Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 19 of 19

Thread: Vacuum Pressure and Filter Pressure

  1. Back To Top    #1

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Vacuum Pressure and Filter Pressure

    After reading some threads here I decided to take some pressure readings.
    Vacuum is 14" Hg (at pump drain) ~ 15.82 psi
    Filter Gage is 12 psi

    I have (2) 1-1/2" going into 3 way Jandy and 2" going into the pump
    1-1-2" going into the pool (3 eyeballs) Heater and filter is 2" in/out.

    How would I figure my head ??
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  2. Back To Top    #2

    Re: Vacuum Pressure and Filter Pressure

    14 inches of mercury is 6.876 psi or 15.86 feet of head. 12 psi = 27.68 feet of head. Your total head loss is 15.86 + 27.68 = 43.54 feet.

    You can add the height of the pressure gauge above the suction gauge for a more accurate number.

    What pump do you currently have?

  3. Back To Top    #3

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    No name on the pump, but motor is 1 hp. So total should be about 45 ft. is that good or bad
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  4. Back To Top    #4
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Vacuum Pressure and Filter Pressure

    45 feet is well within the normal range. How good or bad that is depends on what you are comparing to. That is perfectly fine for a random pool, not so good if you had an efficiency expert design everything.
    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

  5. Back To Top    #5

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    I have ordered (latest & greatest) new Pentair VS (8 speed). Any heads up ?
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  6. Back To Top    #6
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Vacuum Pressure and Filter Pressure

    That is a great pump. The main thing to keep in mind is that it is a fairly complex piece of technology. It will work right out of the box, but to take full advantage of it, you should plan on spending some time getting things optimized.
    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

  7. Back To Top    #7

    Re: Vacuum Pressure and Filter Pressure

    sukhbir, it's important to understand that that head loss is only for that flow rate. Every flow rate will generate a different head loss. If you plot these numbers, you will create a "System Curve".

    A system curve is like a pump curve. To get your system curve, you would use different flow rates and note the vacuum and pressure.

  8. Back To Top    #8

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    Here is my plan
    Hook up the vacuum gauge to pump.
    Clean the filter.
    run pump and record rpm,filter pressure, vacuum, watts
    rpm will be 3450,3000,2800,2400,2000,1600,1200,800, and lower if worked
    and post them here. How can I figure the GPM ?
    Anything else I should do ?
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  9. Back To Top    #9
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,489

    Re: Vacuum Pressure and Filter Pressure

    You can use the GPM Estimate spreadsheet in this link.

    But for most plumbing, if you have the flow rate at one speed you can just scale the flow rate by RPM.

    GPM New = GPM Old * RPM New / RPM Old

    However, check valves can through this off some.

    The problem with measuring pressure and vacuum at low speeds is the resolution is not very good so the measurement error is high. So you are better off calibrating at high speed and scaling for lower speeds.
    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

  10. Back To Top    #10

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    Thanks Mark will do
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  11. Back To Top    #11
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,489

    Re: Vacuum Pressure and Filter Pressure

    I just uploaded a new version which can be calibrated with your pressure and vacuum measurements at high speed. The tab is called Head2GPM.
    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

  12. Back To Top    #12

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    Just Did. and #s are really close what I am expecting. Now let's see how the real life looks like. Thanks again Mark
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  13. Back To Top    #13

    Re: Vacuum Pressure and Filter Pressure

    You could use a flowmeter to measure the flow rate.

    That pump might be too much for your system at high speed, so be careful at the higher speeds.

  14. Back To Top    #14

    In the Industry

    Join Date
    Mar 2011
    Posts
    441

    Re: Vacuum Pressure and Filter Pressure

    Quote Originally Posted by sukhbir
    No name on the pump, but motor is 1 hp. So total should be about 45 ft. is that good or bad

    45' seems reasonable, but 14" HG seems high.

    Typically on design we want no more than 10" HG max ~5" or less is ideal.
    20X40 30,000 gallon gunite pool

  15. Back To Top    #15

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    This pool was built in 1983. One skimmer one main drain. both 1.5 dia into Jandy and 2" going into pump. 2" tee and 2 " from Spa. After heater 2" into spa and 1.5" to pool (3) 1" eye balls. ABout 70 ft from main drain and 36 ft from skimmer. about 1.5 ft above water level.
    @racket Can I do something cheap to improve suction ?
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  16. Back To Top    #16
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,489

    Re: Vacuum Pressure and Filter Pressure

    For dual 1.5" lines, that does seem a little high. What is your current pump? Are you sure both lines are clear and the valve is set to draw from both?
    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

  17. Back To Top    #17

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    No name on the pump but motor is 1 hp. Can't tell if both are fully open or not. Right now the way 3 way Jendy is plumbed is 2" from spa and 1.5" from skimmer and 2" going to pump. Main drain is plumbed into 2" to pump with a 2x2x1.5 tee. I can not control flow between skimmer/main drain. Main drain may be clogged. This pool was built in 1983.

    My new plumbing plan is
    skimmer(1.5") and main drain (1.5") into Jendy and 2" to the pump. Tee of the 2" to pump to 2x2x2 with 2 way jendy from spa. Replacing tees to 45 hope that will help the suction head and I will have more control over skimmer/Maindrain.
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

  18. Back To Top    #18
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,489

    Re: Vacuum Pressure and Filter Pressure

    If you are planning to cut into the lines, that would be a good time to use a drain king to flush the lines out and check for any clogs. Also, if you are replacing a 90 with 2 45's that may actually increase your head loss and decrease it so I wouldn't bother with that.
    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

  19. Back To Top    #19

    Join Date
    Apr 2011
    Location
    Fresno, California
    Posts
    46

    Re: Vacuum Pressure and Filter Pressure

    Thanks Mark.
    23k IG. Plaster. StaRite system 3 Cartridge Filter (S7M120), Pentair MiniMaxNT Heater. IntelliFlo VS (8 Speed). Going BBB

Posting Permissions

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