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Water pumps 25psi v 40psi?


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Out of curiosity, I asked a question to a large online supplier (not MC) about the following two water pumps as follows:

 

https://www.asap-supplies.com/products/jabsco-31620-0092-par-max-4-pressure-pump-12v-16-lpm-40-psi-509737

 

https://www.asap-supplies.com/products/jabsco-31620-0292-par-max-4-pressure-pump-12v-16-lpm-25-psi-509736

 

My question was on the lines of .......

"Given that the flow rate of 16 litres/min is the same for both models, why/when would you specify the 40psi version over the more common 25psi?

 

Their answer:

 

"This would depend on what your system uses and what capacity it is capable of running. But, assuming both are fine, the higher pressure pump would pressurise a little slower, whilst the 25psi would pressurise faster, so out of the two, I would say the 25PSI would be a better option."

 

Given that the pressure in a fluid is equal in all directions, I still don't get it. Surely the 40psi version will still hit 25psi in the same/similar time as the 25 psi version would but the 40 psi would keep pumping until it reaches 40 psi in the system. I can understand this on a superyacht that's 100m long but is there more to this?

 

Edited by Markinaboat
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Firstly it would be a very bad idea to fit a 45psi pump to a boat system with calorifier expecting max 30psi. Best case scenario would be the PRV opening permanently, worst case the calorifier splitting!

 

The advantage of a higher pressure pump (coupled with the rest of the system designed for high pressure) is the ability to achieve a good flow rate through long narrow pipework and or up to upper deck levels, through restrictions such as showers etc. But on a typical narrowboat you get a perfectly adequate flow rate with a 25psi one.

 

I would agree with you that the answer you received is mostly BS, but then what do you expect, they just sell ‘em, they don’t design ‘em!

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27 minutes ago, nicknorman said:

Firstly it would be a very bad idea to fit a 45psi pump to a boat system with calorifier expecting max 30psi. Best case scenario would be the PRV opening permanently, worst case the calorifier splitting!

 

The advantage of a higher pressure pump (coupled with the rest of the system designed for high pressure) is the ability to achieve a good flow rate through long narrow pipework and or up to upper deck levels, through restrictions such as showers etc. But on a typical narrowboat you get a perfectly adequate flow rate with a 25psi one.

 

I would agree with you that the answer you received is mostly BS, but then what do you expect, they just sell ‘em, they don’t design ‘em!

Yep, there's no way I would put a 40 psi in with the typical nb system for the reasons you state. On the other hand, I would've thought that there were perhaps far superior 'lumpy-stuff' pumps that would be specced in your average $10m super-yacht!

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