Chlorine Lock

Kdl

New member
Jul 7, 2020
2
Colorado Springs, CO
Something is causing high demand for chlorine. My pool is about 15,000 gallons, vinyl liner. CYA is 30; TH is 250; PH 7.4; Alkalinity 120; TC 1; FC 0. Those readings were taken in the morning - 12 hours after adding 6 lbs. of cal hypo chlorine the evening before with the filter running continuously overnight. The water is clear, no sign whatsoever of algae. What's my next step? Should I try 10 lbs. tonight to break the "lock"?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,524
Laughlin, NV
Welcome to the forum!
You need to follow the SLAM Process. To do that, you need a proper test kit. What test kit are you using?
'Chlorine Lock' is a pool store term. It does not exist. It is an excuse.
Please fill out your signature as the information helps us help you.
I suggest you read ABC's of Pool Water Chemistry.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,421
Evans, Georgia
Stick to plain liquid chlorine or bleach. PLAIN!.....no additives to confuse the problem. Walmart 10% Pool Essentials Liquid Chlorine is a good choice.
Which test kit are you using?
Chlorine "lock" is a lie. Its usually either incredibly high CYA, or its algae.

Maddie :flower:
 

Kdl

New member
Jul 7, 2020
2
Colorado Springs, CO
I am using test strips and a test kit but the reagents are a couple years old so that concerns me. I do not have high CYA or algae - the water is very clear! I have read lots of comments and none speak to my issue. Maybe I should have used the phrase "chlorine demand"?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,915
San Dimas, CA (LA County)
You have algae. There's no other explanation.

Two things consume chlorine: sunlight and organics. You lost a bunch overnight. There was no sun. That rules out sunlight. Which leaves organics. It's not a bunch of soggy leaves in the bottom -- you say the water is clear. That leaves organics not visible (yet) to the naked eye - algae.

You just need to get high enough chlorine in the pool long enough to kill it all faster than it can reproduce. And that includes hunting it down in the hiding places like behind lights, inside ladders, and in the skimmer. How much bleach? It takes as much as it takes. The better job you do opening things up and scrubbing and brushing the walls, the faster it goes. We call it SLAM Process

It shouldn't take but a couple days; you're not starting out green, like most of these folks. Do what they did. Newer ones are in the back. Recovering my old inspirational links