Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 5 of 5

Thread: Late summer algae - happens every year

  1. Back To Top    #1

    Late summer algae - happens every year

    Can anyone guess what might be happening here? Every summer about early August I start to see cloudiness develop. My pool is 24000 gallons. I pump 60 gallons per minute for 12 hours a day. I keep my chlorine (SWG) at 5ppm or higher. My CYA is 50 ppm, pH is 7.5, CH is 110 ppm, Alk is 70 ppm.

    Three things change with my pool around the beginning of August: The pool is mostly in the shade almost all day long, (just two hours of late afternoon sun). I put the cover on the pool at night to keep the temperature up (78 is the best I can do with the solar heater going). And the pool is used much less, (maybe an hour or two on the weekends).

    I have to vacuum the sides of the pool at least twice a week because the south side, (the shady side), develops a green film, (presumably algae). The neighbor's very large tree to the south of the pool provides the shade as well as periodic droppings, (very nice).

    I thought that keeping the chlorine at 5ppm or higher would keep the cloudiness from happening, but I was wrong. Is there some type of algae that thrives in the shade that I should specifically be treating? The sunny side has no green film.

  2. Back To Top    #2
    linen's Avatar
    Join Date
    Jul 2010
    Twin Cities, MN

    Re: Late summer algae - happens every year

    Since the algae is mainly in the shade including on the sides of the pool, it may be Mustard Algae. See:

    Basically you do the normal shocking process until you pass the three criteria, then you bring the pool up to Mustard Algae shock level for 24 hours.
    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.

  3. Back To Top    #3

    Re: Late summer algae - happens every year

    chemgeeks's CYA chart indicates a target FC of 5.7 with a CYA of 50, you may be "riding a bit low" at 5.0...

    After you do what linen suggested, with a CYA of I'd let the FC drop down and keep it at 7.5 or 8 couple of days and watch those trouble spots. Easier to back off on the FC than play catch-up.
    In-ground Plaster 40' X 80' 144K gallon pool w/ 2 pumps (old Challenger bronze and newer Challenger II plastic) and 2 large sand filters (Pentair Triton 140's). Built in '85, in bee-yootiful shady Buffalo Gap, West Texas.

  4. Back To Top    #4

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Late summer algae - happens every year

    Quote Originally Posted by jamyers
    chemgeeks's CYA chart indicates a target FC of 5.7 with a CYA of 50, you may be "riding a bit low" at 5.0...
    He said this was an SWG so the 5 ppm FC with 50 ppm CYA should normally be OK. It could be yellow/mustard algae if it's dust-like, but it would only look green if the pool had a blue color, such as blue vinyl. Also, the general cloudiness of the pool doesn't sound right if one is circulating for 12 hours/day. Is the 5 ppm FC measured or just your estimate of where you intended to keep the FC level but that it could have dropped with higher chlorine demand? You should measure the FC just before your SWG comes back on since the FC should then be at its lowest (given that there isn't much sun on the pool).
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  5. Back To Top    #5

    Join Date
    Jun 2011
    Long Beach, CA

    Re: Late summer algae - happens every year

    You might have had a nascent algae problem that the SWG was keeping in check but has now bloomed somewhat. What size of cell do you have and what % did you have it set to?

    You should follow linen's advice.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
    Hayward Aqua Rite T-15 SWCG, Jandy LXi 400k BTU NG heater, 350 sq.ft. of Sun Star solar panels, TF-100 Test Kit, Dolphin s300i Cleaner
    Test Kits . Pool Math . Chlorine/CYA Chart . The SLAM Process

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts