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Old 09-04-2019, 04:59 PM   #1
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Unhappy Water Pump or something else?

I have an issue with my 1981 Canoe Cove 41 Sedan (liveaboard) fresh water system. The boat has a single head with one vanity sink and a shower, as well as a galley sink.


“Normal” operation:

Galley Faucet: Water pump runs continuously when either the Hot or Cold Tap is used.
Vanity Faucet: Water pump runs continuously when either the Hot or Cold Tap is used.
Shower: Water pump runs continuously when either the Hot or Cold Tap is used.

Intermittently since I’ve had the boat:

Galley and Faucets: Normal
Shower: The water pump pulses on for several seconds and then shuts off for a second. Hot water runs continuously while cold water ebbs and flows with the pulse of the pump. I could get rid of the pulse and keep the pump running continuously by running the Vanity’s cold water tap. Increasingly I’ve had to take showers running in this configuration.

The past week:

Galley Faucet: Water pump runs continuously when either the Hot or Cold Tap is used.
Vanity Faucet: Water pump pulses on and off. Low water pressure from both vanity taps.
Shower: Cold water pulses on and off in approx 5 second intervals. The trick of running the cold tap on the vanity to get sustained water pressure no longer works. Learning to take showers dodging the periodic blast of scalding hot water.

I suspect that in terms of the water line runs, the galley is closest to the pump, followed by the vanity sink and then the shower.

Is my water pump on its last legs or could something else be at play here?

The pump is is a ShurFlo 2088-433-344 (3.3 GPM) and the tiny (quart sized) accumulator is made by Jabsco, model 30573-0000.

Lastly, there are neither signs of leakage nor water in the bilge.
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Old 09-04-2019, 05:13 PM   #2
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Does the pump manual say it's right to use an accumulator with it?

We have the small Jabsco accumulator, but it's matched to a Jabsco pump that's supposed to work with an accumulator.

But then there are some pumps that aren't meant for use with an accumulator...

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Old 09-04-2019, 05:22 PM   #3
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Does this model have a pressure adjustment screw? If so, try adjusting it to not pulse during low flow.
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Old 09-04-2019, 05:42 PM   #4
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If you do have a accumulator the pressure in it needs to be correct or the water temperature can fluctuate. Check your owners manual.
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Old 09-05-2019, 06:22 AM   #5
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AS a liveabord your water system is super important.
I would just purchase a new pump , and install a larger accumulator tank.

Remember a year of liveaboard may be 10 seasons of normal pump use .
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Old 09-05-2019, 07:06 AM   #6
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Personally, in the name of simplicity, I don't bother with an accumulator. I've tried the fancy variable speed pumps, but with my water pump in the engine room, they don't last. Controllers can't handle the heat and fail. Yes, a normal pump cycles on/off and pulses at low flows when running only cold water (hot water tank provides some buffering) but it's only a minor annoyance and not an actual problem.
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Old 09-05-2019, 07:51 AM   #7
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Since the water system is so important, it's not a bad idea to install a new water pump that is designed for use with an accumulator and a new, larger accumulator tank. In the end, you will appreciate it. Keep the old water pump around for an emergency spare.

That being said, it sounds like something is gradually reducing the flow. You've probably already checked for this but look for a small inline filter in the water line just before the pump. Those can clog up from sediment. Especially if a boat has sat for a while, water tanks can develop calcium-like deposits in them. New owner comes along and starts moving the boat around more. The deposits break loose and get sucked into the line, clogging the inline filter. One boat I worked on had similar symptoms. We cleared out the inline filter and it was still happening. Took the inspection port off the top of the water tank and found the water pickup tube was clogged with sediment "flakes." Blew out the pickup tube, cleaned out the tank, and it was never a problem again.

Let us know what you find.

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Old 09-05-2019, 12:25 PM   #8
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Quote:
Originally Posted by FF View Post
AS a liveabord your water system is super important.
I would just purchase a new pump , and install a larger accumulator tank.

Remember a year of liveaboard may be 10 seasons of normal pump use .
Another option IF you can use 120 VAC for the pump instead of a 12-volt pump. I wnet through three pumps (with accumulator) before opting for a 120 VAC pump. Consider a Grundfos MQ-3-35 3/4 horse pump. Costs about $600 but it will the last pump that boat ever sees. It has its own internal reservoir so your accumulator can be removed. The unit is rather large but you would gain some space getting rid of the accumulator and related plumbing. Installed one about a year ago and couldn't be happier. Turn on the water, the pump comes on moments later and you get a steady, even pressure stream of water.

The pump is actually designed to supply water from a lake or similar uses so, on a boat, it is bullet-proof. You could also use a 120 VAC shallow well pump plumbed to your accumulator which would be a less expensive alternative. After having the Grundfos and struggling with the 12-volt pumps, I would never have a boat without a Grundfos or a shallow well pump set-up.
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Old 09-05-2019, 01:54 PM   #9
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Originally Posted by catalinajack View Post
Another option IF you can use 120 VAC for the pump instead of a 12-volt pump. I wnet through three pumps (with accumulator) before opting for a 120 VAC pump. Consider a Grundfos MQ-3-35 3/4 horse pump. Costs about $600 but it will the last pump that boat ever sees. It has its own internal reservoir so your accumulator can be removed. The unit is rather large but you would gain some space getting rid of the accumulator and related plumbing. Installed one about a year ago and couldn't be happier. Turn on the water, the pump comes on moments later and you get a steady, even pressure stream of water.

The pump is actually designed to supply water from a lake or similar uses so, on a boat, it is bullet-proof. You could also use a 120 VAC shallow well pump plumbed to your accumulator which would be a less expensive alternative. After having the Grundfos and struggling with the 12-volt pumps, I would never have a boat without a Grundfos or a shallow well pump set-up.
We went the same route and installed a Headhunter Mach 5 120v pump. No more water hammer, and excellent pressure.
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Old 09-06-2019, 02:56 AM   #10
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Is the water pulsing while the pump is running or is the pump pulsing on and off ?
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Old 09-06-2019, 05:40 AM   #11
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"I don't bother with an accumulator."

The accumulator serves 3 purposes.

One is to be a place for the water in the water heater to expand so it does not raise the system pressure to require the T&P valve to release pressure.

Second it is to absorb the higher pressure that comes from the pumps momentum after it is cycled off by the pressure switch.

It also if large enough can provide water with out switching the pump on , which at low flows will short cycle the pump and pressure sensor.

All DC pumps are harder on the contacts in the pressure sensor than AC pumps.
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Old 09-06-2019, 07:47 AM   #12
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For those reasons, yes, an accumulator is theoretically necessary. But I've never had the water heater pop the T&P valve even heating up from cold. And I've never had an issue with short pump switch lifespan, so I haven't worried about that part.
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Old 09-06-2019, 04:26 PM   #13
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I will bet the shower has a flow restrictor and is insufficient to keep the pump running. You might try removing the restrictor or replacing the head with one that permits higher flow.
If the other faucet flow is steady above should fix the shower pulses.
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Old 09-08-2019, 05:52 AM   #14
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From google,but a working accumulator does all this.


Install an Air Chamber

Another very simple method of curing air hammer is to install a short segment of vertical pipe near the valves that are causing the water hammer. Known as an air chamber, this method creates a segment of empty, air-filled pipe that provides a cushion for water to rebound into when it wants to change directions suddenly. An air chamber is often fabricated onsite by the plumber as he or she installs the plumbing system, using ordinary pipes and fittings. Or, you can buy commercial air chambers, which are really just short stubs of pipe that are already capped.



Either way, an air chamber is comprised of a tee-fitting that connects to the main plumbing pipe, with a short run of horizontal pipe that then leads to a section of capped vertical pipe roughly 6 inches long. Because this dead-end pipe is located outside the main water flow, it traps a pocket of air.



In operation, when a faucet or other water valve shuts off quickly, the air in the chamber compresses temporarily under the water pressure, absorbing the shock that otherwise would go into the pipes and cause them to bang. In many homes, the air chambers are located near the wash tub alongside a washing machine, a common source of water hammer. But it is wise to install air chambers at critical spots throughout a building. Local building codes may require them at prescribed locations.



One problem with an air chamber is that they can become filled with water and cease to function correctly. This can be corrected by periodically draining the entire water supply system, which will restore the air to the chambers. To recharge the air chambers:


  1. Shut off ​the main water valve to the home.
  2. Open the building’s uppermost water faucet.
  3. Drain all water from all pipes by opening the lowest water faucet, normally located in the front yard or the basement of a building. As the water drains out, air will flow into the system through the uppermost faucet, automatically adding air back into the air chambers.
  4. Once water has stopped flowing from the lowest water faucet, turn it off, and open the main water valve. Keep the uppermost faucet open until water rises through the system and flows out its spout. Although the rest of the pipes will now be filled with water, the air chambers will remain full of air, restoring their shock-absorbing capacity.




On very rare occasions, air chambers can become clogged with minerals or other debris. They can be cleaned by removing the caps and scouring them out. Installing air chambers that are larger in diameter than the main plumbing lines can also help prevent clogging.


  • Note: In some areas, building codes may rule out air chambers in favor of mechanical water arrestors or other methods.


Installing Mechanical Water Shock Arrestors

Mechanical water shock arrestors are a more sophisticated form of absorbing the shock from water hammer. They work well in situations where air chambers are impractical. Water arrestors are sealed units that contain a spring and air bladder that absorbs water movement to mitigate the effects of water hammer. They are the preferred alternative in commercial buildings and for high water pressure applications. Mechanical water arrestors do not need to be recharged like air chambers, but they will need to replaced at the end of their life cycle, when the inner springs and bladders wear out.


Water hammer arrestors can be integrated into utility sink faucets or washing machine valves. They usually have compression or screw-on fittings for easy installation.


Mechanical shock arrestors are manufactured to a nationally recognized standard from the Plumbing and Drainage Institute, known as PDI - WH201, which also includes a method of sizing these devices.
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