High CYA, first time LC user

[Texas Splash]

Also, I’ve been doing my scrub after my final LC application of the day but before my final test of the day. Not sure if that’s relevant. I vacuum with my dolphin every morning in the 2 hour walls and floors mode.

It sounds like you're doing all that's required from a cleaning perspective. Your biggest issue appears to be some sort of chemical presence (not ammonia though) that was tearing up the chlorine in the beginning. Perhaps there's something residual in that drain area that is stalling your OCLT progress. Since you have the old vacuum port closed, I would not suspect that as a problem.

 

[jeffchap]

CYA was still 60 as of yesterday. I always dose targeting 24 at least 3 times a day but it never seems to quite get there. Maybe I should add an extra 50% every time. Running out of R-0871 though, shipment won’t be here until Tuesday.

Maybe your pool is larger than you think it is?

 

[bja1288]

Maybe your pool is larger than you think it is?

Very possible. Previous owners had it 2 years, (not original) told me 32k. Everyone that looks at it was skeptical so I measured it as 22k. It is elongated oval, 37 feet long 17 feet wide, 3 foot shallow end 8 ft deep end.

 

[jeffchap]

Some of us with irregularly shaped pools have backed into figuring out the volume by adding a given amount of chlorine and comparing the actual change in FC to the expected change from Pool Math.

 

[bja1288]

@jeffchap might have nailed it. I still can’t come up with an equation that would make this a 32k pool but it sure acts like it. Started treating it as 32k yesterday and got much better results. Close but no cigar on the OCLT.
7/3/22: FC 23, CC 0.5 -> FC 21.5, CC 0!

 

[bja1288]

Thinking again, I feel like the more likely scenario is that the LC isn’t as strong as it says it is considering my CYA halved when I replaced 12k gallons. The oldest LC i’ve used had a date of 5/23/22.

https://www.menards.com/main/outdoors/pools-accessories/pro-clor-liquid-pool-shock-1-gal/pc160003/p-1444426383664-c-10137.htm?tid=4203505932949875147&ipos=25

 

[IceShadow]

I bought a gallon of LC on Friday night (6/30) from Menards that had a date on it of 6/21. I’ve never seen a brighter green LC when I poured that puppy into the pool

 

[bja1288]

Two days in a row with a 1.5 FC drop and 0 CC. I did not pull off my main drain cover because I don’t have a spotter other than my wife, who I don’t feel comfortable pulling me out. I did brush it as much as I could.

One thought - I typically only backwash when the pressure rises, and it hasn’t started rising yet. I last backwashed on 6/23. Would that help?

 

[IceShadow]

Two days in a row with a 1.5 FC drop and 0 CC. I did not pull off my main drain cover because I don’t have a spotter other than my wife, who I don’t feel comfortable pulling me out. I did brush it as much as I could.

One thought - I typically only backwash when the pressure rises, and it hasn’t started rising yet. I last backwashed on 6/23. Would that help?

If the pressure hasn’t risen there’s no real reason to backwash. Right now something is eating the chlorine and it’s hiding somewhere. Gotta keep searching for that “aha!” moment…

 

[bja1288]

10 days and 56 gallons of LC later… I am done. Never really got the aha moment, so this could have been a fluke test but I’m so tired of brushing. I’m gonna call it done. Thanks so much everyone for your help. Lot of lessons learned here.

6/27: 6.5 FC, 2 CC -> 0 FC, 0.75 CC
6/28: 18 FC, 1 CC -> 10 FC, 1 CC
6/29: 22 FC, 1 CC -> 14.5 FC, 0.75 CC
6/30: 18.5 FC, 0.75 CC + 1 gal 12.5% -> 18 FC, 0.5 CC
7/1: 21.5 FC, 0.5 CC -> 16.5 FC, 0.5 CC
7/2: 22.5 FC, 0.5 CC -> 17.5 FC, 0.5 CC
7/3: 23 FC, 0.5 CC -> 21.5 FC, 0 CC
7/4: 23.5 FC, 0.5 CC -> 22 FC, 0 CC
7/5: 25 FC, 0.5 CC -> 24.5 FC, 0.25 CC

 

[IceShadow]

Now be sure to maintain FC per the FC/CYA Levels. I'd test daily for a while so you get a feel of how much to add, then once you have that sense of it, you can cut back to testing every 2-3 days instead and just add per what you normally do.

 

[bja1288]

I did a full set of tests just now and also brought it in to Leslie’s to double check. We mostly agreed on measurements. I thought that I would need muriatic acid but they said they don’t recommend that for vinyl pools and that I’d be better off just letting levels drift down since they didn’t have dry acid in stock. They measured TA 150 and pH 7.9 and I measured TA 130 and 8.2. What do you guys think?

 

[wireform]

I think it's time to rely on your own testing and stay out of the pool store. Pool store and TFP rarely agree.

 

[chazas]

I did a full set of tests just now and also brought it in to Leslie’s to double check. We mostly agreed on measurements. I thought that I would need muriatic acid but they said they don’t recommend that for vinyl pools and that I’d be better off just letting levels drift down since they didn’t have dry acid in stock. They measured TA 150 and pH 7.9 and I measured TA 130 and 8.2. What do you guys think?

I just read this thread, congrats on getting this far! I would completely ignore Leslie’s. You know how to test. I also would ignore their advice, I don’t have a vinyl liner but the official pool school instructions tell you to pour muriatic acid very slowly in front of a return and brush after. Can’t imagine that would cause a problem.

 

[HermanTX]

I did a full set of tests just now and also brought it in to Leslie’s to double check. We mostly agreed on measurements. I thought that I would need muriatic acid but they said they don’t recommend that for vinyl pools and that I’d be better off just letting levels drift down since they didn’t have dry acid in stock. They measured TA 150 and pH 7.9 and I measured TA 130 and 8.2. What do you guys think?

Believe in your own testing. Follow recommendations in PM to add MA to reduce pH. Suggest you avoid dry acid.
Read

Acid - Further Reading

www.troublefreepool.com

 

[jeffchap]

I'm more comfortable using MA over dry acid. The MA disperses almost instantly in the water whereas the dry granules can sink to the bottom and bleach your liner as they dissolve.

 

[bja1288]

I'm more comfortable using MA over dry acid. The MA disperses almost instantly in the water whereas the dry granules can sink to the bottom and bleach your liner as they dissolve.

Thanks, went ahead and bought 2 gal of MA, gloves, and goggles. Did a small application this morning and saw it drop from 8.2 to 7.9 as expected. Will keep testing every day to get a feel for it and see if I need to drop my TA to keep pH in check. I found that my slow pour directly into the pool gives me 12 oz per 30 seconds so I’m using that method to roughly measure it out.

 

[Steve-D]

^^^ What @HermanTX said... ^^^
MA is preferred over dry acid (the granules) as dry acid will add sulfates that can only be removed by draining and refilling. Dry acid isn't as big a problem for vinyl liner pools as it is for plaster (or pools with a SWG) but the sulfates can still create problems long term as they accumulate.

 

[bja1288]

I’m a little surprised at how much daily LC I’ve needed. My CYA is 50 so my recommended FC range is 4-8. I’ve been targeting 6ish FC just because it’s in the middle. When I test 24 hours after adding, it has been below 4 a few times. Is that acceptable or should I never allow it to dip below 4? I’d prefer to just target 4 every day to save LC, but not sure if that’s acceptable. It has been 95+ most days here in SW Missouri and my pool gets tons of sun so hopefully the FC loss can be explained by the weather.

 

[HermanTX]

Is that acceptable or should I never allow it to dip below 4? I’d prefer to just target 4 every day to save LC, but not sure if that’s acceptable.

The risk of that strategy is that you get algae. If you read some of the threads where people need to SLAM, they are putting in 3 gals of LC a day just to get rid of the algae. So saving a half gal today may require spending 3 gals tomorrow. So the old saying - you can pay the piper now or pay him later. The later also requires a lot of more effort by you to SLAM.