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-   -   Fresh water pump question (http://www.sailnet.com/forums/gear-maintenance/40169-fresh-water-pump-question.html)

poopdeckpappy 01-27-2008 05:29 PM

Fresh water pump question
 
Right now I have a 3gpm PAR belt driven fresh water pump, I want to install a 4.5-5 gpm pump to reduce the pulsation and increase output from the showerhead, is there a side effect I should be aware of ??, all lines are in good shape

lharmon 01-27-2008 06:03 PM

Do you have an expansion tank in your system? If not adding one of these should get rid of the pulsing. The expansion tank has an air bladder and stores a quanity of water at your systems pressure and will reduce pump cycles and the pulsing. If you have an expansion tank the bladder inside it may be flooded or the tank needs pumped up with air. You can also make sure your showerhead is a reduced flow model.

Good luck,

Valiente 01-27-2008 06:21 PM

That's an excellent idea. If you are happy with the flow rate, the expansion tank is a better solution and is easily maintained. We have an expansion tank in our gas furnace/hot water radiator house heating system. Occasionally we get "water hammer" and we simply go to the highest rad in the house and bleed off trapped air which is giving the system a fit of the wobblies.

Here's a brief explanation of the principles. The tank needed for a boat's plumbing could be quite compact.

http://en.wikipedia.org/wiki/Expansion_tank

Freesail99 01-27-2008 06:26 PM

Expansion tanks are often installed to stop water hammer, said the plumber's son.

bristol321 01-28-2008 05:38 AM

there is also a "mini" sized (roughly 1" diam. by 4" tall) anti-hammer valve. We use them on every new job now per code. Available at any plumbing supply house.

christyleigh 01-28-2008 08:27 AM

Quote:

Originally Posted by poopdeckpappy (Post 256739)
Right now I have a 3gpm PAR belt driven fresh water pump, I want to install a 4.5-5 gpm pump to reduce the pulsation and increase output from the showerhead, is there a side effect I should be aware of ??, all lines are in good shape

One thing that bit me in the wallet was my replacement of a struggling PAR belt driven pump was that I was un-aware of the Max PSI that my hot water heater pressure release valve was spec-ed for. I installed a Very High Pressure 51 PSI I think water pump last spring not knowing that my hot water heater said to only use up to 48 PSI. I didn't find that out until this fall reading up on my hot water heater to look at pressure valve replacement :o It worked fine for a while - although it was really too much pressure (splashing water in the sink) - then mid-summer the hot water heater pressure release valve started its own form of Hammering..... and I mean Hammering :eek: :eek: when the drain hose that was connected to it would jump around with the on and off release of pressure. Just last week I re- replaced it with a 40 PSI pump and I HOPE that when I reconnect the hot water heater in the spring that the relief valve will be happy :rolleyes:
Probably a rare issue but it took me by surprize so it seemed worth mentioning :)

JohnRPollard 01-28-2008 09:30 AM

Poopdeckpappy,

My gut feeling on this is that the higher pressure/volume pump will not solve the pulsing (might make it worse). Normally the problem you are having is addressed by adding the "expansion" tank mentioned above.

If you are having trouble locating an "expansion" tank, I thought I'd mention that in marine applications they are generally referred to as "accumulator" tanks. They are a fairly common component of domestic fresh water systems aboard sail and powerboats.

Sapperwhite 01-28-2008 09:33 AM

PDP,
I have a Jabsco 1 litre accumulator tank on my fresh water system and have good steady pressure, and no pulsation at all. Install is easy, if you have 1/2" water hose. You just have to find a good spot on the high pressure side of the pump and cut the hose. The two cut ends go on the hose barbs and the third point of the "T" is the tank itself.


Defender looks to have the best price on it too, but you should shop around first.
http://www.defender.com/category.jsp...1271&id=316442

Here is a pic of the Jabsco 1quart, 1 litre, and 2 gallon accumulators
http://www.marineparts.com/partspage...s/jabstank.jpg

christyleigh 01-28-2008 10:09 AM

Quote:

Originally Posted by JohnRPollard (Post 256949)
Poopdeckpappy,

My gut feeling on this is that the higher pressure/volume pump will not solve the pulsing (might make it worse). Normally the problem you are having is addressed by adding the "expansion" tank mentioned above.

Just to be clear - my post about my high pressure pump wasn't meant as a cure for your pulsing or mine as I have an accumulator tank. My pump either needed rebuilding or replaceing and I chose replaceing. I just wanted to share my self-generated problem in case someone does need or wants to replace a pump with something other than the one that came with the boat.

JohnRPollard 01-28-2008 11:27 AM

Quote:

Originally Posted by christyleigh (Post 256964)
Just to be clear - my post about my high pressure pump wasn't meant as a cure for your pulsing or mine as I have an accumulator tank. My pump either needed rebuilding or replaceing and I chose replaceing. I just wanted to share my self-generated problem in case someone does need or wants to replace a pump with something other than the one that came with the boat.

Stan, I too should have been more clear. My response was in reply to the OP's statement "I want to install a 4.5-5 gpm pump to reduce the pulsation". I understood that your post was alerting him to a possible "side effect" of a higher pressure pump. Hopefully with our respective clarifications he'll understand what we were each getting at.:)


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