Potable water pump plumbing

[dar636]

So I have a couple of questions. This is how the water system has been plumbed since I have had the boat. I've only been using the 32v pump as the 120v was leaking out of the diaphragm when I took the boat. I replaced the 120v pump and it immediately blew out and leaked again from the diaphragm I think from back pressure when the 32v pump operates.

I think that to be able to use the pumps as plumbed there needs to be a check valve in the outlet of each pump so that when the other operates pressure does not go back into the non-running pump, which in the case of the 120v pump seems to be fatal.

The yellow highlighted pic shows the system with the 'Y' valves positioned for operating the 32v pump.

The blue highlighted pic shows the flow when the 120v pump would run BUT the 'Y' vales aren't positioned... its the only pic I had.

First question is how am I supposed to be using the system? Manually turn on whatever pump I intend to use and position the valves accordingly?

Or leave them both ON and whichever one has power would run? How would I position the 'Y' valves? Manually again?

Frankly I could probably live without the 120v pump as the 32v works well enough including deck washing.

Any comments or suggestions? Thanks-

 

[SKYCHENEY]

I have check valves on both of my pumps.

 

[dar636]

PS: I do have each pump on its own breaker in the power panels.

 

[Captain Ralph]

The 120Vac jet pump is an over kill. However, it should be able to hold any pressures fine.
Most jet pumps like this already have a check valve installed internally.
Just by their nature, DCv pumps are nothing but 3 or 4 check valves in series.
So, I have to ask, What kind of wild pressures are you developing to blow out a jet pump?

 

[Captain Ralph]

We have a 32Vdc FloJet pump that works very well.
Only so much water can flow thru our 3/8" copper lines, no matter how large of a pump you install.

 

[dar636]

I don't have a pressure gauge to monitor the outlet pressures with the DC pump, I'd guess its fairly low though, 10 PSI? The 120v pump both times it failed leaked at the diaphragm cover as marked. Water just pours out like the diaphragm ruptured from having pressure on the wrong side. I have no idea if there is an internal check valve.

The more I think about it I am leaning towards getting rid of the 120v pump entirely. It would certainly simplify that corner of the engine room.

Though if I keep both pumps I'd put check valves where noted?