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Thread: Pressure rise on a cartridge filter

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    Pressure rise on a cartridge filter

    I have a 15k IG pool with a pent air 420 cartridge filter and a pent air 1hp pump. the normal pressure was about 5-7. this past year the pressure rose @ 25-30 and the circulation decreased. I cleaned tha filters which broght the pressure down to normal levels, but within the week the pressure rose the chemicals were good and the pool looked good. I bought new filters. everything was fine for the first 3 weeks then the pressure rose again 10- 15. I cleaned the filters again and with the sasme results. I feel I'm cleaning the filters to often. when the pool was new 4 yrs ago i only had to clean the filters once a season. any help would be great.
    20 x 45 Inground vinyl, ~34,500 gallons,
    4 returns, 2 skimmers, dual main drain
    Pentair EasyTouch 4, IC40 SWG, MiniMaxNT 400, TR100 sand filter,
    Whisperflo .34/2 hp 2 speed, Polaris 280 w/ polaris booster pump,
    Wild ride slide, InterFab techni spring base w/ 8' InterFab olympian board
    APC 365 dark gray auto cover

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    Welcome to the forum. It sounds like you have organics in the pool. That's just a guess without test results but that description is sure indicative of an algae bloom, visisble or not, that is being partially killed and the dead algae is accumulating in your filter.

    Again, the only way to be sure is to post some test results. If you have observed increased chlorine consumption this summer that would point at the same culprit.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3
    Thanks for the response. would a water sample brought to the local pool supply store do the trick. ?
    20 x 45 Inground vinyl, ~34,500 gallons,
    4 returns, 2 skimmers, dual main drain
    Pentair EasyTouch 4, IC40 SWG, MiniMaxNT 400, TR100 sand filter,
    Whisperflo .34/2 hp 2 speed, Polaris 280 w/ polaris booster pump,
    Wild ride slide, InterFab techni spring base w/ 8' InterFab olympian board
    APC 365 dark gray auto cover

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    It will be helpful to get your water tested but it will be an inference of algae rather than being able to test for algae......they won't do that.

    So, if you get it tested, I suspect you will find your Chlorine is low, allowing algae to get a foothold. However, you may have recently upped the Chlorine but not enough to kill the algae. You probably need to shock your pool. How are you currently chlorinating? Post that back and any recent additions of chlorine you have made and we'll get you started. Also let us know where you live to get an idea of your pool temp and if you'll be winterizing.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5
    We chlorinate with a floatting chlorinator which goes through @ 3 3" tabs a week. we add chlorine when ever its low. we test the water with test strips. I live it CA. Modesto area. the central valley.
    20 x 45 Inground vinyl, ~34,500 gallons,
    4 returns, 2 skimmers, dual main drain
    Pentair EasyTouch 4, IC40 SWG, MiniMaxNT 400, TR100 sand filter,
    Whisperflo .34/2 hp 2 speed, Polaris 280 w/ polaris booster pump,
    Wild ride slide, InterFab techni spring base w/ 8' InterFab olympian board
    APC 365 dark gray auto cover

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    Yeah, I think it's time for a pool store test or a good drops-based test kit.

    The strips are notorious for giving inaccurate results and, since you've been using pucks, you may have some pH issues and CYA problems as well. Please don't consider this as a solicitation but doing your own testing with a good kit will provide you far more info and help in keeping your pool crystal clear......Your own testing with a good drops-based kit is generally more accurate than even the pool store tests.

    So, how does your water look? Is it sparklingly crystal or do you think it may be just a little duller than last year? If it's a little dull that may be an indication of algae as well. Post up some test results from the pool store (be sure to include CYA (stabilizer) results as well as pH, chlorine, alkalinity and calcium.

    I know you only asked about cleaning your filter less often but everything you've said to this point leads me to believe you have some algae developing. The test results will tell us how high to bring your chlorine to cure the problem.

    Sounds like you probably do not winterize your pool so now would be a good time to fix the problem.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  7. Back To Top    #7
    Thanks for the help. I'll get that water test and get back to you.
    20 x 45 Inground vinyl, ~34,500 gallons,
    4 returns, 2 skimmers, dual main drain
    Pentair EasyTouch 4, IC40 SWG, MiniMaxNT 400, TR100 sand filter,
    Whisperflo .34/2 hp 2 speed, Polaris 280 w/ polaris booster pump,
    Wild ride slide, InterFab techni spring base w/ 8' InterFab olympian board
    APC 365 dark gray auto cover

  8. Back To Top    #8

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    Quote Originally Posted by riffin
    We chlorinate with a floatting chlorinator which goes through @ 3 3" tabs a week. we add chlorine when ever its low. we test the water with test strips. I live it CA. Modesto area. the central valley.
    In your 15,000 gallon pool, 3 3" Trichlor tabs/pucks (assuming 8-ounce weight pucks) would add 11 ppm to Free Chlorine (FC) and 6.7 ppm to Cyanuric Acid (CYA). With a cartridge filter, you don't backwash, so with minimal splash-out one summer season of 6 months would increase CYA levels by 174 ppm. Unless you changed the water over the years or diluted with winter rains, your CYA level is probably through the roof and makes your chlorine very ineffective. At 174 ppm CYA you would have to have an FC level of 13 ppm to prevent algae growth.

    So I agree with duraleigh that your pool is probably on the cusp of an algae bloom with your chlorine just on the edge fighting algae and creating lots of organics (dead algae) that is getting caught in the filter. You should strongly consider getting a good test kit such as the one at tftestkits.com here or the Taylor K-2006 (not the K-2005) which can be purchased online from several sources (the TF-100 at tftestkits.com has a more logical amount of reagents and also tests CYA down to 20 ppm instead of 30 ppm in the K-2006).

    Unfortunately, if you pool's CYA is really high, you need to do a partial drain/refill to lower it. In the meantime, you can help prevent the algae growth by using PolyQuat 60 algaecide, but I'd first shock with chlorinating liquid after you get water test results (though I suspect you won't be able to shock high enough to quickly kill the algae because the CYA will be way too high -- the partial drain/refill is the most likely recommendation, but let's see the results first).

    You cannot use only Trichlor pucks/tabs when you have a cartridge filter, unless you frequently dilute the water somehow. You should be using chlorinating liquid or unscented bleach instead. If you have a plaster pool, then a CYA above 150 ppm could degrade the plaster. So knowing the CYA level is important not only for proper disinfection, but to prevent problems with plaster pools as well (see this link for example).

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  9. Back To Top    #9
    Ok here are the results FAC 3.0
    TAC 3.0
    Water PH 7.0
    TA 50
    Calcium Hardness 330
    CYA 60
    TDS 500
    Phosphates 500
    Leslie's also suggested 8lbs of alkalintity up and 5lbs of soda ash. they also suggested possibly partial drainage of pool. I don't know if this is relevant but my pool is pebble tec not plaster
    20 x 45 Inground vinyl, ~34,500 gallons,
    4 returns, 2 skimmers, dual main drain
    Pentair EasyTouch 4, IC40 SWG, MiniMaxNT 400, TR100 sand filter,
    Whisperflo .34/2 hp 2 speed, Polaris 280 w/ polaris booster pump,
    Wild ride slide, InterFab techni spring base w/ 8' InterFab olympian board
    APC 365 dark gray auto cover

  10. Back To Top    #10

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    To get to a pH of 7.5 with a TA of 100 (from your starting numbers and 15,000 gallons), you would need 7.5 pounds of Baking Soda (Alkalinity Up) and 1.9 pounds of Soda Ash (pH Up) so they were close on the Baking Soda, but not on the Soda Ash. If you added 8 pounds of Baking Soda and 5 pounds of Soda Ash as they suggest, then you would end up with a pH of 8.4 and a TA of 126 so you'd overshoot. It is true that your pool is currently corrosive to plaster/grout and that would include the binders that hold Pebble-Tek together so it's good that they suggested getting the pH back up.

    I'm very surprised at the CYA reading of 60 given your quoted usage of three 3" pucks per week. I assumed those were Trichlor pucks -- were they? Perhaps they are Cal-Hypo instead, though usually such pucks are only for special inline feeders as they tend to fall apart. Even if this CYA reading were true, you would need to maintain an absolute minimum FC level of 4.4 to avoid algae so perhaps that is why you are at the cusp at 3 ppm. Shocking to 24 ppm FC using chlorinating liquid or unscented bleach would be appropriate and I would suggest adding half the required amounts of Baking Soda (half of 7.5 pounds so around 3.7 pounds) and Soda Ash (half of 1.9 pounds so around 1 pound) since the somewhat lower pH will help the shock be more effective and you can add the rest after you are done shocking and the chlorine level has come back down. You'll need to get yourself the TF-100 or K-2006 test kit so you can accurately measure the water parameters yourself (the FAS-DPD chlorine test that comes in either kit can measure up to 50 ppm FC and has a resolution of 0.2 ppm or 0.5 ppm depending on sample size). I'd be very interested to see what you measure using your own CYA test.

    As for partial drainage (and refill) of the pool, that really depends on your true CYA level so they may be right about doing that as well. You could just do what I described above (partial pH/TA adjustment and then shock with chlorine) and get your own test kit at which point you can test the CYA level and decide what to do at that point.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  11. Back To Top    #11
    Richard thanks for the reply. The pucks I use are trichlor. I'll see about buying a better test kit. I'll follow the rest of your advise and keep you informed. Thanks again
    20 x 45 Inground vinyl, ~34,500 gallons,
    4 returns, 2 skimmers, dual main drain
    Pentair EasyTouch 4, IC40 SWG, MiniMaxNT 400, TR100 sand filter,
    Whisperflo .34/2 hp 2 speed, Polaris 280 w/ polaris booster pump,
    Wild ride slide, InterFab techni spring base w/ 8' InterFab olympian board
    APC 365 dark gray auto cover

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