I’m assuming that with a week full of heavy rain and about three pool drains to get water level correct it would not be uncommon to see algae forming even with chlorine levels constantly at a 8ppm, salt, cya 60 and above?
Perfectly balanced pool with algae bloom
- Thread starter Andrew Howard
- Start date
- May 3, 2014
- 58,785
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
There is no reason you should get an algae bloom from rain. The pool water, or at least the portion on the surface, had the FC drop well below minimum. Do you keep your pool pump running during the rain? Did you test your FC daily and maintain it in the target range for CYA?
The pump runs from 8 am to 6 pm. The fc is maintained between 6 and 9 ppm. The cya did drop to 50 with all the draining. We had about 5 inches of rain in the past three days. If anything the fc was too high for the cya levels.
- May 3, 2014
- 58,785
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
So from 6pm to 8am, rain water diluted the surface of the pool water and thus FC level dropped. Only way algae can take hold is if the FC level drops below the minimum level needed for your CYA.
will definitely run the pump overnight next time heavy rain is forecasted
So, this statement can be looked at a few ways. Assuming you have an average depth of 60 inches of properly treated water, 5 inches of 0 FC rain can only mix and lower your FC by 8.3%. So if your FC was an 8, it’s now a 7.3 and still great if you were mixing.
Or 5 inches of untreated, cold rain water will sit there festering on top for up to 14 hours when the pump kicks on its next cycle, mixing the gross water into your good water. The pool water will eventually warm the rain water enough to mix them on their own, but how long that takes requires way more math than I am feeling up to at the moment. Lol.
The big take away here is that if you kick the pump on for 20 mins every 2 or 3 hours during extended storms, you’ll only lose 1FC or so in the end and still be well above minimum. If a flash flood happens out of the blue, get it mixed ASAP instead of letting it wait until tomorrow.
I’ve never thought of this before until you both made the explanation. Makes perfect sense. Guess I figured the fc would kill everything once circulated. Will definitely circulate during rain over night.
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