Effects of higher FC than CYA/FC chart?

[FlGator68]

Hey TFP team, I’ve been on here a few years and you guys have been immensely helpful in maintaining my pool. I have a question I couldn’t find in Pool School.

I have a SWCG in my 8500gal pool in Florida.. where water temp is over 90 most of the summer. I have been keeping my CYA at 75 and the chart recommends 5-10 for FC. Wondering what the downside/effects are of running CYA 75 and FC closer to 12-13?
I feel like I read about chlorine lock years ago but not sure what that was about and if it applies. Thank you!

 

[mknauss]

Only issue is the ability to accurately measure pH and quicker expiration of your SWCG.

 

[Donldson]

Chlorine lock is just a catch-all term used by industry members when they're stumped. It's not a real thing.

 

[cwswifty]

How are you measuring a CYA of 75? That isn’t possible with the Test Kits recommend here.
Test Kits Compared

What is motivating you to run higher than recommended FC levels?

 

[wireform]

His motivation would be mine too with a small body of water and a few more swimmers at the same time can and will bring the FC down fast so to be on the hot side and remain there isn't the biggest sin as it's still miles from slam high.Yes the CYA is called 80

 

[FlGator68]

How are you measuring a CYA of 75? That isn’t possible with the Test Kits recommend here.
Test Kits Compared

What is motivating you to run higher than recommended FC levels?

I use the Taylor K-2006C that I believe was recommended here 5 years ago when I bought it.

It’s a small pool in hot weather and the FC can fluctuate a lot in a couple days so I tend to keep it in the 12-13 FC range but not sure if there is a downside.

 

[FlGator68]

I use the Taylor K-2006C that I believe was recommended here 5 years ago when I bought it.

It’s a small pool in hot weather and the FC can fluctuate a lot in a couple days so I tend to keep it in the 12-13 FC range but not sure if there is a downside.

Follow up comment.. I had a bunch of kids swimming all day yesterday and today the pool has a slight white haziness, which looks like pre-algae. So I tested and I was at 65 CYA and 10.5 FC.. so it doesn’t seem like it should be clouding but it is. Cleaned the filter today just to be sure so I’ll see if it filters out today.

 

[cwswifty]

I use the Taylor K-2006C that I believe was recommended here 5 years ago when I bought it.

It’s a small pool in hot weather and the FC can fluctuate a lot in a couple days so I tend to keep it in the 12-13 FC range but not sure if there is a downside.

Ah ok. Always round up to the next CYA level. Example: 75 = 80. Here’s a pH meter I have that has been remarkably accurate without the need to recalibrate often. Another benefit for some is that it accurately measures pH when FC is above 10.0.

https://a.co/d/4Jxgxyd

 

[PoolStored]

I use the Taylor K-2006C that I believe was recommended here 5 years ago when I bought it.

My guess is your reagents are old, and causing more drops. Newer reagents would require less drops, so your FC is not likely 10.5.

Have you replaced them recently? Have you ever replaced them?

 

[wireform]

Follow up comment.. I had a bunch of kids swimming all day yesterday and today the pool has a slight white haziness, which looks like pre-algae. So I tested and I was at 65 CYA and 10.5 FC.. so it doesn’t seem like it should be clouding but it is. Cleaned the filter today just to be sure so I’ll see if it filters out today.

You can add 64 ounces of LC 12.5% which should add about 7ppm FC to help clear it up.

 

[FlGator68]

My guess is your reagents are old, and causing more drops. Newer reagents would require less drops, so your FC is not likely 10.5.

Have you replaced them recently? Have you ever replaced them?

That’s a good question, I test once a week, every week, then I replace them when they run out. However I buy the larger 2oz versions and it looks like the last time I bought FC reagent was almost 3 years ago.. should I assume expired?

 

[PoolStored]

Yes, past due. I'd replace them.

Best deal around... Link--> TFtestkits.net

 

[FlGator68]

Yes, past due. I'd replace them.

Best deal around... Link--> TFtestkits.net

Just ordered a new kit from the link, thanks!

I’ve been using a speedstir for years but always thought it threw off the results on the FC.. has anyone else seen that happen? I use it to stir the granules but then I manually stir the reagent in because I got very different results with the speed stir, thoughts?

 

[proavia]

Using the speed stir is more accurate and consistent.

Hold reagent bottle perfectly vertical.
Dispense 1 drop per second.
Let each drop fully form on the tip and drop from its own weight.