3 week SLAM crystal clear water but FC loss where??

[Bperry]

I was assuming to have a reading of 12 ppm first thing in the morning after adding the suggested amount to reach 12. I did the overnight test with out adding chlorine last night and only lost 1 ppm!!! Now I most go find my next steps. Thanks for helping me thru the process.

Are you adding chlorine at night and then not testing 30 minutes later? If so, that’s a problem. The poolmath estimation isn’t an exact thing and so you can’t just add what it takes to get to 12 and assume it’s accurate.

You always test AFTER adding chlorine, not before.

 

[PoolStored]

You always test AFTER adding chlorine, not before.

You always test AFTER adding chlorine [for the OCLT test, and you should let it circulate 30 minutes before testing], notl [as well as] before [so you know how much to add].

 

[agail4]

You always test AFTER adding chlorine [for the OCLT test, and you should let it circulate 30 minutes before testing], notl [as well as] before [so you know how much to add].

This is perfect instructions!

 

[PoolStored]

This is perfect instructions!

Cleaned up...

Test your FC and make your last addition for the night to get to target. Run the pump for 30 minutes. Make sure it is after sunset, then test. This is starting FC for OCLT.
In the morning, run the pump for at least 30 minutes and test before sunrise. This is ending FC for OCLT.

 

[Bperry]

You always test AFTER adding chlorine [for the OCLT test, and you should let it circulate 30 minutes before testing], notl [as well as] before [so you know how much to add].

That’s a good clarification. No harm in testing beforehand if you’re doing a SLAM anyway. (Sometimes I do an OCLT when I’m not adding any chlorine beforehand). The point of the OCLT is to know -exactly- what the chlorine level is at night and again exactly what it is in the morning. No estimates.