Fresh water pump upgrade to 4.5GPM

[Skuza]

I didn't get much response within another thread so here goes.
I was thinking of upgrading the pump for a little more pressure during showers. Boaters World has them on sale (going out of business). The Jabsco is rated at 4.5GPM at 40psi. The original Shurflow is 3.3GPM at 45psi. Is the lower psi going to affect anything else in the water system? I think the pressure switch is located on the pump itself so that shouldn't matter but what about the accumulator tank? This is the standard type pump I'm considering and not the variable speed/on demand type.

 

[Four Suns]

The problem that will probably rear its ugly head is the fluctuation in water flow when you turn on a faucet. You may have to put their bigger expansion tank on the system to remove the surgingness (that's not a word) of the water at the tap. At the end of the day, your faucets only need so many GPM so if the pumps are way over rated, they are going to pump water into the system way too fast then shut off... then repeat... the expansion tank smooths that out... but the normal expansion tank on the system is pretty small and may not handle the increase you are suggesting (it won't hurt anything... it's just annoying).

 

[Skuza]

Would going from a 3.3 to a 4.5 be that big of a difference? If my math is right thats a ~37% increase in flow which does sound sizeable. Would it be similar to a water-hammer effect? I would think that with a lower psi switch the water would come on softer than a 45psi setting BUT would maintain better flow once the accumulator tank bleeds off its pressure. Does that make any sense? I know your known for your NASA analytical skills Gary.

 

[Four Suns]

No analysis here... you won't get water hammer stuff...

I went from 3.3 GPH pumps to 3.5 GPH pumps and had to increase the size of the expansion tank because of the surge problem... I have two pumps in parallel though. I'm just speaking from my experience.

 

[Skuza]

Hmmmm....
Hey on your parallel setup do both pumps run or do they stagger based on pressure or need?