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Thread: Low speed = No PSI on filter

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    Low speed = No PSI on filter

    When I run my pump at 1000 RPM, the filter reads 0 PSI even though my flow meter shows water moving at about 15 GPM. At 2000 RPM the needle moves up to 5 PSI (35 GPM). At 3450 RPM it was 20 PSI last time I cleaned the filter ; today it's 24 PSI. I don't ever see an increase in PSI at the lower RPM's; I need to ramp the speed up to maximum in order to gauge when I will need to clean the filter again. Does this sound like normal operation and is there any disadvantage to running the filter at 0 PSI? For reference, I've had the gauge replaced 3 times.. behavior was the same on the previous ones.
    14K Freeform Gunite w/60% Blue Quartz plaster, Quad DE filter, Intelliflo VS Pump + Booster for Cleaner, Aquacal Heat Pump

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    Richard320's Avatar
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    Re: Low speed = No PSI on filter

    Normal.
    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!

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    JasonLion's Avatar
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    Re: Low speed = No PSI on filter

    It isn't really 0 PSI, the gauge just isn't very good. Pool equipment uses inexpensive and fairly low quality gauges when often have problems reading low PSI values. This isn't really a problem, you just need to use a fairly high RPM, the same one each time, to decide if it is time to clean the filter or not.
    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

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    mas985's Avatar
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    Re: Low speed = No PSI on filter

    Even the better gauges don't read well below 2 PSI. Take a look at the gauge that Dave sells and there are two missing marks between 0 and 2 PSI so the first increment is really 1.5 PSI. Most gauges skip at least the 1 PSI marker so zero is really 1 PSI. That is just where they put the needle stop so they call it zero. Also, most gauges have at least 1 PSI error.



    One easy way to tell if there is pressure in the filter is to open the filter purge valve and see if air or water comes out.
    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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    Re: Low speed = No PSI on filter

    Thank you all. Just wanted to make sure there were no contraindications there.
    14K Freeform Gunite w/60% Blue Quartz plaster, Quad DE filter, Intelliflo VS Pump + Booster for Cleaner, Aquacal Heat Pump

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    Divin Dave's Avatar
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    Re: Low speed = No PSI on filter

    You're good. The bigger the filter like you have, the lower the pressure will be and the lower the RPM then obvously the pressure will be lower.
    Combine the two, and you will prolly not have to clean your filter for a good while!

    I have a big cartridge filter and intelliflo, and I have to get the RPM up to about 1300ish before i even see the needle move at all.
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
    www.tftestkits.net Experience- it's what's learned just after you needed it most !!

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    H-12 1/2 Mike's Avatar
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    Re: Low speed = No PSI on filter

    What rpm do you recommend in the off season? I am currently running 2000 for 8 hours for a 16,400 gal gunite. The water temp is 53 degrees.
    16,400 gallon
    Cartridge Filter
    IG
    Plaster
    Intelli-Flo @ 2000rpm

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    mas985's Avatar
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    Re: Low speed = No PSI on filter

    2000 RPM for 8 hours is probably much too fast and much too long unless you have some specific reason for doing that. 1000 RPM is the most efficient speed but does not always work well for skimmers and cleaners (non-booster). General rule of thumb is set run time as short as possible because after chlorination, the only reason to run a pump is to keep debris out of the water and that is basically personal preference.
    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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    Richard320's Avatar
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    Re: Low speed = No PSI on filter

    I was going to say that. Way overkill on how long it's running. I have a single speed pump and my pool - same size - does just fine on about 2 hours a day this time of year. Even in the summer, 4 hours is plenty for me. You're just going to have to experiment as explained in pool school.
    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!

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