I think you can test for PHMB, but I don't really see that it matters. I converted my pool last summer from Baq to Cl. It was just a matter of holding the CL at some very large number (25 or 30?) for days on end. You have to check and add more CL 2 or three times a day, run your pump 24/7 and backwash a LOT. You want to get your pool clear and clean and sparkly, but you also want it to hold residual CL for 48 hours.