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Thread: These numbers seem low with a Pentair VS Pump

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    These numbers seem low with a Pentair VS Pump

    I just got all new equipment and I have an inground pool/spa combo with shared equipment. The pool is about 40K gallons and spa about 1200 gallons. The pool has one main drain and the 2 skimmers are plugged (capped off) as somewhere they are leaking so we just plugged them as we have a cover so don't need much skimming anyhow.

    Question is, I need a flow of at least 30 GPM if I run 24hrs/day to do a full circulation of the pool/spa water.

    Well, the pump needs to run at about 2300rpm to get there so it doesn't seem to save any on electricity over a standard pump....... I can't lower the rpm ever as I would not be able to filter all the water once a day.......

    Can anyone explain?


    Here are some specs when testing RPM/ Watts/ GPM
    2000 RPM-----22GPM----474 Watts
    2100 RPM-----25GPM----537 Watts
    2340 RPM-----35GPM----723 Watts
    2500 RPM-----37GPM----846 Watts
    3000 RPM-----45GPM----1437 Watts
    3250 RPM-----52GPM----1829 Watts
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

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    mas985's Avatar
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    Re: These numbers seem low with a Pentair VS Pump

    Those numbers would be consistent with very high head loss plumbing. What filter pressure are you reading at 3250 RPM? With 3250 RPM, 52 GPM & 1829 watts you may have a head loss of close to 80'.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  3. Back To Top    #3

    Re: These numbers seem low with a Pentair VS Pump

    Part of the problem is that the skimmers are plugged. With only the main drain, you are going to have problems.

    What size pipe is the plumbing from the main drain to the pump, and how far is it? What size are the returns, and how many are there?

  4. Back To Top    #4

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by mas985
    Those numbers would be consistent with very high head loss plumbing. What filter pressure are you reading at 3250 RPM? With 3250 RPM, 52 GPM & 1829 watts you may have a head loss of close to 80'.

    Looks like filter pressure reads 30 PSI and a different pressure gauge near heater reads 10 PSI.
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  5. Back To Top    #5

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by JamesW
    Part of the problem is that the skimmers are plugged. With only the main drain, you are going to have problems.

    What size pipe is the plumbing from the main drain to the pump, and how far is it? What size are the returns, and how many are there?

    Do skimmers add gpm......?? I switched over the all spa where it too has one skimmer and one main drain and pressures didn't change much at all and that is a lot closer to equipment than the pool.....?


    The piping is 2" and the distance would be approx. 40'-70' depending if things are run at an angle under pool or go out and over...... directly to equipment room.

    I am not sure on returns..... I think everything is 2".
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  6. Back To Top    #6

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by zmock8
    I just got all new equipment and I have an inground pool/spa combo with shared equipment. The pool is about 40K gallons and spa about 1200 gallons. The pool has one main drain and the 2 skimmers are plugged (capped off) as somewhere they are leaking so we just plugged them as we have a cover so don't need much skimming anyhow.

    Question is, I need a flow of at least 30 GPM if I run 24hrs/day to do a full circulation of the pool/spa water.

    Well, the pump needs to run at about 2300rpm to get there so it doesn't seem to save any on electricity over a standard pump....... I can't lower the rpm ever as I would not be able to filter all the water once a day.......

    Can anyone explain?


    Here are some specs when testing RPM/ Watts/ GPM
    2000 RPM-----22GPM----474 Watts
    2100 RPM-----25GPM----537 Watts
    2340 RPM-----35GPM----723 Watts
    2500 RPM-----37GPM----846 Watts
    3000 RPM-----45GPM----1437 Watts
    3250 RPM-----52GPM----1829 Watts
    i have the Pentair VF pump

    1100 RPM------25GPM-----154 Watts

    to get the same 25 GPM your pump needs to run at 2100 RPM's and use 537 Watts u must have some major head loss

  7. Back To Top    #7

    Re: These numbers seem low with a Pentair VS Pump

    little tiny filter?

  8. Back To Top    #8

    Re: These numbers seem low with a Pentair VS Pump

    30 psi indicates excessive head loss on the pressure side. 30 psi is about 70 feet of head just on the pressure side, and the suction side is going to add at least 10 feet more for a total of over 80 feet of head.

    Are you sure that the gauge is good? Does it go to zero when the pump is off? If the gauge is good, then there is something causing the flow to be restricted.

    Regarding the suction: Ideally, you don't want more than about 65 GPM on a single 2-inch PVC pipe on the suction side for up to a total pipe length of about 100 feet. Only using the main drain is not an ideal situation. It's not as safe as having the skimmers, and if there is a hydrostat, it might get pulled up and cause a leak if the main drains get blocked.

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    Re: These numbers seem low with a Pentair VS Pump

    Can you explain exactly what head loss means in layman terms........?? Is it something that is or can be fixed or no....??

    I can't be for sure the gauge is good but it is brand new and just installed..... It is a Blue White Gauge and goes on after the filter.. I haven't checked if it goes to zero when it is off.. What could be causing the flow to be restricted....?? I will backflush filter tomorrow and make sure we are good there and go from there. It has been a few days (5) since backwash has been done and the pool is freshly refinished and rehabbed.

    And can someone answer if the skimmers were operational, would that raise the flow more.....? I was just told that I didn't really need the skimmers that bad as I have a cover on all the time and all I would need to do is physically filter anything that gets on top rather than having it skim..

    And the sand filter is the biggest size 100D.
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  10. Back To Top    #10

    Re: These numbers seem low with a Pentair VS Pump

    Head loss means the amount of resistance to water flow. The more resistance, the more pressure it takes to move the water through the system at the same flow rate.

    If you just did a full renovation, then I would think that the builder would have wanted to get the skimmers working. All pools are built with skimmers, because skimmers are important. I think that the skimmers should be working. Although, right now, the pressure side is causing the flow problems.

    If this is new plaster, then I would suspect calcium scale as one of the possible reasons for flow restriction.

    It's also possible that some of the valves or equipment are installed incorrectly, or not adjusted right.

    Is the builder helping with these issues?

    Can you post a picture of the equipment?

  11. Back To Top    #11

    Re: These numbers seem low with a Pentair VS Pump

    Yes, I opted to not dig up skimmers as I figured with a cover on majority of time, I didn't need them...... And I do have one skimmer working in spa and obviously both main drains.

    How can you tell pressure side is causing problems......?? Why couldn't it be not enough water coming into system? Where do you get calcium scale to slow flow rate?

    Yes, pool company is helping with this issue.
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  12. Back To Top    #12

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by mas985
    Those numbers would be consistent with very high head loss plumbing. What filter pressure are you reading at 3250 RPM? With 3250 RPM, 52 GPM & 1829 watts you may have a head loss of close to 80'.


    Is 3250 the rpm in which you are to test filter PSI?
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  13. Back To Top    #13
    JasonLion's Avatar
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    Re: These numbers seem low with a Pentair VS Pump

    If there was a problem on the suction side the filter pressure would be lower. High filter pressure suggests a problem on the pressure side.
    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

  14. Back To Top    #14

    Re: These numbers seem low with a Pentair VS Pump

    Looks like I only have 2 returns to the pool and they are pretty small..... So I guess i could have a new line run in addition to the 2 already there...... I am also going to have the pool company swap out the VS to a VF so I can get an accurate flow meter rate.... Someone looked at the flow meter that was installed today and it wasnt perfectly perpendicular with pipe and they said that could affect the reading.

    I also can open the bipass valve more so it will feed the spa a little more as long as it doesn't overflow. The spa and pool have an equalizer line in them connecting them.

    Not sure how much it matters but the pool is 9 feet deep at deep end and the bottom of equipment room is probably level with the bottom of pool so I imagine we get some loss with the pool equipment having to push a little harder to get into pool...??
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  15. Back To Top    #15
    mas985's Avatar
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    Re: These numbers seem low with a Pentair VS Pump

    Having the equipment 9 feet lower than the pool surface will make the filter pressure about 4 PSI higher than if it was at the pool surface. The static head nets out because the suction side sees a static head gain of 9' while the return sees a static head loss of 9'.

    I would like to understand this statement:
    Looks like filter pressure reads 30 PSI and a different pressure gauge near heater reads 10 PSI.
    What was the RPM and is the filter and heater at different elevations?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  16. Back To Top    #16

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by zmock8
    Where do you get calcium scale to slow flow rate?
    If this is a new plaster, then it will create a lot of calcium hydroxide, which can become a lot of calcium carbonate if the pH is not kept low enough. If you can post a full set of readings including the :

    pH
    TA
    Calcium hardness
    Cyanuric acid
    Salt
    Temperature

    That would help determine the risk of scaling. I'm thinking that the heaters or other equipment might be scaled.

  17. Back To Top    #17

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by mas985
    Having the equipment 9 feet lower than the pool surface will make the filter pressure about 4 PSI higher than if it was at the pool surface. The static head nets out because the suction side sees a static head gain of 9' while the return sees a static head loss of 9'.

    I would like to understand this statement:
    Looks like filter pressure reads 30 PSI and a different pressure gauge near heater reads 10 PSI.
    What was the RPM and is the filter and heater at different elevations?

    So I just ran it and 2200 RPM was about 35gpm 15 PSI at filter and 6 PSI right before it goes into the ground back to returns.....

    At 3250 RPM, the filter PSI was 29 PSI and the return PSI was 10 PSI.
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  18. Back To Top    #18

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by JamesW
    Quote Originally Posted by zmock8
    Where do you get calcium scale to slow flow rate?
    If this is a new plaster, then it will create a lot of calcium hydroxide, which can become a lot of calcium carbonate if the pH is not kept low enough. If you can post a full set of readings including the :

    pH
    TA
    Calcium hardness
    Cyanuric acid
    Salt
    Temperature

    That would help determine the risk of scaling. I'm thinking that the heaters or other equipment might be scaled.


    It is pebbletech and the equipment is brand new..... Does scaling happen right away to brand new equipment..??
    40K Gallon Pool w 1200 Gal Spa on shared equipment, Delta UV System, Raypak Propane 400K BTU Heater, Pentair 120K Heat Pump, Tagelus Sand Filter, 2 x Pentair Intelliflo VS Pumps--- 1 for Main pump and one for spa jets, Booster/ Cleaner Pump

  19. Back To Top    #19

    Re: These numbers seem low with a Pentair VS Pump

    Quote Originally Posted by zmock8
    It is pebbletech and the equipment is brand new..... Does scaling happen right away to brand new equipment..??
    It can if the chemistry is off, and if plaster dust gets in the equipment. Since you're only using the main drain, that increases the likelihood of getting a lot of plaster dust into the equipment.

    cavitation-when-my-heater-starts-t30011.html

    Also, if the heaters are 9 feet below the water's surface, then you need to replace the pressure switches with flow switches or they might run with too little flow and become damaged. They could even run with no flow.

    Excessive heating of the water in the heaters would greatly increase the risk of calcium scaling.

  20. Back To Top    #20
    mas985's Avatar
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    Re: These numbers seem low with a Pentair VS Pump

    At 3250 RPM, the filter PSI was 29 PSI and the return PSI was 10 PSI.
    So what equipment/plumbing is between the 29 PSI and the 10 PSI measurement.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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