.
In which case the pump would cycle on and off very quickly.
That depends on the amount of water flowing and that in turn is dependent on the faucets or appliances using the water. The pump may be capable of higher volume than the one it replaced but it's not delivering more water unless more faucets are opened at the same time.
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Old 08-05-2014, 03:07 PM   #16
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The little JABSCO accumulator tanks are more pulsation dampeners than anything else. They tend to remove the pulsations that the pump creates during pumping, and smooth out the water delivery. Kind of a hydraulic shock absorber. Mine say charge the bladder to a max of 10 psi. If you want to retard the on/off frequency of the pump you need a tank and bladder with more volume. The more volume the longer the cycle time.
The small tank does what it's supposed to do and that is reduce the number of times the pump has to start and keep it from chattering on and off when a small amount of water is being drawn. If the tank holds a quart, you can draw most of that quart before the pump comes on again.
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Old 08-05-2014, 04:47 PM   #17
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The small tank does what it's supposed to do and that is reduce the number of times the pump has to start and keep it from chattering on and off when a small amount of water is being drawn. If the tank holds a quart, you can draw most of that quart before the pump comes on again.

My sense is that you are right and that small tank holds just about a quart. I also sense that with a 10 psi quart bladder compressed further to about 40 psi takes up a lot of that quart. You must begin to see that there is not much water to use before the pump cycles again. A larger tank would keep the pump off longer.
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Old 08-05-2014, 06:25 PM   #18
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I would love to see a pulsating discharge from a faucet from one of these pumps...I have never seen it happen on any boat I've ever been on even the ones without accumulators like mine...either fresh or washdown water pumps.
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Old 08-06-2014, 01:20 AM   #19
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"The small tank does what it's supposed to do and that is reduce the number of times the pump has to start and keep it from chattering on and off when a small amount of water is being drawn. If the tank holds a quart, you can draw most of that quart before the pump comes on again. "

Very clear description of what the tank does.

In a situation where a small amount of water is being drawn, say one quart per minute from the one quart tank, the pump would turn on every minute. The larger the pump capacity, the shorter that run will be.

Say we have a small 2.5 gallon per minute pump. It would replace that quart of water with a run time of a little over 10 seconds. A 5 GPM pump would only need to run a little over 5 seconds to replace that quart. Each pump would have to turn on four times to supply a gallon of water but the run time of the larger pump would be shorter.

Then the question becomes what happens if we double the size of the tank to two quarts? Now both pumps have to run longer to replace the two quarts but they only need to turn on twice to pump a gallon of water.

I think that the switch will last longer with the larger tank as it is the on / off cycles that wear it out, not the total run time.

Without a tank or with a waterlogged tank, both of these pumps would chatter on and off, as Ron described, fast enough to damage the switch in a short time.

Accumulator tanks are important when using a pressure switch controlled pump. Bigger tanks are better than small ones. In the end you choose the tank you have room for.
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Old 08-06-2014, 01:21 AM   #20
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Oh no! I just re-read the original post. The problem sounds exactly like what happens when you install a variable speed pump and don't remove the tank.
We need to know what the pump is.
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