High combined chlorine

[RK23]

I am using a Taylor kit to test my water once or twice a week.  I typically don't have much combined chlorine, but this morning it registered at about 4 ppm while the FC was only 1 ppm.  Could this be a correct reading?  If so, how much dichlor would i need to shock this 500 gallon tub to rid the CC?

Thanks,
Russ

[Chad]

Russ, it's very unlikely that your CC is that high. Did you recently add some mps to your spa? I'm asking this because mps will register as CC on the Taylor chlorine test.

[RK23]

Hi Chad,

Yes, added MPS yesterday evening and ran with cover off for 30 mins.  Had several bathers in before that, and had gotten FC to about 3ppm with dichlor an hour before they bathed.

Also, have ozonator and N2, in case that matters.  I will test again later tonight and post back in am if still having an issue.

Thanks.