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Thread: Pump issue / replacement

  1. Back To Top    #1

    Join Date
    Aug 2009
    Novato, CA

    Pump issue / replacement

    I moved to a house with the below-detailed pool/spa combo about two years ago. Thanks to this great website, care and maintenance using the BBB method has worked beautifully.

    The pool/spa were built in 1978. They have completely separate plumbing. Both need to be resurfaced and have tiles coming lose, but neither appears to leak water yet. The pool gets very little use (less than 15 total days last year), but the spa is used regularly.

    Recently, the spa pump started sucking air from somewhere that ends up displacing the water in the filter. I tried resealing and replacing the gasket on the pump basket, to no avail. This problem just started in the last few weeks. I bought a vacuum gauge and gathered some detailed system information, presented below. Pictures of the spa pump are attached. I have other pictures available if the textual description isn’t clear enough.

    After the system information are some of my ideas. I’m looking for any helpful comments/suggestions.


    15000 gallons
    1.5” suction line fed by the main drain and the skimmer
    1.5” return line feeding 3 jets

    New-ish Pentair Pinnacle pump: 1hp * 1.25sf = 1.25 sfhp
    New (last year) Sta-Rite System2 PLM300 cartridge filter

    50 feet from pad to far end of pool

    Vacuum at pump basket is 21 inHg (edit: why is this so high, resulting in higher suction head than return head?)
    Pressure at clean filter is 7 psi
    Total dynamic head (2.31*7+3)+(1.13*21) = 42.9 feet

    Pump currently runs 3.5 hours/day in winter and 5 hours/day in summer. Due to topography, the pool loses all sun at 2pm in summer and gets no sun in winter, resulting in maximum summer water temp of about 78F and minimum winter temp of about 52F.


    Old Jandy RayVac (no longer made) powered by dedicated pump tee-d into the pool return line
    MagneTek Century Centurion pump motor: 0.75hp * 1.5sf = 1.125 sfhp
    3/4” hoses at this pump connected to 1” PVC pipes for inlet/outlet

    Pump currently runs 1.5 hours a day.


    600 gallons
    2” suction line fed by the main drain
    1.5” return line feeding 3 jets
    Passive air system, controlled by a valve, and powered (I assume) by a venturi in the return line to the jets

    Old pump with metal basket housing – says “Premier” on the side
    Old Century pump motor: 2.0hp * 1.2sf = 2.4 sfhp
    Old Sta-Rite Posi-Flo 100TX cartridge filter

    30 feet from pad to spa
    Vacuum at pump basket = 2 inHg (edit: this seems low, but it's in-line with the estimator equation on this forum)
    Pressure at clean filter = 10 psi
    Total dynamic head (2.31*10+3)+(1.13*2) = 28.36 feet

    Old Teledyne Laars EPC-175 175,000 btu gas heater


    I have several solutions in mind. I’m not looking to spend a ton of money to get the slickest gadgets because I’m not sure if our future plans will involve resurfacing the pool or filling it in and getting a much more energy-efficient above-ground spa. Currently the spa takes several hours to heat up with that old gas heater, so using it takes a bit of prior planning. A new energy-efficient spa that is always hot would be much more useable for us. Anyway, here are my ideas:

    1. Re-do the PVC plumbing on the intake side of the spa pump, keeping the same old pump in place. This pump seems oversized for only 3 jets and I doubt the leak is in the PVC anyway, so this might be a waste of time.

    2. Get a new pump for the spa that is sized more appropriately for this installation. The current pump seems oversized for only 3 jets and 1.5” pipe.

    3. Move the current pool pump to the spa and get a new pump for the pool that is sized more appropriately for this installation. The current pool pump seems oversized for 3 return jets and 1.5” pipe. Edit: Is it because this pump is oversized for the pool that the suction head is so high?

    Options 2&3 would both save energy and could probably be done for less that $500. #3 is obviously more work than #2, but it might be better energy-wise to downsize the pool pump since it runs the most.

    Any thoughts or opinions from the experts? If I go with #3 above, is it worth buying a 2-speed pump for the pool considering it never gets used and the water temp and sun situation allow me to run the pump for so little time anyway?

    Thanks in advance. If you agree that a new pump is in order, can you suggest a specific size? I think I know what’s needed based on all the valuable information on this website, but confirmation would be nice.

  2. Back To Top    #2

    In the Industry

    Join Date
    Jan 2011

    Re: Pump issue / replacement

    That's an old aquaflow pump...

  3. Back To Top    #3

    Join Date
    Aug 2009
    Novato, CA

    Re: Pump issue / replacement

    Here's an additional question I didn't think of in the first post..

    Assuming I move the pool pump to the spa and buy a new pool pump..

    Will a 1/2 hp single-speed pump or a 1 hp two-speed pump running at low speed create a problem with the sweeper, even though it has its own booster pump?


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