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Thread: Question about calculating pump run time.

  1. Back To Top    #1

    Join Date
    Jul 2010
    Location
    Philadelphia
    Posts
    134

    Question about calculating pump run time.

    I never paid much attention to run time but I would like to.

    I have a sta-rite filter, system:3 S8D110. It does not seem to be variable speed.

    Looking on the filter, it shows a max flow rate of 106 Gal/min and a filtration area of 53 sqft for a filtration rate of 2 gpm/sqft. I assume flow rate is based on freshly backwashed and charged filter.

    I have a 19,000 gal pool. Based on just the flow rate, that would be 3 hours to run through all my water once.

    The run time will also depend on my heating needs and how much I want to rely on my SWG. Having said that, based on flow rate alone even 9 hours is enough to filter the pool 3x (!) - but I wanted to check in here and see if those other filter parameters might change this assumption.

    Thank you!
    19000 gal in ground, pebble tec. Sta-rite system 3 DE filter, Aquarite SWG, raypak 406A heater

  2. Back To Top    #2

    Join Date
    May 2015
    Location
    Quebec, QC
    Posts
    35

    Re: Question about calculating pump run time.

    If heat distribution is important to you, you should run it during sun exposure. I run mine for only six hours with a replacement occurring every 2.5 hours. If I really want sparkling water, I have to run it 9 hours, which I do manually twice a week or so. If you are using a floating solar cover, you have to extend the run time, because surface water circulation is reduced as well as scouring in pool corners or pool floor at the deep end. I have to remove mine every 48 hours or so, to minimize biofilm formation, scrub and allow for longer filtration times.
    14 x 28 Jacuzzi vinyl inground pool, Jacuzzi Laser 250 sand filter, Hayward 1 HP pump.

  3. Back To Top    #3
    Richard320's Avatar
    Join Date
    Jan 2010
    Location
    San Dimas, CA (LA County)
    Posts
    18,768

    Re: Question about calculating pump run time.

    I get by with 3 hours a day. However, I don't run a SWG. You need to run it long enough with the SWG on to generate enough FC and keep the water clear.

    If you maintain FC no problem with SWG on 20% for 9 hours, then you could try SWG on 60% for 3 hours. Or some other multiple; whatever your setting are. Just experiment and run things the minimum amount you can and maintain the sparkle. It will save electricity. $$$$

    Pool School - Determine Pump Run Time
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

  4. Back To Top    #4

    Join Date
    Jun 2014
    Location
    Chandler/AZ
    Posts
    51

    Re: Question about calculating pump run time.

    To calculate the flow rate with any degree of accuracy you'll need to calculate the headloss. Using headloss along with the flow table for your pump, you can estimate the actual flow for your particular application.

    Headloss is also called back pressure. It's the resistance to flow that your pump must overcome. It's a combination of the losses on both suction and pressure side of system (from filter, pipe size, pipe length, elevation rise/fall, number of elbows, etc). The good news is that's it's easy to determine if you have a pressure gage.

    The pressure side is generally easiest...it's just the PSI on your filter x 2.31 to convert from psi to Feet of Head.

    Next, determine the inlet resistance. This will require a vacuum gage attached at the pump inlet side. Most pumps have a drain plug which can be used to connect the gage. Take this value (in psi) x 1.13 to get the suction losses in feet of head. If you don't have a vacuum gage, you can estimate suction loss as 1/3 of pressure loss.


    Add these two values to get the total headloss. Use this number in combination with the flow charts for your specific pump to determine the flow rate for your system.

    Your SWG should have a rating for how much Cl is generated in some given amount of time. It's been a long time since I've worked with heat exchangers, so someone else will have to chime in on that info, but this should get you a reasonable value for flow rate.
    15k Pebble Tec (2002), Ecomatic ESC-16 SWG
    Pentair Clean & Clear Plus Cartridge Filter Model CC420P (150GPM/420sqft/50psi)
    Pentair WhisperFlo Pumps x3, AO Smith 1 HP single-speed motors x3,
    Paramount IFCS, Taylor K-2006 Test Kit w/SpeedStir.

  5. Back To Top    #5

    Join Date
    Jul 2015
    Location
    Pasadena, CA
    Posts
    9

    Re: Question about calculating pump run time.

    Hi, am new to the forum and was just searching the swg thread about run time. 2 weeks ago I successfully completed an AA treatment for stains and pool looks like new but am concerned about too much chlorine and ph rise causing stains to return. About 3 weeks before the AA treatment, I had the variable pump installed; immediate savings but the salt cell died. So I just installed a new 1400 with sensor and dc and all is working fine. With my hi CYA and CH, any suggestions on run time to at least minimize the chlorine I am still going to be adding? Richard, I see you are in San Dimas, I'm in Pasadena so you know how crazy SCE is with the tiered pricing. I would like the swg to run at the low rpm setting in the day but the swg may not have enough flow. The variable has an rpm setting but I have noway to figure out flow rate as I had some awareness of what BassTrix is saying about back pressure and headloss. Do I just play with the settings on the pump to see at what point it shows no flow? That's what I am thinking and if so, trial and error it will be. btw, 47% water change not an option per wife instruction....

    cl. 10-15 (I am still having loss from the AA I think so trying to keep it between here; doing overnight test with new cell tonight)
    fc <.5
    ph 7.2
    TA 110
    CYA 150 using 1/2 pool 1/2 tap water method
    CH 600 probably more b/c i stopped adding drops
    3200 salt is pretty constant
    20k gal 14 x 40 gunite, raised spa with spillway, Pentair Intelliflo Variable Speed Pump
    Hayward pro grid DE, Raypak RP 2100 heater
    Purelink swg salt cell & Aqualink RS one touch control
    Barracuda G3 pool sweep, Taylor K-2006 test kit
    "The bigger the hammer, the smaller the brain!"

  6. Back To Top    #6

    Join Date
    Jun 2014
    Location
    Chandler/AZ
    Posts
    51

    Re: Question about calculating pump run time.

    Nesto, your pump should have a table with various curves for different pump RPM. As long as you can set the RPM, you should be able to dial in the flow you want.
    15k Pebble Tec (2002), Ecomatic ESC-16 SWG
    Pentair Clean & Clear Plus Cartridge Filter Model CC420P (150GPM/420sqft/50psi)
    Pentair WhisperFlo Pumps x3, AO Smith 1 HP single-speed motors x3,
    Paramount IFCS, Taylor K-2006 Test Kit w/SpeedStir.

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