Chlorine management

[Jeff11078]

I'm new to the site this year. My water seems to be in good shape, but I need to get a better feel for managing the chlorine level.
I have a New Water auto chlorinator with a variable setting that I can adjust from 0-10. I have it set at 5.
My CC is has been under 0.5 for a week, but the FC is dropping daily by 1 ppm per day (pear tree stems that I keep vacuuming out).
Today I have FC=1, CC=0. CYA =45. pH=7.5. TA=120. CH=150.
Looking at the chart, I should have added some liquid chlorine when the FC dropped to 3-4 based on the 45 CYA? But how much?
Since I didn't, and FC is now 1, do I need to SLAM?

 

[duraleigh]

Use PoolMath. it will tell you exactly how much to add to get back to a certain FC.

That said, are you chlorinating with pucks?

 

[tim5055]

Are you still adding chlorine pacs to the "New Water Chlorinator"?

According to the NEW WATER CYCLER PAC MSDS the pacs contain -"SYNONYMS -Trichloroisocyanuric Acid, TCCA, Trichlor, Trichloro- s-triazinetrione"

If you are still using them this is going to drive your CYA through the roof as Trichlor is almost half CYA.

With your current CYA of 50 (There is no 45 on the scale) your FC sholuld NEVER go below 4 and you should target 6 to keep it above 4 as the UV depletes the FC during the day.

You say the water "seems to be in good shape". Does this mean it's clear? Any visible algae?

We determine the need to SLAM a pool based on organics consuming the chlorine. Only two things cause a reduction of FC levels - UV form the sun and organics. So to see if there are organics consuming your chlorine we conduct an Overnight FC Loss Test (OCLT). With the pump running add sufficient liquid chlorine to bring your target of 6 and perform the OCLT after the sun sets. Remember, turn your auto-chlorinator off if it is still on when running this test.

 

[duraleigh]

If you are using the pucks (you should stop) then you can bring the FC back up by a specific dosage of liquid chlorine into your pool. You can manage your FC much more precisely with liquid chlorine and you can avoid over stabilizing by stopping the use of tri-chlor.