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Thread: Help Determine Filter Size

  1. Back To Top    #1

    Join Date
    Feb 2013
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    Help Determine Filter Size

    New owner of an old pool here...

    I need some help determining what size filter to get. My current filter isn't doing a good job and I'd like to replace it with a new filter. I'm noticing a lot of dirt/silt on the bottom of my pool that isn't getting filtered.

    Can somebody recommend what size sand/cartridge/DE filter I should get? Details are in my signature.

    Also for reference here are my first test results with my new TF-100 kit:
    FC - 3
    CC - 0
    pH - 7.7
    TA - 130
    CH - 350
    CYA - <20

    Thanks!
    18k(ish) gallon IG plaster/painted "Lazy L" shaped pool most likely built in 1975.
    30" 500lb Hayward sand filter.
    1hp Hayward super2 pump.
    Polaris 9300 Sport Robotic Cleaner.
    TF-100 test kit with speedstir.

  2. Back To Top    #2
    Mod Squad JohnT's Avatar
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    Re: Help Determine Filter Size

    Before you condemn your current filter, 90% of the time when someone complains of silt on the bottom it's from either chlorine getting too low occasionally or it is a flow issue with the pool allowing pollen or dust to settle to the bottom before the filter can catch it.

    Fill us in on how big your pump is, how your pool is configured with skimmers, drains and returns, how you chlorinate and how long you run the pump daily.

    Not saying you don't need a filter, but no point spending money and still having the same problem.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  3. Back To Top    #3

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    Re: Help Determine Filter Size

    Appreciate the response.

    There is 1 skimmer intake in the middle of the pool and a drain in the deep end which feeds into the skimmer. There are 2 returns, one in the shallow end, and one in the deep end.

    Filter design:
    Pool has a Baker Hydropak Skimmer that has a 50sqFt cartridge filter below the skimmer basket.
    http://www.poolzoom.com/baker-hydro-...mer-parts.html
    I really don't think this is adequate for my pool. I'd like to install a modern filter with pressure gauge, etc. next to the pump.

    Pump is a brand new 1hp Hayward super 2. I'm running it 6 hours a day right now.

    Pictures of pool:
    https://plus.google.com/photos/10975252 ... NnM2OmRrAE

    I'm currently using chlorine pucks in floaters. When my CYA gets up to a proper level I'm switching to liquid chlorine only. I've been testing chlorine daily and I'm pretty sure I'm holding steady at 3ppm.
    18k(ish) gallon IG plaster/painted "Lazy L" shaped pool most likely built in 1975.
    30" 500lb Hayward sand filter.
    1hp Hayward super2 pump.
    Polaris 9300 Sport Robotic Cleaner.
    TF-100 test kit with speedstir.

  4. Back To Top    #4
    Mod Squad JohnT's Avatar
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    Re: Help Determine Filter Size

    I don't think it is possible to maintain sufficient chlorine with 6 hours of pump time, chlorination by floater and CYA that low.

    All three factors work against you in maintaining adequate chlorine.

    Floaters are notoriously slow to deliver chlorine.

    Short run time means lower circulation that can allow portions of the pool to run out of chlorine.

    Low CYA makes the slow floater chlorination even worse during sunny parts of the day.

    If your chlorine drops near zero for even a portion of the day in part of the pool, algae can get started and it just kind of hangs around without blooming causing constant dirt on the bottom until the pool gets shocked and it goes away or something happens to further strain the chlorine and it blooms.

    For a cartridge replacement, go with the largest you think is reasonable by budget and space. Though larger cartridges are expensive, you'll go longer before needing to clean it.

    For sand or DE, bigger is better up to a point. That point is where your pump can't flow enough water to fully backwash the filter. Moderate oversizing is far better than undersizing. A 24" sand filter is marginal with a 1HP pump, so I'd go bigger than that. Maybe up to 30" or so.

    I don't have any experience running a DE with a smaller pump, so somebody else will need to answer you on that option.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Help Determine Filter Size

    So any tips on recommended run time?

    Should I scrap the floaters now, add CYA in a sock, and go with liquid chlorine?

    Any reason to shock right now? When I ran full tests on Tuesday I had 0 CC..

    I was adding liquid chlorine a few weeks ago to get my chlorine levels up and holding. Since then, I've been registering about 3ppm chlorine each evening on my test strips. I'm new to all of this and just got my TF-100 on Tuesday; appreciate your advise and patience with me!
    18k(ish) gallon IG plaster/painted "Lazy L" shaped pool most likely built in 1975.
    30" 500lb Hayward sand filter.
    1hp Hayward super2 pump.
    Polaris 9300 Sport Robotic Cleaner.
    TF-100 test kit with speedstir.

  6. Back To Top    #6
    Mod Squad JohnT's Avatar
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    Re: Help Determine Filter Size

    Since you are having problems, I'd start with 12 hours of run time and then dial it back toward 8 if things clear. We generally recommend going to a 24/7schedule if the water isn't right.

    It's really your choice on floaters vs. adding the CYA. I'd add some liquid to maintain a higher level through the day.

    CC seldom shows up with algae in my experience. The OCLT is a better indication of the presence of algae than any other test. I would probably just start holding the chlorine around 8 or 10 and see if the water clears up, though shocking for a couple of days with 24 hour run time will get you there faster.

    What you are describing sounds exactly like what my pool does if I get lazy with testing. It looks like tan colored dust is falling in, but it is algae that is being mostly killed. But pool care is a very individualized "art". Your pool may need 12 hours of run time to stay clear, while somebody else two streets over might have the same pool and keep it sparkling on 6 hours. You need to experiment a little to see what works for you, and that might change during the year.

    If you can run your skimmer with no cartridge, a good setup might be to add a sand filter to the system and use that whenever the water is dirty, then stick the cartridge in when you want to clear it fast or make it as clear as possible. Many people use a skimmer sock, which is a nylon net that covers the skimmer to catch debris before it gets to the filter, and yours could be a high-end version of that.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  7. Back To Top    #7

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    Re: Help Determine Filter Size

    OK, I'll give this approach a shot and post back in a few days on how things are going.

    I like the idea of removing the cartridge and just running a sand filter with the option of dropping in the cartridge in conjunction with the sand filter when needed.

    Thanks!
    18k(ish) gallon IG plaster/painted "Lazy L" shaped pool most likely built in 1975.
    30" 500lb Hayward sand filter.
    1hp Hayward super2 pump.
    Polaris 9300 Sport Robotic Cleaner.
    TF-100 test kit with speedstir.

  8. Back To Top    #8

    Join Date
    Feb 2013
    Location
    San Antonio, TX
    Posts
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    Re: Help Determine Filter Size

    I passed the OCLT this morning, so I think I've just got some dust in the pool that isn't getting caught by my filter. The water is nice and clear, especially when the dust is settled to the bottom of the pool. I'm starting to think the cloudiness is being caused by poor filtration and chalking pool paint.

    I'm going to look into new filters very soon; I'm just not convinced mine is doing it's job. I really think I need to get a new filter that is sealed up and pressure tight. This current one is just kind of floating/sitting underneath the skimmer basket. I can't believe this was ever an acceptable design.

    I'm saving up for a re-plaster too; pool paint is a horrible idea. I'm bummed the previous owner painted it. I'd rather have ugly plaster than chipping and chalking paint.

    Anyways, thanks for the help and I'm really enjoying testing my water and knowing exactly where it is at. I've even got a daily log book going so I can watch for trends.

    Cheers!
    18k(ish) gallon IG plaster/painted "Lazy L" shaped pool most likely built in 1975.
    30" 500lb Hayward sand filter.
    1hp Hayward super2 pump.
    Polaris 9300 Sport Robotic Cleaner.
    TF-100 test kit with speedstir.

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