Hi Carl,

Thanks for the reply, and great feedback. So, what are we supposed to do? The heater manufacturers all give you the levels they want you to have, and NONE of them tell you to have a FC level above 3. Yet, they do recommend CYA at, I believe, 70. And, going off Ben's guide, a CYA of 70 equates to an FC level of between 5 and 10. If a manufacturer saw that you had those levels, they would immediately point to the water being too corrosive. Plus, and I'd have to go look at the "wheel", but I think that would create other problems when looking at Taylor's water balance wheel?

My pH has continued to rise even after I stopped using the SWG, to my surprise. Not really sure why that would be. Regarding your concern of the acid feeder, I have to dilute the acid in the tank anyway so that the pool pH stays consistent. Plus, it feeds just outside of the filter tank on the return to the pool, so the higher acid level in the tank gets diluted before it returns to the heaters (i.e. only pool water hits the heaters). Plus, we had a majority of our heater failures before we put the acid feeder in. I only put the acid feeder in for convenience and to try to maintain a more consistent pH, rather than adding multiple cups every day or two.

So, maybe, from your feedback, the question is: by following the manufacturer recommended chemistry levels, am I actually creating the problem? I'm not a chemist, but intuitively, it seems to me like having higher FC, lower TA, and higher CYA would make the water more corrosive to heaters?

Ben, I'll try and get photos of the heat exchangers when the tech brings them back. He was going to call Raypak to talk to them, and then ship them back using the boxes from the new exchangers, which are at my house....

By the way, Ben, for flow-purposes, I have 3 skimmers, and two main-drains. The pool is only 6.5 feet at its deepest (not sure if that makes any difference).