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Old 11-13-2010, 07:45 PM   #1
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pulsating water pump

So I replaced our water pump right after we bought the boat a couple months back. *Old one worked for about a week and then it died. *New one is working well but I have noticed it seems to pulsate. *If you turn on any of the sinks, water flows good overall but it will pulsate as the pump kicks on for a moment, then off, then on, off, etc. so that pressure is variable. *Anyone else have this issue and what caused it? *All previous boats would run consistent pressure when sink or shower was turned on for a prolonged time (i.e. washing dishes or taking a shower) vs. pulsating pump turning on and off and creating pulsating water pressure. *
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Old 11-13-2010, 08:20 PM   #2
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RE: pulsating water pump

Some newer pumps have plumbing that reduces the pulsing a lot but one could put a little tank in the line that would be half full of air and that should make it as smooth as at home. Some body may make such a "surge tank". Put the question to TF*** ....you'll get ideas flack and everything. I bought the $250 deluxe pump and had smooth water but the pump died after 4 mo so I bought the cheap $120 pump (just a bit more pulse that the $250 but has worked great for much more than 4 mos. Do you have the old one w the toothed belt? They ARE pulsy. The old ones could be rebuilt forever but I got the newer kind. I think I'll make a washdown for the anchor w the old pump.
Your boat looks wonderful in your new avitar.
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Old 11-13-2010, 08:36 PM   #3
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pulsating water pump

Eric,
The water pump is not more than 60 days old and I bought it brand new from west marine (old one died on a saturday night and wife wanted a shower Sunday a.m. so had to get it done quick). It's your typical modern pump...plumbed exactly as the old one was. Only difference is that this one is brand new and old one was rated for 3.8 and this new one is a 4.0 gallons. It shouldn't be pulsing so much and while it works fine, it is starting to irritate me!

Thanks for the kind words re: my new avatar. I took that pic yesterday as we were anchored out on the TN River and playing around in the kayak. I still need to get the boom installed but at least I finally got the mast up!

P.S. just crawled down into the bilge to confirm the make of the pump and noticed a slight wetness under it...feeling around the underside of the pump housing is wet. *Maybe the pump is defective and I need to get a replacement. *I checked it multiple times after I installed it to make sure there were no leaks and this is the first time I've seen any water there. *Hmmmm....


-- Edited by Woodsong on Saturday 13th of November 2010 09:39:44 PM
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Old 11-13-2010, 09:13 PM   #4
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RE: pulsating water pump

Most likely if you install a small 2 lt accumulator tank in the system (tank with small pressure bladder inside) you will get constant pressure.
Available at your local chandler.

Benn
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Old 11-14-2010, 06:29 AM   #5
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RE: pulsating water pump

The crappy small Jabsco accumulators need to be drained every so often.

The bigger house units can loose their pre charge , get a tire pressure checker , turn off the water system , open a faucet till there is no flow.

Then measure the pressure at the schrader valve on the top of the accumulator .

IT SHOULD BE AT THE LOW PRESSURE CUT IN ,

if not a bike tire pump will restore the pressure.
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Old 11-14-2010, 08:54 AM   #6
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RE: pulsating water pump

you can get a small expansion tank at home depot... about $ 60 if* I remember... it will take out all the pulse of the pump. We had one until I replaced the pump wwith a new VSR pump. The pump didn't like the pressure tank for some reason... so I pulled the tank and the pump was happy and the Admiral was happy as the shower doesn't pulse.
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Old 11-14-2010, 03:31 PM   #7
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RE: pulsating water pump

Hollywood, are you talking those small blue expansion tanks they use at hot water heaters on a house like this:
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

Looks like they sell this one too for about 1/2 the cost:
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

Do I just install this on the outflow side of the water pump and just plumb it inline with that outflow line?
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Old 11-14-2010, 05:00 PM   #8
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RE: pulsating water pump

Page 2 of this Raritan manual shows a good diagram of how a water system should be set up including where to put the tank.
http://www.raritaneng.com/pdf_files/...eaterv0502.pdf
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Old 11-14-2010, 10:26 PM   #9
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RE: pulsating water pump

Woodsong,
The schematic Keith supplied is a great one, and the HD tank looks just fine. It should cure your pulsation issues.* The h.depot one works great, or you can get one from west marine that is 75% smaller for twice as much !
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Old 11-15-2010, 09:15 AM   #10
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RE: pulsating water pump

Keith,
thanks SO much for that link- exactly what I needed! I pulled the pump off the boat yesterday as it is definitely defective and leaking around the housing body- getting a replacement today and may pick up the expansion tank at HD and install it all at once. The weird thing is that the pump that was on the boat when I bought it did not pulsate and my 2005 sedan I sold this winter did not pulsate and neither one had an expansion tank.
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Old 11-15-2010, 09:21 AM   #11
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RE: pulsating water pump

A lot of the newer pumps don't require an Expansion tank.

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Old 11-15-2010, 01:29 PM   #12
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RE: pulsating water pump

If you didn't have pulsing before and you've replaced the old pump with the same kind of pump, the chances are the pulsing was from the leak in the pump that you have discovered. If the new replacement pump doesn't leak and you still get pulsing then I suppose the new pump could be enough different than the old one in terms of its innards that you now need an expansion tank. Or you can go with the kind of pump SD mentions that is variable speed and delivers the amount of water necessary with no pulsing and no expansion tank. They're not the cheapest things in the world, however.
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Old 11-15-2010, 02:28 PM   #13
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pulsating water pump

You should also be aware that many of the new pumps not only don't need expansion tanks but if you add one the warranty is voided. Chuck

-- Edited by Capn Chuck on Monday 15th of November 2010 03:28:35 PM
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Old 11-21-2010, 06:49 PM   #14
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pulsating water pump

Woodsong,


Maybe I missed it but what was the original pump?
What is the pump you are using now?



-- Edited by C lectric on Sunday 21st of November 2010 07:49:53 PM
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Old 11-22-2010, 09:55 AM   #15
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pulsating water pump

Some times*I hate these discussion.* I mean everything was fine, until I read this discussion and notice that our water pulsates a bit?* )-;* **The accumulator is 15+ years old so it probable needs replacing.* Oh will what is another couple boat unit in the bigger scheme of boating?* If I did not have a boat I would probable spend it on cloths or electronic toys of something?* Oh wait I already do that!

I thought the accumulator was so there was no sudden pressure on the lines.* In a domestic house the lines are capped several feet above the faucet so the air takes the pressuer and the*pipes dont bang/rattle.* West marine sells a 10 buck plastic one that connects to the pump.* So I can sill buy a new Holiday out fit!* (-;***


-- Edited by Phil Fill on Monday 22nd of November 2010 10:56:17 AM
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Old 11-22-2010, 03:59 PM   #16
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pulsating water pump

Quote:
Phil Fill wrote:I thought the accumulator was so there was no sudden pressure on the lines.
In a boat's FW system, the prime reason for having an accumulator is "to aid the FW
pump at peak demand."
The same reasoning holds true for having an accumulator in a hydraulic system. (Even with a constant speed-variable displacement pump, accumulators are still needed.)

*


-- Edited by SeaHorse II on Monday 22nd of November 2010 05:03:51 PM
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Old 11-22-2010, 08:32 PM   #17
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RE: pulsating water pump

The leak is probably the culprit. Pumps work by creating a partial vacuum at the inlet, then atmospheric pressure pushes the water in to the inlet to equalize the pressure. the leak is happening when the pump is shut off. when you turn it on the water no longer leaks out, but air leaks in because of the vacuum.

Although its also possible that your accumulator failed at the same time as your pump; but the odds are against it.

Good luck
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Old 11-23-2010, 05:13 AM   #18
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RE: pulsating water pump

In a boat's FW system, the prime reason for having an accumulator is "to aid the FW
pump at peak demand."

I disagree many pumps will self destruct if not fitted with an accumulator.

Living aboard in the old days for 22+ years the worst nightmare was the PAR pumps with tiny toothed belts.

The mass was so high that when shut off by the pressure switch the pump would continue to run , against uncompresable water.

SNAP, the eccentric would eventually go.

Second hassle was PAR used their own pressure sensor that had its own weird thread .

This was cured bu silver soldering a copper lead with a plumbing store end , and installing a Squared D pump switch.

With no accumulator the pump life was very short.

The happiest day of the liveabord (and RV ) community was the day Sureflo started to sell pumps 11
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Old 11-28-2010, 03:36 PM   #19
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RE: pulsating water pump

Quote:
FF wrote:SeaHorse Wrote:

In a boat's FW system, the prime reason for having an accumulator is "to aid the FW pump at peak demand."


FF Wrote:
I disagree, many pumps will self destruct if not fitted with an accumulator.
FF:
You just validated my statement. (Actually, it wasn't my statement but rather it was the Vickers people many years ago.) I was in the hydraulic business and used a lot of their pumps, etc.
*
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Old 11-29-2010, 07:28 AM   #20
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RE: pulsating water pump

Well in all the modern boats I've owned I've never had an accumulator tank whatsoever. I put the new water pump on earlier this weekend and darned if it is not still slightly pulsating....not as much as the previous one I installed, but still pulsing. It's a Jabsco "Par Max 4"- 4.3 GPM. Model 31620-0092.
I guess I need to install an accumulator tank but I sure would like to figure out why it is pulsing when no other modern pump I've had in past boats did this!
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