I have never used it myself, but as mentioned by Chicki, you guys may be interested in the thread on RC, in the Chemistry forum. Randy has some comments on the Canadian version. As a matter of fact he says do not use it. Is that the same product?

Brad,

Just pulling at strings here but with the colder weather is your furnace on and windows closed?

Doug, you may be referring to my recent thread with Randy. The surfactant is added to the VIP brand, according to the manufacturer. Arm&Hammer did not return my email. Randy had made a joke about Canadian soda, not realizing that in fact there is a difference.

Jamie, at this point it looks like a drifting pH probe, rather than a real pH problem. And no, the windows are still open (to my family's dismay) and I have electric heat.