Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 13 of 13

Thread: Pressure Question

  1. Back To Top    #1
    tagprod's Avatar
    Join Date
    Jul 2007
    Location
    Tomball, Texas
    Posts
    489

    Pressure Question

    When the main pump is running, the pressure gauge on my cartridge filter reads 20 PSI. When I switch to spa mode (also ran by the main pump) the PSI jumps to 29. I cleaned the filer, but I got the same results. Anyone know why?
    Brian
    20K IG Gunite w/ raised 7ft spillover spa. 1.5 HP Hayward Northstar pump 425 sq ft Hayward cartridge filter, Colorlogic lights AquaRite SWG AquaLogic PS-8 control
    1hp pump for sheer descent

  2. Back To Top    #2

    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    28,409
    tag,

    By switching to spa mode, you increase the resistance to waterflow on the pressure side of the system. When the resistance is increased, the pressure goes up.

    Conversely, you could restrict the suction side of the pump (not that you want to...in fact, you DON'T want to) and the pressure would go down.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3
    tagprod's Avatar
    Join Date
    Jul 2007
    Location
    Tomball, Texas
    Posts
    489
    Thanks Dave. By "resistance to waterflow" do you mean only drwaing water from the two main drains at the bottom of the spa in spa mode verses in pool mode where you have two skimmers 4 main drains and a suction side cleaner?
    Brian
    20K IG Gunite w/ raised 7ft spillover spa. 1.5 HP Hayward Northstar pump 425 sq ft Hayward cartridge filter, Colorlogic lights AquaRite SWG AquaLogic PS-8 control
    1hp pump for sheer descent

  4. Back To Top    #4

    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    28,409
    Those are all on the "suction" side of your pump. Resistance (friction) on the suction side decreases pressure on your guage.

    The increase in pressure you are seeing is because of the increase in friction on the "pressure" side of the system....basically from the pump impellor 'til the water gets back in your pool
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887
    This is normal. The effects Duraleigh is describing are to be expected in that situation.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  6. Back To Top    #6
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    9,918

    Re: Pressure Question

    Quote Originally Posted by tagprod
    When the main pump is running, the pressure gauge on my cartridge filter reads 20 PSI. When I switch to spa mode (also ran by the main pump) the PSI jumps to 29. I cleaned the filer, but I got the same results. Anyone know why?
    I don't want to be too alarming but a 9 PSI rise seems pretty large to me. That is over 20 feet of head! I would expect less than 4 PSI rise between a spa and pool but it depends on what the spa plumbing is. Has it always been like this?

    Could you describe your plumbing in a bit more detail?

    Pump model/HP
    Pipe size for pool and spa
    # pipe runs from pad to pool and spa
    # returns for pool and spa (i.e. jets or returns depending on what the filter pump drives for the spa mode)
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  7. Back To Top    #7
    tagprod's Avatar
    Join Date
    Jul 2007
    Location
    Tomball, Texas
    Posts
    489
    It's a Heyward 2HP Northstar. I'm not certain on the plumbing size.

    There are 5 returns for the pool and 6 jets on the spa.
    Pipe rune? I'm looking for a pic but I can't find one. Here is the Rebar stagewith the plumbing on the spa



    the equipment pad is much closer to the spa returns than some of the other returns. the little box connected to the left side of the house is the eq pad. The pool is 34 feet long for a point of reference

    Brian
    20K IG Gunite w/ raised 7ft spillover spa. 1.5 HP Hayward Northstar pump 425 sq ft Hayward cartridge filter, Colorlogic lights AquaRite SWG AquaLogic PS-8 control
    1hp pump for sheer descent

  8. Back To Top    #8
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    9,918
    Your signature says 1.5 HP but your post says 2 HP?

    Anyway, from your pictures, everything looks ok to me. The higher pressure is probably due to the type of jets you have in the spa. Some require pretty high pressure.

    If the jets feel pretty strong, then I would not worry about anything.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  9. Back To Top    #9
    tagprod's Avatar
    Join Date
    Jul 2007
    Location
    Tomball, Texas
    Posts
    489
    It's 2 hp - I thought it was 1.5 when I put the sig together. I'lll have to fix that. The jets are pretty strong. I never looked at the pressure gauge in spa mode - because I'm usually getting in and I thought it would be the same. As the pool pressure rises will the spa rise accordingly?
    Brian
    20K IG Gunite w/ raised 7ft spillover spa. 1.5 HP Hayward Northstar pump 425 sq ft Hayward cartridge filter, Colorlogic lights AquaRite SWG AquaLogic PS-8 control
    1hp pump for sheer descent

  10. Back To Top    #10
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887
    Yes, as the filter gets dirty the pressure in both pool and spa mode will rise.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  11. Back To Top    #11
    tagprod's Avatar
    Join Date
    Jul 2007
    Location
    Tomball, Texas
    Posts
    489
    not to keep asking dumb questions, but if the pool operates at 20PSI and the spa at 29 PSI can I still wait until the pool is at 28PSI before cleaning or should I clean it when the spa rises a couple of PSI higher say to 31? I don't have the literature in front of me, but I'll read that too tonight.
    Brian
    20K IG Gunite w/ raised 7ft spillover spa. 1.5 HP Hayward Northstar pump 425 sq ft Hayward cartridge filter, Colorlogic lights AquaRite SWG AquaLogic PS-8 control
    1hp pump for sheer descent

  12. Back To Top    #12
    divnkd101's Avatar
    Join Date
    Mar 2007
    Location
    Pearland, TX (Houston Suburb)
    Posts
    587
    Brian,

    I would stay focused on the pool mode pressure when determining when is the best time to clean your filter.
    MIKE

    21K Inground Custom w/ Spa (Gunite/Plaster), SWCG, Hayward Northstar, Polaris 280, Hayward Color Logics, Jandy PS-8

  13. Back To Top    #13
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887
    You want to clean/backwash when there is an 8 to 10 PSI increase in pressure in the same mode that you noted the starting pressure in. If you note the starting pressure in pool mode, then wait till you reach the increased pressure in pool mode.

    There is no such thing as a dump question. Asking questions is how we learn.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •