Markinaboat 64 Report post #1 Posted November 11, 2020 (edited) 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 November 11, 2020 by Markinaboat error Share this post Link to post Share on other sites
nicknorman 3871 Report post #2 Posted November 11, 2020 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! Share this post Link to post Share on other sites
Markinaboat 64 Report post #3 Posted November 11, 2020 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! Share this post Link to post Share on other sites
Tony Brooks 2853 Report post #4 Posted November 11, 2020 I agree with you and Nick - the answer was bullshine. Share this post Link to post Share on other sites
OldGoat 500 Report post #5 Posted November 11, 2020 51 minutes ago, Tony Brooks said: I agree with you and Nick - the answer was bullshine. It was a different outfit when the Edwards owned it. "Everyone's" bulshitting nowadays.... Share this post Link to post Share on other sites
Markinaboat 64 Report post #6 Posted November 11, 2020 4 hours ago, OldGoat said: It was a different outfit when the Edwards owned it. "Everyone's" bulshitting nowadays.... I don't believe you! 😁 Share this post Link to post Share on other sites
Ex Brummie 156 Report post #7 Posted November 11, 2020 I have a multipoint and a 40psi pump. It allows better thermostatic control in the shower. Share this post Link to post Share on other sites
Slim 328 Report post #8 Posted November 11, 2020 5 hours ago, OldGoat said: It was a different outfit when the Edwards owned it. "Everyone's" bulshitting nowadays.... These days is it not MC under another name? Share this post Link to post Share on other sites
