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thesternbow

accumulator and water pump

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First question :-

Is there a standard size water pump for 57' boat. (What manufacturer ?) 

Secondly, what size of accumulator would be needed with this pump ?

 

Oh and where can I find what a typical setup looks like?

 

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34 minutes ago, thesternbow said:

Oh and where can I find what a typical setup looks like?

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1 hour ago, thesternbow said:

First question :-

Is there a standard size water pump for 57' boat. (What manufacturer ?) 

Secondly, what size of accumulator would be needed with this pump ?

 

Oh and where can I find what a typical setup looks like?

 

The purpose of an accumulator is simply to stop the pump cutting in and out rapidly when the tap is partially open (or rather, when the pump can supply more water than is demanded). Big accumulator = slow cycling of the pump, small accumulator = faster cycling. There is no right answer, 5 litres seems common, although 2 litres would probably do at a pinch.

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13 hours ago, thesternbow said:

Is there a standard size water pump for 57' boat. (What manufacturer ?

There isn't a standard size. Two figures are output pressure and flow rate. Set the output pressure with respect to the calorifier, assuming you are going to fit one. It needs to be less than the safe working pressure of the calorifier. Flow rate depends on if you are fitting a shower and how far away that shower is from the pump, size of pipes from tank to pump and from pump to shower. The higher the better for a belting shower, but this uses more water, so more frequent visits to a water point.

On manufacturers, Shurflo are cheap, but don't seem to last long (except @blackrose, who has an immortal water pump). Jabsco seem to be a bit better quality than shurflo these days. Other manufacturers exist, but these are the most common. I've currently got a Jabsco parmax 25psi 11l/min pump on my 57' NB, but this fills a small bath tub, rather than a shower.

 

What @nicknorman said concerning accumulators.

Jen

Edited by Jen-in-Wellies

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2 hours ago, system 4-50 said:

And some types of water pump don't need an accumulator at all.

From experience some of those which are advertised as not needing one, don't work properly if you do have one.

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1 hour ago, Keeping Up said:

From experience some of those which are advertised as not needing one, don't work properly if you do have one.

And from anecdotal evidence on here, some that are advertised as not needing one don’t work properly without one. ;)

  • Haha 1

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AS far as I know there are two types of pump that say they don't need an accumulator.  One type with a variable speed controlled by pressure probably works well without one but in the past some have been unreliable/short lived.  The other type has a bypass valve set to open just below pump cut out pressure that vents excess water back to the inlet side so in theory they can never reach cut out pressure but I have my doubts with low flows from the tap. I also think an accumulator would be an advantage under low flow conditions.

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2 hours ago, Keeping Up said:

From experience some of those which are advertised as not needing one, don't work properly if you do have one.

I'm curious. How does this manifest itself?  I would have guessed (without much thought) that it would have improved it further.

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2 hours ago, WotEver said:

And from anecdotal evidence on here, some that are advertised as not needing one don’t work properly without one. ;)

I’m rather thinking he meant the opposite but it was a typo? I read it the other way at first.
Or maybe not! Anyway, I agree with your point!

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2 hours ago, system 4-50 said:

I'm curious. How does this manifest itself?  I would have guessed (without much thought) that it would have improved it further.

IIRC (it was a few years ago) the pump would not turn on until the pressure in the system had dropped almost down to zero, because while the taps were turned off the pressure from the accumulator fed back through the sensing system, so that the pump retained pressure there even when the system pressure fell.

31 minutes ago, nicknorman said:

I’m rather thinking he meant the opposite but it was a typo? I read it the other way at first.
Or maybe not! Anyway, I agree with your point!

No, I meant it exactly as written!

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5 hours ago, Keeping Up said:

From experience some of those which are advertised as not needing one, don't work properly if you do have one.

Well, I have the ubiquitous Jabsco Par Max 2.9 which says on the box it doesn't need an accumulator.  It replaced a similar pump on a system with an accumulator and, despite what it says on the box, I replaced that too at the same time.  The system works exactly as one would hope and expect. I'd prefer to think the Par Max might manage without an accumulator if pushed, rather than shouldn't be fitted with one.

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