Testing results, need advice

[mer1844]

Ok, you need a proper drop-test kit because some of these numbers don't make sense, and I can see you are using test strips. Strips are a lousy alternative to drop-testing.

Here's a rule: TC =FC + CC.
If it doesn't something in your testing is wrong, by definition. If your FC is 1.5, and your CC is .5, then your TC is 2. If your TC reading is 3, then one of the 3 readings MUST be wrong, by definition.

Also, I noticed your CYA dropped from >100 to 40. That can ONLY be a testing error unless you replaced 60% of your water.

ASSUMING your FC and CC numbers are correct, and your CYA number is correct, you need chlorine for 2 reasons:
1) you need to shock out the CC so it goes to 0--raise FC to 15 to do this.
2) You need to never let FC go below 3 if your CYA is 40.

I use a PS233 Complete Swimming Pool Testkit from Pool Solutions that I purchased last summer. Not test strips. I follow the directions step by step as printed on the inside top cover of the kit.

As I stated in the post, when using the PS-200 OTO/Phenol red test kit, I have a hard time determining the exact colors of the lighter yellows for the chlorine readings, so the reading could very well be 2 instead of 3.

The CYA didn't drop from 100 to 40. It dropped from 45 to 40, but I did backwash and rinse the filter this morning, and then added water. This may account for the drop.

[CarlD]

I must have read something wrong...I thought I saw CYA >100...Sorry.

Still, TC = FC + CC. If you use the FAS-DPD test for chlorine you shouldn't use the TC test in the PS-200 portion--calculate TC by the formula. Usually, such discrepancies indicate a test strip...Another "Sorry!" from me.

My advice, though, hasn't changed:

1) you need to shock out the CC so it goes to 0--raise FC to 15 to do this.
2) You need to never let FC go below 3 if your CYA is 40.

.

With CYA of 40, you should use bleach or liquid chlorine for your chlorine and shocking and not tri-chlor tabs.

[mer1844]

Thanks, for your help.

[waterbear]

Also dump the N2. It really isn't doing anything and you are just wasting money on the cartridges for it!