What do I do about high FC?

[ksmith13]

I need some advice.
PH 7.5
FC 15.5
CC .5
TA 270
CYA 100
Salt 3700
I had been running my SWG on 20% until yesterday, I turned it off around 5:00pm, these numbers are from about 5:00 today. What should I do to lower FC? Or will it go down on it's own? If so how long will it take?

 

[Casey]

Hi and welcome to TFP!

Your FC will drop on it's own. I wouldn't worry about it but moreso, I would suggest working on getting your TA down. It is very high and you can find info on it here at pool school.

pool-school/lowering%20total%20alkalinity

 

[JasonLion]

The FC level will come down on it's own, though it will probably take a number of days to do so because your CYA level is so high. On the other hand, that isn't really all that high an FC level, given your very high CYA level. See the Chlorine/CYA Chart for appropriate FC levels for various CYA levels.

One of the problems with a CYA of 100, is that is might actually be much higher. The most common CYA test will show levels higher than 100 as if they were 100. For that reason, and several others, I strongly recommend you lower your CYA level below 100.

 

[ksmith13]

So am I correct in that the only way to lower CYA is to lower pool and replace water? How is the best way to calculate how many inches to lower? To get where I need to be? ALso since my salt is a little high I can fix that at the same time.

 

[duraleigh]

Probably the simplest way is to decide how many inches deep your pool averages.

Say your pool averages about 60 inches deep. If you drained 12" and refilled, you would lower your CYA (and salt) by about 20%.

It's not something you have to be really precise about and you may decide it's easier to do it in two or three partial drains rather than one big one. Simply retest after your first drain and refill and see how close you got to your target.

 

[ksmith13]

Thanks for all the advice, on more question. If I decide to lower water level and then refill, will this also lower TA? If so it would seem that I could do all three of the things that need to be done with only two steps (lower and refill).

 

[gtm]

Whether the TA will lower with the drain and refill depends on the TA value of your fill water. If it's less than your current pool value, it will come down. It's probably best to just refill as much as you need to lower the CYA without worrying about the TA, and then test the TA again and see where you are. It might help, but first things first, meaning the CYA level.