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Help me plumb a second fresh water pump.

Discussion in 'Technical Discussion' started by Prospective, Dec 21, 2016.

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  1. Prospective, Dec 21, 2016
    #1
    Prospective

    Prospective Senior Member

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    I've posted this on a couple of other forums and gotten some rather bizarre answers so it makes me think either I don't understand something obvious or I'm not asking the questions clearly. I don't think my proposed set-up is atypical so hoping you folks can help...

    I have an ac well pump for my fresh water. Works great but I don't like having to run genny to use it on hook etc. After some consideration I've decided I'd like to just plumb a traditional dc pump (shurflow etc.) parallel in line on its own breaker.

    I would tap the supply before the current pump and tap the outflow after the current pump and accumulator tank. My thought is accumulator would still pressurize and check valves on each pump should prevent back flow from one to another?? I would only have one on at a time (switched via main breakers) but if they were inadvertently both on and have the same 40psi pressure switch setting seems like they'd both shut off once system was pressurized? I realize I could put in shut-offs before and after each pump but don't see a need other than in the even I have to remove one pump for service while keeping the other in service. Mainly, I don't want to have to monkey with valves each time I change from one to the other pump.

    Wanted to see if anyone saw any potential problems before I go hacking into my water lines.
    Last edited by a moderator: Dec 21, 2016
  2. captainwjm, Dec 21, 2016
    #2
    captainwjm

    captainwjm Senior member

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    That was the sort of set up on my old Viking; The were just Tee-d off before the lines ran into the accumulator tank.
    The pressure on the AC well pump was higher than the DC Jabsco, so whenever the AC was on, the DC pump was off; and when the AC was off, the pressure dropped until the DC pump came on. Worked great.
  3. baltimore bob, Dec 21, 2016
    #3
    baltimore bob

    baltimore bob Member

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    Check valve on each pumps output. T them in. Job done.
  4. Capt J, Dec 21, 2016
    #4
    Capt J

    Capt J Senior Member

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    Yeah, you should be fine unless in the remote chance one of the checkvalves went bad (rare) or you took one down to change it. I'd prefer to T before the accumulator.
  5. DOCKMASTER, Dec 21, 2016
    #5
    DOCKMASTER

    DOCKMASTER Senior Member

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    I have the exact set-up you are describing. I have an ac powered shallow well type pump with pressure tank as primary. Then I have a back-up dc Shurflo pump. A simple 3-way valve to select if incoming water from potable tank goes into the main pump or the Shurflo. A check-valve on the outlet side of the Shurflo and into the main line. The dc pump also helps to prime the main pump if I ever run completely empty.
  6. Pascal, Dec 22, 2016
    #6
    Pascal

    Pascal Senior Member

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    Check valves as described above plus valves before and after each pump so you can work on one without shutting down the whole system
  7. Prospective, Dec 22, 2016
    #7
    Prospective

    Prospective Senior Member

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    Thanks everyone! I should have figured you guys would be more familiar with this set up. And I agree shut-offs before and after make sense to be able to service a pump. And to answer Capt J's question, I would prefer to Tee into the line before the accumulator as well but space and varying pipe sizes would create a mess of connections. Teeing in just after (about 12") the accumulator would create a much cleaner set-up so as long as it's not a deal breaker, I think that's the way to go.

    A follow up/clarification???

    Do I really need to install separate check valves after the pumps?? My thinking (and from my reading) is that any pump with an integral pressure switch would already have some kind of check valve or backflow preventer otherwise it would bring the system up to pressure, shut off, and then release the pressure back thru the pump. Am I wrong here???
  8. Capt J, Dec 22, 2016
    #8
    Capt J

    Capt J Senior Member

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    You should be fine plumbing it after the accumulator tank and it should still work I believe.

    It depends on the check valve of the pump, usually they're built in and you should be ok, but if you have a bad check valve in one pump and no manual shut off valves, then the redundant pump is useless.