Pool Math salt cell recommendation too high

dcp063 said:

PoolMath says at 50% I need to run my pump for 13.75 hours.

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To achieve how much FC generated?

With a CYA of 80, you want to run your FC higher. Always follow this link-->FC/CYA Levels

Min is 4 for CYA of 80, target is 6-8. You be flirtin' with the green stuff....

18k gal pool, 80 CYA. FC/CYA chart indicates your minimum is 4ppm, target is 6ppm. You need to get chlorine into your pool. Running below minimum, you don’t want any nascent algae blooms. Join the FC #runhot club.

Pool math indicates that running your T-15 for 13.75 hours set at 40% will yield 2.8 ppm FC. You might get away with for now. But not in a month. I personally would add a gallon of 10% which would add 5.6 ppm today and then maintain target 6 with your T-15 SWG. (Personally, I run hot. I maintain 8 ppm, 2 ppm above target.)

The amount of UV a pool gets is variable during the year. You are experiencing it.

You need to manage the run time and %output to match the FC demand...and keep your FC in range for your FC...

The recommendations that PoolMath makes in the FC Overview can be a bit confusing. It just tells you how long you have to run the SWG to increase FC from "Current Free Chlorine" to "Target Free Chlorine". PoolMath doesn't consider the chlorine you will be losing throughout the day, it doesn't even know how much that would be.

You have to add the estimated chlorine loss to the target level you want to get to.

Once you are at your target FC, you basically want to create as much chlorine pet day as your are losing per day.

Say, you want to maintain an FC level of 8ppm, and you know that you are losing 3ppm over a day. Then you put 5 into the current field and 8 into the target field, and PoolMath will tell you how long to run the SWG to create the delta of 3ppm.

Ideally you will never get down to 5, because your SWG continuously produces chlorine as it is lost. You will just fluctuate a bit around 8ppm. In the morning you produce chlorine faster than it is lost and FC might rise a bit, around noon the sun eats it faster than you produce it and FC drops a bit, and in the evening it catches up again. But you still put that value as your current value where FC would drop down to if the SWG wasn't running.

In the end, PoolMath just tells you how much to add of a chemical or how long to run the SWG to achieve a change from current to target for the respective parameter. You have to do the actual thinking (based on the knowledge you got from all the TFP sources) and put the correct values into PoolMath. The numbers that PoolMath prefills the target fields with are just that - numbers. You are in charge there to make sure that these numbers make sense for your pool.