PolyQuat and Shocking with Chlorine

[chem geek]

Carl,

You mentioned in this post how large quantities of polyquat consume large quantities of chlorine (or vice versa) and others have reported the same sort of thing when they close their pools using high doses of both polyquat and chlorine.

I'd like to try and figure out what's going on so that we aren't doing something stupid. If you or anyone plans to close their pool this season with high doses of polyquat and chlorine and notice the chlorine (FC) level drop considerably, check on the combined chlorine (CC) level (by measuring total chlorine, TC) to see if it has gone up.

If the chlorine combines with PolyQuat to form a chlorinated PolyQuat, this should show up as a combined chlorine and perhaps it continues to be effective as an algicide in this form. However, eventually, it may break down (get oxidized) and not show up in CC and not be effective.

Just wondering if we are fooling ourselves thinking that we can close a pool with high chlorine and PolyQuat levels simultaneously. The fact that it is recommended that PolyQuat be added on a regular basis may mean that it gets broken down, though slowly under normal chlorine levels. Or it may mean that manufacturers just want us to use more and don't care about buildup (ya think!).

Richard