Target FC and CYA vs. SWCG recommendations

[tndtanaka]

Test results:
FC 11 working on level high
CC 0
PH 7.6
CH 750 pool stored!
TA 80
CYA 90 pool stored! Have diluted to verify.

Water temp 85 degrees
Clear water

I have read pool school and believe my target FC at my CYA level should be 8. I read in my manufacturers manual that my cya should be 30-50 and my FC 2.0-4.0 and CH 200-400. I could not achieve that without a drain and refill which I don't plan to do with pool water less than 1 year old in a drought in California in the summer at 100 heat.

My first question. Will the high target FC "cause excessive corrosion of metal components and possibly cause damage to associated pool equipment" or will my high cya protect it?

Also, where should I attempt to maintain my PH considering my high CH? I have trouble staying at 7.5 or below. My pool likes 7.6-7.8 although I admit I add acid only once a week and could do more if needed or add more acid at a time. I think I only add enough acid to bring it down to 7.4 or so.

 

[Richard320]

If you try the search function for FC/CYA relationship or somesuch, you'll find probably hundreds of threads on this very subject.

The CYA acts as a buffer, so the amount of actual hypochlorous acid in the water is lower than it would seem. Here's a link to one of chemgeek's charts. https://www.troublefreepool.com/~richardfalk/pool/HOCl.htm

Just use poolmath to calculate your minimum FC level for your CYA. Down near the bottom, select TFP and SWG and plaster in the section labelled "Suggested Goal Levels".

 

[Xexys]

With a TA of 80 such as yours, your PH may "want" to stay at 7.8 which is totally fine. Is it your pool manual or your salt cell manual that tells you to keep your CYA value at 30-50? Keeping your salt level 200-400 ppm under your cell's maximum will help stay the life of your cell and keep it from working hard to keep up with FC demand. I don't really think your high FC levels will hurt so much. If it really bothers you that much, just turn off your cell for a day or so to get your FC back in line.