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Thread: Algae in filter

  1. Back To Top    #1

    Algae in filter

    Hi folks,

    Sorry for the length of this....

    For a couple of weeks, I've been fighting a tendency for my pool water to go ever so slightly cloudy and green-ish. FC levels and PhD were always kept quite good (FC between 7-10 and Ph 7.4-7.8), with almost never any evidence of CC. CYA os good too, somewhere between 40 and 50. (Water temp. high however, at 85 degrees.)

    Still I am being plagued with considerable amounts of what I *think* is fine and loose dead algae drifting on the pool bottom (there may well be pollen there too), and while it does come up with a vaccuum, the next morning it will be there again. Moreover, whenever I start the pump up after vacuuming, I get a pretty substantial stream of cloudy water coming out of the return jet--it lasts for about 7-8 seconds.

    This morning I pulled the valve assembly off the top of my sand filter, and discovered quite a bit of green algae growing on the inner walls of the filter. As well, a layer of algae had spread across the top of the sand, extending about two inches from the wall. This algae seemed pretty healthy, so to speak. After excavating the algae--or miost of it--I poured a good bit of straight bleach around the top of the sand and on the inner sides of the pump.

    I've since dug out the algae by hand, and am going to pick up a bit of filter sand later this morning. I plan to remove much of the sand from the filter, have a look at the bottom of the filter assembly to see if anything's amiss, and then fill with new sand.

    I just want to ask the board if there's anything else I should be looking for, and perhaps also what might have brought on the algae growth in the filter. We did have a very mild winter, and although I drained the pool and filter, I'm sure the inside of the filter remained damp over the winter. My pump tends to run at about 10psi.

    best and thanks to all,
    11,500 gal. rectangular cement, 11 x 28 (built c1930); Hayward S180T sand filter; Hayward Max-Flo II 3/4 HP pump

  2. Back To Top    #2

    Re: Algae in filter

    Algae needs sunlight to grow, so likely if it is algae, it is what has just been filtered out of your pool water and collected in the filter.

    If your water hasn't been clear, you need to go through the shock process... see "Pool School". It is a process... as I said, and not a product. You can't go out and buy "pool shock" and follow their directions and expect to have a clear pool... It doesn't work that way.

    As far as the filter goes... a good check of it is not a bad idea if it is spitting into the pool and you've not had that trouble before. Could be that you didn't rinse after a backwash and wait 30 seconds or more before kicking the filter back on to filter mode, could be that your sand needs rinsed well, or that you have a broken lateral (finger). Generally you don't need to change sand unless you've done a conversion from bacquacil to chlorine... an occasional rinse of the sand with the hose and good chlorine levels and your sand should do it's job just fine.
    Indiana, ABG 24'x52" Galveston by Blue Cascade (Craigslist $600 w/part of deck included), 13,500 gallons, Intex SWG, solar panel

    My backyard is like a park... Why then does DH always want to go camping??? I just don't understand.

  3. Back To Top    #3

    Re: Algae in filter

    Thanks for the reply; I should realize that algae needs sunlight (duh). In what you write, the only thing I can see that might be at work--besides the need to shock and of course the unknown about the state of the laterals--is that, no, I typically have *not* waited 30 seconds after backwashing/rinsing to go back to filtering. I generally switch to "filter" right after having rinsed. Honestly, I've not know that one was supposed to wait, but it makes perfect sense. Oh well...

    I'm familiar with shocking the TFP way, and will do that.
    11,500 gal. rectangular cement, 11 x 28 (built c1930); Hayward S180T sand filter; Hayward Max-Flo II 3/4 HP pump

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