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Thread: Sand Filter Issue

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    Sand Filter Issue

    My two month old sand filter keeps blowing fine dirt back into my pool. I've tried back washing and rinsing...I've tried adding cellulose...I've tried flushing the sand till the water runs clear and always it's the same thing. Within ten minutes of turning the pump on fine dirt starts collecting at the seams and wrinkles on the bottom of the pool...the longer I let the pump run the more fine dirt appears. I though maybe bad sand so I ran the pump on recirculate and the same thing happened. The pool water itself stays clean and clear and it does not turn cloudy at all. If I stop the filter action and vacuum this fine dirt to waste and then shut off the pump the bottom of my pool stays clean. I got desperate this weekend and took the filter completely apart...triple cleaned the sand...check the stand-pipe and all laterals...took the multi-port apart and checked the spider gasket. No damage to the stand-pipe or laterals and the spider gasket looked like brand new...no knicks, grooves or twisting. When I say triple cleaned the sand I mean that I first took the multi-port top off and flushed out the sand until the water ran clear...then I dumped all the sand into a screen lined milk crate and flushed it again...then after reassembling the filter I ran it on backwash for 5-mins and then rinse for 5-mins. It didn't help at all...10-mins after turning the filter back on the fine dirt was back. I'm about ready to tear the pool down...we're in a drought out here and it's wasteful to have to vacuum to waste everyday. I've taken to doing three day cycles...I'll get the chlorine level up to a five and run the pump for 12-hrs then I'll vacuum all of the fine dirt to waste which brings the level down two to three inches which I replace with fresh water then I shut the pump down and we swim for a couple of days without filtration or water circulation. I keep the chlorine between 3 and 5 during our swim cycle...adding when needed and then getting in the pool and mixing it with arm and leg movement. I'm desperate...I like my pool...does anybody have any idea what could be causing this?
    Intex Ultra-Frame 18" x 52" with 2100-GPH sand filter

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    Mod Squad YippeeSkippy's Avatar
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    Re: Sand Filter Issue

    Do you know for sure that pool sand was used to fill it? Do you recall the brand?
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    Re: Sand Filter Issue

    Welcome to the forum.

    I believe what you have in your pool is dead algae and your issue has very little to do with filtration but water chemistry.
    I'll get the chlorine level up to a five and run the pump for 12-hrs then I'll vacuum all of the fine dirt to waste which brings the level down two to three inches which I replace with fresh water then I shut the pump down and we swim for a couple of days without filtration or water circulation. I keep the chlorine between 3 and 5 during our swim cycle...adding when needed and then getting in the pool and mixing it with arm and leg movement.
    Wow! That's a recipe for disaster and I am almost sure we can help you fix it.

    Job#1 go to your pool and pinch some of this "fine dirt" between your thumb and forefinger. Report back.....my bet is you will find you can't. It will feel slippery if you can feel it at all but more than likely it will just "poof" away when you try to capture it.......that's not dirt.....that's dead algae. Let us know what you find.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Sand Filter Issue

    Yippieskippee...I don't remember the brand of the sand but it was bought from Leslies Pool Supply ad it said it was specifically for pool filters on the bag.

    Duraleigh...I thought about the dead algae thing too but a couple of things trouble me about that. I did have an algae problem in the spring but I used green away and super-slammed the pool. It took a couple of weeks for the water to fully clear up. I vigilantly brushed the pool during this time and vacuumed all dead algae to waste when it settled. That was three months ago...since then I've had the water so clear that you can see the date on penny at the bottom...that might be a little exaggeration but I'm pretty sure that I got rid of any dead algae suspended in the water and I'm even more sure that the algae was killed off. The first thing that troubles me about the algae scenario is that this stuff only shows up when the pool pump is running...If I clean the pool and shut the pump down nothing appears at the bottom and the water is crystal clear. Wouldn't dead algae settle to the bottom with or without the pool pump running? This stuff doesn't look like dead algae either...it's brown like dirt...not white or gray. It does go "poof" when you rub your foot across it though. The other thing is there is no slippery or slimy feel to the bottom or sides of the pool. Last time I checked my pool chemistry everything was good except that the CYA level was low for a vinyl pool. I'll try and re-test tonight and post results tomorrow.

    I do appreciate the help on this...
    Intex Ultra-Frame 18" x 52" with 2100-GPH sand filter

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    GreatCanadian's Avatar
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    Re: Sand Filter Issue

    Yes you may indeed have cleared up your algae the spring. But you say you bring your chlorine level to 5, and not add any more for a couple of days?? Depending on your CYA level, you could be inviting trouble. My guess is algae. And trust Duraleigh. He knows what he's talking about.
    13'x22'x52" 8,000 gallon ProSeries Pool with Borates
    Intex 110 pound Sand Filter with Zeobrite, 2650 gph pump, 0.95 hp
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    Re: Sand Filter Issue

    Pump running, the flow of the water will tend to "clump up" dead algae into the seams and tiny low spots. Pump off, the algae settles pretty evenly across the pool floor so you don't see it.

    Can you post a set of current test results?

    pH
    FC
    CC
    TA
    CH
    CYA
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Sand Filter Issue

    Quote Originally Posted by densbusiness View Post
    Yippieskippee...I don't remember the brand of the sand but it was bought from Leslies Pool Supply ad it said it was specifically for pool filters on the bag.

    Duraleigh...I thought about the dead algae thing too but a couple of things trouble me about that. I did have an algae problem in the spring but I used green away and super-slammed the pool. It took a couple of weeks for the water to fully clear up. I vigilantly brushed the pool during this time and vacuumed all dead algae to waste when it settled. That was three months ago...since then I've had the water so clear that you can see the date on penny at the bottom...that might be a little exaggeration but I'm pretty sure that I got rid of any dead algae suspended in the water and I'm even more sure that the algae was killed off. The first thing that troubles me about the algae scenario is that this stuff only shows up when the pool pump is running...If I clean the pool and shut the pump down nothing appears at the bottom and the water is crystal clear. Wouldn't dead algae settle to the bottom with or without the pool pump running? This stuff doesn't look like dead algae either...it's brown like dirt...not white or gray. It does go "poof" when you rub your foot across it though. The other thing is there is no slippery or slimy feel to the bottom or sides of the pool. Last time I checked my pool chemistry everything was good except that the CYA level was low for a vinyl pool. I'll try and re-test tonight and post results tomorrow.

    I do appreciate the help on this...
    What do you mean by "super-slammed"? Did the pool pass an OCLT? Were the CC's <0.5ppm?

    Can the pool pass an OCLT now?

    Keeping the chlorine between 3-5 means nothing without a CYA level. Is the "3-5" TC or FC?

    What kind of test kit are you using?

    Please post the test results that Dave mentioned so we can better help you.

    I believe you are (luckily) catching the beginnings of an algae bloom and need to react quickly before it gets out of hand. An OCLT and full set of results is needed.

    Dom
    Dom - TFP Guide
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    Re: Sand Filter Issue

    Quote Originally Posted by densbusiness View Post
    My two month old sand filter keeps blowing fine dirt back into my pool. I've tried back washing and rinsing...I've tried adding cellulose...I've tried flushing the sand till the water runs clear and always it's the same thing. Within ten minutes of turning the pump on fine dirt starts collecting at the seams and wrinkles on the bottom of the pool...the longer I let the pump run the more fine dirt appears. I though maybe bad sand so I ran the pump on recirculate and the same thing happened. The pool water itself stays clean and clear and it does not turn cloudy at all. If I stop the filter action and vacuum this fine dirt to waste and then shut off the pump the bottom of my pool stays clean. I got desperate this weekend and took the filter completely apart...triple cleaned the sand...check the stand-pipe and all laterals...took the multi-port apart and checked the spider gasket. No damage to the stand-pipe or laterals and the spider gasket looked like brand new...no knicks, grooves or twisting. When I say triple cleaned the sand I mean that I first took the multi-port top off and flushed out the sand until the water ran clear...then I dumped all the sand into a screen lined milk crate and flushed it again...then after reassembling the filter I ran it on backwash for 5-mins and then rinse for 5-mins. It didn't help at all...10-mins after turning the filter back on the fine dirt was back. I'm about ready to tear the pool down...we're in a drought out here and it's wasteful to have to vacuum to waste everyday. I've taken to doing three day cycles...I'll get the chlorine level up to a five and run the pump for 12-hrs then I'll vacuum all of the fine dirt to waste which brings the level down two to three inches which I replace with fresh water then I shut the pump down and we swim for a couple of days without filtration or water circulation. I keep the chlorine between 3 and 5 during our swim cycle...adding when needed and then getting in the pool and mixing it with arm and leg movement. I'm desperate...I like my pool...does anybody have any idea what could be causing this?
    Did you figure this out? I have the same exact issue. Tired of vacuum each time. Within a few minutes I see the dust by the seams. I did the overnight FC test and it passed so I know it's not algae. The pool is crystal clear, I haven't taken the sand filter apart or looked inside yet. When I had the pump I didn't have this problem. I also bought the sand from Leslies Pool Supply, which makes me think maybe that's the problem. I still have a bag left so I'll take a picture tomorrow and post here.
    --------
    Intex 22' x 52" Ultra Frame - approx 10,000 gallons of water
    Intex Sand Filter pump (8hrs Run Time)
    Krystal Clear Saltwater Model 7110/8110 (6hr run time/day)
    K-2006 TEST KIT

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