High CYA and Draining

[ksweeney2929]

Have been a pool owner for a couple of years and just discovered the TFP method. I used to go to the pool store and get the water tested and add the chemicals they gave me. Starting last year, I noticed that I would be constantly brushing up what I thought was dirt on the floor of the pool. Honestly, you couldn’t really see it and the water was clear, but it when I brushed it, it looked like a cloud of dust. My levels always seemed good according to the testing but the dust would always show back up regardless of how much I vacuumed and brushed. Figured I needed to SLAM.

Same thing started to happen this year and I was worried it was mustard algae. I came across this site and decided I wanted to take over the testing. I tested my CYA and it is around 90. This is in line with my last in store test a week ago that indicated 92. I decided to drain the pool somewhat to to try to get the CYA down before I SLAM and drained about 4.5 inches last nigh and refilled. CYA didn’t seem to budge...maybe got me to 85 maybe still at 90.

We‘re draining again tonight but I’m wondering how many inches seems reasonable and should I have seen a bigger dent in the CYA?
current levels
FC - 10
CC - 0
CYA - ~ 90

Thank you!

 

[Rancho Cost-a-Lotta]

CYA will decrease at the same percentage of volume replaced. A 50% water exchange will drop CYA by 50%.

 

[Rancho Cost-a-Lotta]

If you know the surface area of your pool in sq./ft., you can multiply that number by 7.48 to calculate the volume in each foot of water. My pool has a surface of area of about 530 sq./ft. Each foot that I drain removes about 4,000 gallons in volume, or about 22% of the pool's volume.

 

[reggiehammond]

CYA testing over 90+ is tricky and inaccurate; dilute your water by 1/2 with tap water, then multiply the results by 2. Might give you a better sense of where you are today - you likely were well over 100 before the initial drain.

 

[ksweeney2929]

Got CYA down to 80 after last night's drain of another 5 inches and refill. I will do another tonight and hopefully can get it to an acceptable number.

 

[Rancho Cost-a-Lotta]

It's much more efficient to do one drain and refill if at all possible. You'll probably need to drain 1.5 to 2 feet to get to an acceptable level for a non-SWG pool.

 

[ksweeney2929]

Got it to 60 after the last drain and we were happy with that. We get full sun most of the day and felt we could work with that.

Typical New England weather…we got 5 inches of rain over three days and we had to drain some out yesterday after all that.

Appreciate all of the helpful info from this forum!