Hi Ben,

Thank you for the reply and all the helpful information. I forgot to mention earlier that the acid pump has been disconnected for about a year now so I know for certain that the pump is not "secretly" adding acid to the pool. The pool manufacturer is puzzled because he says that normally pH will always drift up and not down. He said it had something to do with the "leaching" of the marcite. As far as "tricking" the system by putting a "Normally Closed" switch on the system, I don't understand how that would work because when the pH sensor senses that the pool needs acid, the acid pump does not continuously stay on, rather, it cycles on and off a few minutes at a time over a period of about an hour or so. Regarding the "switchable pH control circuit", I think that is an excellent idea and I have already contacted the manufacturer to see what they say about that. Thanks Again!