AutoPilot Low Chlorine

smsprague

Active member
Jun 27, 2007
37
Tucson, AZ
I have had my AutoPilot Digital with the SC-48 cell for about 2 months now and am contently struggling to keep my FC above 2. Which (I think) causes the Algae to continually grow on my pool walls. My water is clear but I have Algae (black) on the pool walls. If I run the unit in Boost mode the FC rises. I run the pump 12 hours a day with the AutoPilot on power level 3 at 90%. Here are my water stats:

SC-48 Cell
Cell Power: 28V 8.5A
20,000 Gallons
Water temp 88
Salt 3200 ppm
FC 2
PH 7.4
TA 150
CH 325
CYA 90

I need some help! Should I have gotton the SC-60 cell and is it possible to switch from the SC-48 to the SC-60.

Mark
 

JasonLion

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May 7, 2007
37,879
Silver Spring, MD
Your cell size is fine. It is just that once you have algae it is very difficult for a SWG to beat it on it's own. You need to add chlorine from another source, I suggest bleach, all at once to get the FC level up quickly to shock levels for your pool and hold it there until you don't lose any FC overnight with the SWG off. Since your CYA is 90 you should shock up to a FC of 23.

The SWG can suppliment the chlorine from bleach, but you will still need to check it a couple of times a day right at first to make sure you hold FC at 23 or above. While you are at shock level you should brush the entire pool at least once a day, plus any visible algea should be brushed several times a day until it goes away.

Once you have beaten the algae you can hopefully run at a minimum FC level of 5. Except, if that is really black algae, you may need to maintain much higher levels of FC to keep it from coming back, perhaps as high as 12. Maintaining even 12 won't be difficult with your cell once you have killed all the algae.
 

smsprague

Active member
Jun 27, 2007
37
Tucson, AZ
Jason,

Thanks for the input. How much Bleach should I add to get my FC comfortably above 25. The supermarket by me has the 96 oz jugs of 6% bleach on sale for a $1. How many of these 96 oz jugs would you suggest with a CYA of 90.
 

JasonLion

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May 7, 2007
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Silver Spring, MD
I calculate that you need ten 96 oz jugs of 6% bleach to get FC from 2 to above 25 in a 20,000 gallon pool.

You might want to try out my Pool Calculator, see the link in my signature. It is designed to do calculations exactly like this one.
 

smsprague

Active member
Jun 27, 2007
37
Tucson, AZ
I put 20 96 oz jugs of 6% bleach in the pool Sunday night. All Algae is now gone. Here are my water stats:

FC > 10
PH 7.5
TA 150
CH 325
CYA 90

Any opinions on how to keep the algae away?
 

sammm

LifeTime Supporter
May 10, 2007
257
North Richland Hills, TX
smsprague said:
CYA 90

Any opinions on how to keep the algae away?
With your CYA at 90, you will need to keep your FC level between 5-10 PPM.

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm
 

duraleigh

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Apr 1, 2007
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Sebring, Florida
Any opinions on how to keep the algae away?
Maintain your FC 5ppm or a liitle higher as posted above. Secondly, never count on the SWG to fight algae. At the very first indication of water quality problems, Use bleach to get a load of chlorine in there (at least 20-25ppm) and eliminate the organics.
 

JasonLion

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May 7, 2007
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Silver Spring, MD
Yes, turn it down. I would check it every two to three days and adjust a little in the appropriate direction each time until you get the FC to where you want it to be.