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Thread: Murky water after cleaning filter

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    Murky water after cleaning filter

    Hi everyone. I'm a newbie here and to pools in general. We installed an above ground pool last summer and it's been trouble free until recently. I realize that one of the prerequisites here is to have a good testing kit. Unfortunately I've only been using those test strips. Maybe out of dumb luck my pool water has been sparkling clean until recently when I cleaned the cartridge filter about 2 weeks ago. This was the third time I cleaned the filter this season. The past two times, there were no problems. This time, I noticed that when I turned the pump back on after cleaning the filter, a bunch of grey-ish water came out of the return. I'm guessing it's the water that was in the filter housing. I figured that the filter would clean it up but ever since then, the water in the pool has been a bit murky. Before I was able to see straight to the bottom, now I have to strain my eyes to see it. I've added a bit more algaecide and super clarifier to no avail. I've even replaced the cartridge filter with a brand new one, but barely a change. The water is not green, it's just murky, grey-ish. According to the testing strip, all levels are ok, including free chlorine. In fact, per the strips, the balance has been very steady for ph, alkalinity, free chlorine, stabilizer, etc. Any suggestions?

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Murky water after cleaning filter

    Welcome to TFP.

    You're like a good number of people that come here. You have been having no problems until now. That's what we're here for.

    What do you use to chlorinate your pool with?
    What brand and model filter do you have?
    Did you inspect the headers in the filter to make sure one wasn't cracked?
    Tie a sock or stocking over a return and see if debris is bypassing the filter.

    Now the statement you expect! You really need a good test kit. Just go ahead and order the TF-100 and a speedstir. You won't regret it.

    Now for the rest of the story. If you read and learn here you'll have no need for algaecide or clarifier. Both of which can make your water cloudy.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Murky water after cleaning filter

    Sorry it has taken so long to respond. I have finally received my TF-100 testing kit for properly testing my water. In the meantime, since I didn't know exact levels, I added 25 ounces of 8.25% bleach on an almost daily basis. This was based on my estimation that CYA was in the 80 range and my FC needed to be brought up to target FC of 9. Of course, after the first day, the test strip was useless as it maxed out at 10.

    Then, by accident, one of the pipes that connects my solar heater slipped off slightly which was apparently enough to drain my pool below the return. So about 1 to 1.5 foot of water was drained out. I've disconnected the solar heater and reconnected just the pump and filter. Filled the pool back to proper levels and shocked it using cal-hypo 78%. Used cal-hypo mainly because I haven't found a place nearby that sells high % bleach. Since my pool is vinyl and cal-hypo does not add CYA, I figured it should work for now.

    Here are the results.

    FC = 35
    CC = 0.5
    PH = 7.5 (probably not accurate as FC is high)
    CYA = 110

    Unfortunately CYA is higher than expected even after the partial drain / refill. FC is near slam level for CYA 100. So here is my question: If I keep it at FC 35 or maybe raise it a bit to 40, should that clear out the mirky water, which I'm thinking is algae now?

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    Mod Squad zea3's Avatar
    Join Date
    Jul 2009
    Houston, Texas

    Re: Murky water after cleaning filter

    Use the Pool calculator to determine what your slam level should be and try to keep the pool at slam level as much as possible by testing the water every couple of hours and adjusting the chlorine as needed. Once you have met all 3 criteria (1. clear water, 2. passing the overnight chlorine loss test, and CC of .5 or less) the slam process is complete and you can let the FC drop to daily target levels.

    Keep an eye on your CH level if you continue to use cal-hypo to slam. Too much CH is problematic for all types of pools.
    TFP Moderator
    Helpful links: TF Test Kits,TFP Pool School, PoolMath
    Vogue 21' round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
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    Re: Murky water after cleaning filter

    Little confused here. Per the Chlorine / CYA chart FC for 100 CYA is 39. Per the pool calculator FC for 110 CYA is 26. That's a big difference. Am I using the pool calculator incorrectly?

  6. Back To Top    #6
    linen's Avatar
    Join Date
    Jul 2010
    Twin Cities, MN

    Re: Murky water after cleaning filter

    Yes they are different, but both will work. The chlorine/cya chart is more aggressive and should clear the pool faster.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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