Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 8 of 8

Thread: Algae and cool water

  1. Back To Top    #1
    meatloaf's Avatar
    Join Date
    Feb 2008
    Location
    Gilbert AZ
    Posts
    373

    Algae and cool water

    My pool water is 71*. I am adding 14oz of 10% bleach daily and maintaining FC of 2. My question is, at what temp will the possibility of algae stop and will I have to add chlorine even if the water is too cold for algae to grow?
    Thanks
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

  2. Back To Top    #2
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    Location
    SouthWest Alabama
    Posts
    22,347

    Re: Algae and cool water

    The accepted temp at when algae stops is about 60ºF. Below that it's usually not a problem.

    If you cover your pool you should raise the FC and not worry about it till next spring when the water temp is going to get above 60ºF on a regular basis.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

  3. Back To Top    #3

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Algae and cool water

    During the winter, I add chlorine about once every few weeks to a month as the chlorine usage drops to < 1 ppm FC per week at colder temps. Though you can ignore the chlorine level when the temps are cold, it's a bit safer to check on it once in a while and boost the FC as needed if that's not hard to do -- at least when a pool isn't completely closed (i.e. it isn't drained down at all and the circulation pump is still used every day though for less than a turnover).
    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"

  4. Back To Top    #4
    meatloaf's Avatar
    Join Date
    Feb 2008
    Location
    Gilbert AZ
    Posts
    373

    Re: Algae and cool water

    Thanks for the info. I thought that it was 60* or below but I wasn't sure.
    My pool is a 10,500 gallon (420 Sq Ft ) kidney shape. A hand made sheer decent waterfeature. STA-RITE HRPB30, Sand filter 30" 98 GPM,
    1 HP Maxi-Glas 2 pump, BBB Method, Taylor K-2005 test kit, 50 Watt 12V low-voltage pond light illuminates the pool at night for a nice soft glow.
    250 gallon stand-alone hot tub. Got it FREE!

  5. Back To Top    #5

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Algae and cool water

    Figure 1 in this paper gives a rough idea of the maximal algae growth rates as a function of temperature. The generation time, which is how long it takes to double in population, is a little over 5 hours at 86ºF but drops down to a little over 12 hours at 59ºF. Algae can still grow even near freezing temps, but the growth rate is much slower (someone on The PoolForum saw algae slowly growing under their frozen-over pool!). Note that these numbers are maximums assuming ideal nutrients and sunlight. This link in Figure 3 shows growth rates are temperature-dependent in a very species-specific way.

    In practice, when the water temp gets colder, the amount of light is also reduced as more days are cloudy and the sun is lower in the sky. This one-two punch significantly slows down algae growth rates. If one also covers the pool with an opaque cover, then that cuts down sunlight even more.

    Of course, if there is any chlorine or algaecide (including borates) leftover in the pool, then that can inhibit algae growth as well.
    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"

  6. Back To Top    #6

    Join Date
    Jul 2010
    Location
    northern California
    Posts
    235

    Re: Algae and cool water

    I live in northern California. Although the night temperatures had been in the low 40's to mid 30's during the past 2 nights, we still had a lot of sunshine during the day. The chlorine consumption in my pool is still about 1.0 ppm per day for the past 2 days. It was about 1.5 to 2 ppm per day in the summer. I keep FC at a minimum of 7 because I had mustard algae twice this year. The question is: should I maintain FC at 7 in the winter or can I go lower? The pool stays open year round and I don't want to battle mustard algae again. The water temperature this morning was 60 degrees.
    IG pebbletec pool: size of pool: 27,000 gal; filter: cartridge - Hayward Superstar Clear; pump size: 1.5 HP; TF 100 Test kit - got it on 7-29-10; The Pool Cleaner-4-wheel suction model; Pool calculator: http://www.poolcalculator.com/; bleach calc: http://troublefreepool.com/files/BleachCalc262.exe

  7. Back To Top    #7

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Algae and cool water

    Though the growth rate of algae slows down as water gets colder, the reaction of chlorine killing algae also slows down. So lowering the FC level too much could be risky. The main advantage of the cooler water, especially if the sun isn't on the pool due to clouds or a cover, is the lower daily FC usage. I'd keep the FC at whatever level you normally need to do to prevent algae. Though it's possible that at some cold water temperature the algae growth plummets, why take the chance that it doesn't?
    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"

  8. Back To Top    #8

    Join Date
    Jul 2010
    Location
    northern California
    Posts
    235

    Re: Algae and cool water

    Thanks chem geek. I needed the reassurance.
    IG pebbletec pool: size of pool: 27,000 gal; filter: cartridge - Hayward Superstar Clear; pump size: 1.5 HP; TF 100 Test kit - got it on 7-29-10; The Pool Cleaner-4-wheel suction model; Pool calculator: http://www.poolcalculator.com/; bleach calc: http://troublefreepool.com/files/BleachCalc262.exe

Posting Permissions

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