Closing chemistry recommendation

[JimK]

So here's how I'm reading the info in this thread-

You bring you water to shock level to clear it.

You wait some amount of time and then add polyquat

You wait a little longer and then raise your FC again and close.

The problem I see is that, based on the manufacturers recommended process, if you follow the CYA/FC relationship (as you should) then your shock level of FC is definitely going to cleave the PQ into smaller subunits unless you wait long enough after shock level for the FC to drop below 10ppm. If you look carefully at what the manufacturer says, they say to shock up to 5-10ppm and then "wait a few days" before adding the PQ. That tells me that the PQ is definitely going to cleave.

I guess the ultimate question is, at what FC does PQ start to cleave into smaller fragments and at what FC is the PQ's algaestatic properties completely destroyed? That last part would set the upper bound of how much FC you can have in the water when you add the PQ. Add the PQ too soon after raising the FC to shock level and you risk the chlorine burning up all your PQ.

Interesting stuff here.....

I was wondering about that also.