Chlorine/CYA Chart

Jul 30, 2014
3
Houston, TX
1st of all this is an awesome site. Wish I would have had it the last 10 years, but looking forward to better pool care for the next 10. I have a question about the Chlorine/CYA Chart. I understand the realtionship between CYA and the Minium FC and Target FC. I don't understand the Shock FC number and where it fits in the equation or chart. I have just refilled after an 80% drain to correct my CYA. Once I get everything balanced I will be using Borax. My question stems from trying to get my Chlorine right as easily and cheaply as possible without increasing my CYA too quickly. I am using an auto Chlorinator and I average 2 tabs per week. I also shock weekly (In the summer) with a cup on Cal-Hypo 73%. I just want to know more about when and if to shock, or what else I need to do.
 
Welcome to TFP!

The shock level in the chart is the level you should use if you need to take care of a problem with the pool. An algae bloom or some other contamination Lower chlorine levels are ineffective, and higher levels can damage equipment.

Most of us never shock our pools unless there is a problem.

No matter how you use pucks, your CYA will increase rapidly.
 
:wave: Welcome to TFP!!!

shock level is the FC level you need to maintain if the ShockLevelAndMAINTAIN Process is required.

If your water is clear and your CC are near zero and FC consumption seems normal, then there is no need for the "shock" cup of cal-hypo. As long as you maintain more than the minimum FC level for you CYA level, then the likelihood of a problem developing requiring a SLAM is very low.

Realize that the use of tablet is a bad idea in a pool where you live as the CYA will climb and then require you to replace water. Additionally, cal-hypo is a bad idea where you live due to your hard water and when CH gets too high, again you have to replace water.

Take a look at these Pool School articles to further your learning :goodjob:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool
 
Since you do not close your pool and usually are facing water restrictions, water replacement is clearly not desired. So, you should not be adding CH and CYA unnecessarily. Which means only using liquid chlorine / bleach.
 
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