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Old 08-06-2014, 06:43 AM   #21
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A large sized bladder tank can be stuck in an almost inaccessible place , so a home 6 to 20 gal size could be used.

Even if the supply like is 30 ft , it will still do its job.
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Old 08-06-2014, 07:54 AM   #22
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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.
Yes it would but there are space constraints on many boats. I had a 30 gallon pressure tank in my former home. Like anything on a boat (or in like), there are compromises to be made.

If you are curious as to how much water your tank holds, run water until the pump starts. Turn the water off and wait until the pump stops. Put a container under the faucet and run water until the pump starts again. Quickly turn the water off, then measure the amount in the container.
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Old 08-06-2014, 12:37 PM   #23
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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.
It does happen. Seen it a number of times over the years. Less so as pumps have gotten better perhaps.
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Old 08-06-2014, 12:42 PM   #24
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The little Jabsco tank is just a pulsation damper and really should not be considered an accumulator tank. At least IMO.
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Old 08-06-2014, 01:24 PM   #25
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Note, there is a difference between an "expansion tank" and an "accumulator/pressure tank". An expansion tank allows for expansion of heated water at or near the water heater. These are typically about 8" x 10" and hold a small (quart or two) of water. An accumulator or pressure tank is larger and provides pressure to the water system when the pump is not running by pre-charging (compressing) a air bladder within the tank. The accumulator tank should have a air valve for initial charge of air to fill the bladder and to make later adjustment if necessary. It will be labeled with the volume of water held at a given pressure setting and a "draw down" volume. The tank is only about half full of water at full charge.
The smallest of these that I have seen are about 2.5 gallons-looks about like a propane tank and typically has a tank tee fitting at the bottom for water.
Like the prior post states if you replaced your pump with a variable speed (flow demand) type pump NO ACCUMULATOR TANK IS REQUIRED NOR PRESSURE SWITCH. Many of the newer pumps are variable speed and usually say something about "sensor" in their advertising. The pump itself has a pressure sensitive device that speeds the pump up when the pressure drops which is as flow demand increases. To test which style pump you may have installed open one faucet a very slight amount and listen to the pump, open several faucets at max flow and see if the pump motor speeds up. If it does then you have a variable speed pump if it runs at a constant speed no matter what the demand (flow) is then you need an accumulator tank and pressure switch.
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Old 08-06-2014, 01:32 PM   #26
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Jabsco Accumulator Tank

Pressure: 125 Psi, Volume: 1 Liter
Tank

Item #: 500718

A more compact pneumatic bladder tank to fit smaller systems or spaces.
Extends pump life!
Reduce water system pulsation and rapid on/off pump cycling.
Mount Horizontally or vertically or upside-down.
Can be fine-tuned to each system.
No. 12573 Has removable plug in top for draining or winterizing.
It includes both 1/2" barbed hose and 1/2 threaded qestTMsnap-in port fittings.
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Old 08-06-2014, 07:43 PM   #27
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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.
Mine did this at less than full flow until I installed an accumulator tank. When it started again, I knew the tank had failed. When I replaced the tank the problem went away again.

The pulsing (the pump starting and stopping rapidly) caused a couple pumps to fail prematurely.
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Old 08-06-2014, 08:16 PM   #28
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Ron:
How long between the tank replacements?
The common failure is the bladder losing it's integrity. Do you have a filter prior to tank? I would expect to get about five years even in a marine environment.
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Old 08-07-2014, 07:12 PM   #29
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Ron:
How long between the tank replacements?
The common failure is the bladder losing it's integrity. Do you have a filter prior to tank? I would expect to get about five years even in a marine environment.
I would have expected it to last pretty much "forever". The ones in my previous home failed by rusting. We had acid water.

There is a filter before the pump so that's before the tank. I think the tank was only a couple years old. I was on a cruise when it failed so I replaced it but haven't gotten around to examining the failed one. I suppose the bladder might be available as a repair part.
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Old 08-07-2014, 08:54 PM   #30
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I have never replaced a bladder in one before. Usually just replace the whole thing. The ones we typically use on our water systems is much larger than those in boats (60 gallons or more) and now are fiberglass - no rust. I know that one sign that the bladder is compromised is that you will not only start noticing the surge/cycle but also milky looking tap water for a moment or two. Water and air mix.
Good luck, I was just curious.
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Old 09-10-2014, 10:19 AM   #31
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I read this whole thread, and several others I've found on pulsing/cycling pumps.

Half-way through this season, the ShurFlo 4 GPM potable water pump I installed last summer started cycling or pulsing rapidly when any faucet was used. It pulses on/off a little faster than once per second.

The manual claims no accumulator tank is needed, and so I didn't install the one I bought, mostly because it will take a significant bit of plumbing re-work.

The manual says "The pump operates normally up to about 30-psi [2.06 Bar], where a spring-loaded by-pass valve opens, allowing flow back from the output side to the input side, providing smooth, steady flow with virtually no cycling, all the way down to a trickle. As a faucet is opened back up, the pressure will drop, the by-pass will close and full flow is again obtained. This allows good flow, even with today's restrictive showers and pullout sprayer faucets."

So, why did it start cycling or pulsing all of a sudden?

My first thought was that the above is all BS, and I really do need to install the accumulator. Maybe my hot water tank was acting as an accumulator until the last bit of air at the top of the tank finally made its way out into the lines or was absorbed into the water.

My question is: Is this a normal failure mode for these pumps? Maybe adding the accumulator won't help.
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Old 09-10-2014, 12:11 PM   #32
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I think you've got a problem with the by-pass valve. If the by-pass fails the pump becomes just a regular dumb on and off pump and would cycle as you've described. If the pump is still under warranty, take it back to the dealer. If it's out of warranty, call ShurFlo and see if they can give you help in fixing it. Of course the third option is to do what I would do. Take it apart, be unable to put it back together, and buy a new one.
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Old 09-10-2014, 12:34 PM   #33
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Sounds like it is broken. These pumps are somewhat famous for having this problem. Hopcar is right give them a call they are usually helpful.
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Old 09-10-2014, 05:58 PM   #34
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I called ShurFlo. Spoke to a native English speaker right away. She suggested turning the set screw in (clockwise) on the bypass valve one complete turn.

It worked. The pulsing has stopped, and I get a steady stream down to a trickle (at which point it cycles again, but that's OK.)
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Old 09-10-2014, 11:43 PM   #35
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Thanks for sharing that. Now if one of my customers has that problem I'll know what to suggest. I always learn something useful on this forum.
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