# Thread: How long and how hard...?

1. ## How long and how hard...?

Hi again folks!

I just spent a couple grand having my spa dug out to have leaky jets replaced. Now, everything seems to be working again.

But my pool pro lowered my Jandy AquaPure 700 down to 60%. Said I was running it too high (75%). I do trust him, but I'm curious to know if there is a grand formula to use to calculate how long and at what strength to run the thing to properly keep the chlorination (assuming FC and CYA are properly set).

2. ## Re: How long and how hard...?

There is no grand formula. You run your pumps and SWG so that your FC/CYA ratio is 7.5%. Or, simply follow the FC/CYA chart in pool school.

As the seasons change and weather cools, you'll need less pump/SWG runtime to maintain the necessary level of FC. My water temp has dropped into the high 60's and I'm only running my pump 4hrs/day with my SWG set to 25% and I still have too much FC (slightly over 10ppm). So I will be dialing down my pump run time to most likely 2hrs/day.

3. ## Re: How long and how hard...?

Thanks! My pool water never gets below 85-ish, even in "winter" here in FL.

I guess I wish there was a formula or even just a stat to show me how much Chlorine my SWG actually makes at each percentage

4. ## Re: How long and how hard...?

Every SWG produces a known quantity of chlorine gas per 24hr period. For my IC-40 its 1.6lbs/day. I think the Jandy AquaPure 700's produce 0.75lbs/day (check online or the owners manual)

Also, the SWG's all operate in duty cycle mode - 100% means fully on all the time, 50% means half on half off for a specific time period, etc, etc. Some models use an hourly time period (so 50% = 30mins ON / 30mins OFF), others use a different time period.

But, if you know the output % and the run time of your pumps, you can easily calculate how many ounces of chlorine gas is produced and PoolMath can convert those ounces into ppm FC.

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