Rounding Up CYA

jamesey

Member
Apr 27, 2021
13
Maryland
Pool Size
17000
Surface
Plaster
Just completed a drain & refill and added stabilizer a few days ago to bring CYA levels up to 30 ppm. My TF100 test is currently reading between 20-30 ppm (right in the middle). After doing some searching here, I'll be rounding up to 30 and maintaining my FC levels from there. Am I making the right move here? Or should I add another 10ppm to try and bring it between 30-40pm?
 

dianedebuda

Gold Supporter
Jan 2, 2018
558
Austin TX
Pool Size
24500
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
From what I understand: if you can't see the dot at the 20 level, it's 20; if you can't see the dot at 30, it's 30. Nothing inbetween.
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
5,150
NW Ohio
Yep, round up. The margin of error on that test is fairly significant (I'm sure you guessed that) and since the FC/CYA Chart has quite a bit of upward room (you can safely swim to SLAM level with no real discomfort) it's better to be a bit on the high side than on the low side.

To answer the last question, I personally would add a bit more CYA. As summer starts to roll in you're probably going to see a fair bit of chlorine burn off with only 30 ppm CYA in your water. Bringing it up to 40 or 50 will help control that a bit better. I know it seems counter intuitive, but a higher CYA with higher chlorine level can sometimes mean using less chlorine because you lose less during the day.
 
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wireform

Silver Supporter
In The Industry
Aug 15, 2017
3,115
Spring Valley, NY
He's in Maryland. I wouldn't go crazy with CYA unless it's a SWCG pool otherwise a solid 30 works. You may want to check it again in a month incase you lost some from splash out or lots of rain requiring pump off to bring water to proper level.
 
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jamesey

Member
Apr 27, 2021
13
Maryland
Pool Size
17000
Surface
Plaster
It's only been about 3 days since the drain & refill, but I'm only losing about 1-2ppm FC daily. I test once in the morning and again in the evening and add bleach as needed to maintain the recommended 6ppm by PoolMath

@wireform - curious to know your thoughts. What is it about Maryland that would make you lean on the lower end?
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
3,115
Spring Valley, NY
For a chlorine pool 30 will get you by unless the pool is flat out in the sun all day. Out west like in Texas lots of unending sun will demand a bit more cya even for a non SWCG pool.
 

jamesey

Member
Apr 27, 2021
13
Maryland
Pool Size
17000
Surface
Plaster
Ah, yes. Our pool is partially shaded throughout the day by two large pine trees in our yard which helps.

I'll keep the CYA as-is and monitor it monthly. Thanks again everyone!
 

DeanP66

Well-known member
Mar 26, 2014
1,230
San Jose, CA
Also, if you go up to 40 or even 50, you can go every other day between dosing because the FC will burn off much more slowly. If you're at CYA 30, then you want to have your FC in the 4 - 6ppm range and never below 2ppm. You could easily burn 2-3 ppm daily, which means you'll be at your minimum daily so if you miss a day dosing, you could be in jeopardy of something starting to grow in the water. If you go with CYA 50, then you dose FC up to 8 ppm and never let it get below 4. At CYA 50, you'll lose less FC daily, maybe 1-2 ppm in your case, which could let you ride an additional day between your next dose. Just food for thought.
 
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jamesey

Member
Apr 27, 2021
13
Maryland
Pool Size
17000
Surface
Plaster
One bit of information that I left out (it just arrived yesterday) is that we'll have a solar cover on when the pool is not in use. I'll continue to monitor FC daily as the summer heat rolls in and if it gets too much to handle, then I'll boost my CYA up as recommended here.

Bit more background- The reason why we performed the drain & refill was because the old homeowners let the CYA get out of control with shock and 3" pucks. After going through that process I know it's easier to add CYA then to reduce it, so I'll error on the lower end for now.
 

DeanP66

Well-known member
Mar 26, 2014
1,230
San Jose, CA
I went through the same thing with my pool guy. He used nothing but tablets and when I decided to take over the pool duties myself, the CYA was up over 200. I was also weary of letting the CYA get too high after the drain and fill, but realized that the FC loss daily put me in jeopardy of having too little chlorine in the pool. I raised CYA to 50 and NEVER put anything in the pool with CYA in it so it never goes up.
 
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