Tile grout and other cement products tend to be basic (high pH) not acidic (low pH). If you can ID the grout used, it shouldn't be hard to determine whether that particular grout is acidic for some strange reason.

But my guess is the service company is BS'ing you because they might otherwise be on the hook for an expensive heater. To kill a heater in 6 weeks, the pH has to be REALLY really low.

By the way, low pH ALSO damages concrete . . . and tile grout!

I'd *strongly* recommend that you do 2 things:

1. Go purchase a cheap OTO / phenol red drops kit (Walmart, etc) TODAY. Test and post your results.

2. Order a K2006 kit, so you can get accurate results yourself. If you have had pH low enough to destroy a heater in 6 weeks, you have had SERIOUS chemical problems that your chemical company should have noticed REGARDLESS of the source of the low pH http://pool9.net/tk/