Converting to liquid chlorine - should I SLAM to get started

svierregger

Member
Sep 28, 2011
15
I have an in-ground plaster pool and until recently have been using a Hayward offline chlorine tablet system. I was vaguely aware of CYA and knew it was elevated due to my use of stabilized tablets. About a week ago I did a CYA test using a new Taylor 2006 kit and it was reading in the 150 range. I bit the bullet and drained about 25k gallons from the pool to lower it since the standard 18" draining in the fall wasn't significantly lowering the CYA. I left several feet of water in the deep and a few feet in the spa then refilled. I was surprised that after adding 25k gallons of fresh water that my CYA is still 45-55 or so depending on how my eyes are working with that darn black dot. I decided to leave the CYA problem behind and jump with both feet into the TroubleFreePool and start using liquid bleach/pool shock. I ordered a Stenner 45MP2 but in the meantime I'm using the mobile app to track my testing and add chlorine manually.

I picked up my first liquid shock at a pool supply store. It was an off-brand called Shock It 12.5%. The box had a Julian date of May but when I opened the box at home the containers had a Julian date of late February. I went through 6 of the 8 gallons and bounced between 0-2.5 ppm FC, testing daily. I don't think the advertised 12.5% was still 12.5%. I've moved on to Lowe's Pool Essentials 10% dated May 2020 on the jugs. My FC was 2.5 this morning after using a bit more than a gallon yesterday (FC was 2.5 yesterday morning). It was sunny and hot yesterday and we got .5 inches of rain or so overnight.

The app says my target FC is 7, but adding a gallon give or take each day doesn't seem to be getting me there. There is a toggle button for SLAM in the app, and that recommends adding 5 gallons or so to take me to 22 ppm. Is it recommended to SLAM, then manage the FC on it's way back down? I'll do that if it gets me over the hump and helps me maintain my daily chlorine usage at a more reasonable level.

For reference, my test figures this morning were:

FC 2.5
CC 0
PH 7.6
TA 80
CH 290 (I'm waiting on 40 pounds of calcium chloride to arrive)
CYA 50 ish
CSI -.1
Water temp 81

And the app had me add 153 oz of 10% liquid shock.

Thanks!
 

splashpad

Bronze Supporter
Aug 2, 2017
2,712
SE Kansas!
Welcome back to the forums!

Do you have cloudiness, or only concerns that the FC isn't holding?

When there is a question of CYA level, always go with the higher 10, so I would call your CYA/60. (To recheck CYA, you can pour the mixture back into the bottle and then fill the tube to the first line, glance for dot, see dot? Fill to next line, etc. Until when you glance you don't see the dot. Don't stare into the tube. Be sure it's bright, preferrably sunny with the sun at your back.) CYA - Cyanuric Acid Test - Trouble Free Pool

I would suggest to try this, with the pump running, use PoolMath to add enough chlorine to raise your FC/24 (SLAM level for CYA/60) recheck in 15-30min. If you have lost any, you will probably be looking at a SLAM Process, which will be maintaining FC/24 with CYA/60 until the FC holds overnight. You could also look into a partial drain again to lower the CYA further, to make the SLAM FC level more manageable.
 

svierregger

Member
Sep 28, 2011
15
Welcome back to the forums!

Do you have cloudiness, or only concerns that the FC isn't holding?

When there is a question of CYA level, always go with the higher 10, so I would call your CYA/60. (To recheck CYA, you can pour the mixture back into the bottle and then fill the tube to the first line, glance for dot, see dot? Fill to next line, etc. Until when you glance you don't see the dot. Don't stare into the tube. Be sure it's bright, preferrably sunny with the sun at your back.) CYA - Cyanuric Acid Test - Trouble Free Pool

I would suggest to try this, with the pump running, use PoolMath to add enough chlorine to raise your FC/24 (SLAM level for CYA/60) recheck in 15-30min. If you have lost any, you will probably be looking at a SLAM Process, which will be maintaining FC/24 with CYA/60 until the FC holds overnight. You could also look into a partial drain again to lower the CYA further, to make the SLAM FC level more manageable.

Thanks for the info. I have been pouring the LC out of a one gallon measuring pitcher by walking around the perimeter of the pool. Is that a good idea or should I drop 5 gallons in the deep end where there is a skimmer and the main drains? Is 15-30 minutes enough to disperse the 5 gallons of LC so I can get an accurate test reading? And should I take that 15-30 minute reading away from where I dropped the LC into the pool? Since I added the 153 oz an hour or two ago, I think I will add the balance of the SLAM recommendation or 4 gallons give or take.
 
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splashpad

Bronze Supporter
Aug 2, 2017
2,712
SE Kansas!
Thanks for the info. I have been pouring the LC out of a one gallon measuring pitcher by walking around the perimeter of the pool.
That can work, we usually suggest to pour it slowly in-front of a return (with pump running) as it's sure to get mixed in and "diluted" properly.

Is that a good idea or should I drop 5 gallons in the deep end where there is a skimmer and the main drains?
Definitely do not pour it where it has the chance to go through equipment mostly undiluted. You want the chlorine in the pool water, not your equipment ;)

Is 15-30 minutes enough to disperse the 5 gallons of LC so I can get an accurate test reading? And should I take that 15-30 minute reading away from where I dropped the LC into the pool? Since I added the 153 oz an hour or two ago, I think I will add the balance of the SLAM recommendation or 4 gallons give or take.
Definitely test away from the area where it is added. Sounds good! Hoping you get a good reading!
 

Stenner Tech Support

In The Industry
Apr 14, 2020
66
Florida
Hi,

Thank you for choosing Stenner Pumps for your application. We are attaching the Basic Service Manual, and if you have any questions, please feel free to contact us here.
 

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