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Thread: Blue precipitate on pool bottom

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    Blue precipitate on pool bottom

    So, the ongoing fight against the waxy film on the surface goes on. Today, after having been absent from pool care duties for two days, I observed a beautiful azure powdery substance on the bottom of the pool. Although quite pretty, I vacuumed it up and then cleaned the filters. It was essentially the same stuff that I was able to skim off the surface. So, blue to me means copper. But there are no copper components in the pool. Any ideas?
    All of this started after adding a large quantity of soda ash in divided doses to treat a pH of less than 7.0 (measured to be 6.8 by Hanna pHEP meter). Sounds like the process of Saponification, like when you add lye to oil and get soap.
    This is frustrating because I have owned the pool for 15 years and done nothing but add 3" tablets and an occasional shock when green algae got a start. Never had a problem with waxy film, blue precipitate, and grey/blue stained bottom. Only thing different is that we "skipped" last season, the cover stayed on from September 2011 until May 2013.
    Sacramento CA
    33,000gal, IG, circa 1970, (now) fiberglass over plaster, pac-fab paper cartridge, 1.5hp pump, polaris 280 (inoperable, UV damage) with booster, solar heat (inoperable, leak in powermat), skimmer (inoperable, line clogged & possibly fractured under concrete), main drain inoperable (long standing problem), jury rigged deep intake, skimmer line work-around in progress.

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    UN1017's Avatar
    Join Date
    May 2012
    Sacramento, CA

    Re: Blue precipitate on pool bottom

    After looking over your signature line and previous posts, it sounds like you have your hands full. Many of the equipment issues are affecting your water but it seems that you have some water chemistry issues.
    Quote Originally Posted by conrad.arnold
    This is frustrating because I have owned the pool for 15 years and done nothing but add 3" tablets and an occasional shock when green algae got a start.
    I'm sure you've been poking through this site and have now realized that your chemical choices could have brought you here. Many tabs contain copper so it doesn't have to be from a part of the pool. It is common for metals to precipitate out when there is a significant rise in pH.

    You will need to post a full set of results to get this ball rolling. It looks like you ordered a test kit, so I would hit Pool School until it arrives. FYI....if your CYA is truly 80, then you would most likely require a partial drain anyway. With that CYA, you need to get your FC over 30 to reach proper shock level.

    15'x30' IG - Roman-style - 14K - Pebble Fina Classico
    Filter: Jandy CL460 Pump: Jandy Stealth SHPF1.5 SWG: Jandy AquaPure 1400 Cleaner: Jandy RayVac Test Kit: TF-100 w/SpeedStir

    Chlorine/CYA Chart----Extended Test Kit Directions----SLAM

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