No need to be sorry, it IS a simple problem and we both agree that "something is consuming your chlorine."

I was simply sharing my situation relative to phosphate buildup that I've experienced several times in the last 9-10 years of pool ownership. I could have shocked for weeks and the problem wouldn't have gone away. Like vanman, I was unable to maintain chlorine leve within the pool. And this situation repeated itself AFTER installing a SWG (chlorine level 100ppm within the cell) virtually eliminating routine shocking.

Your assertion that "you have absolutely NO reason to suspect or treat phosphates" is not clear for me, considering I advised he 'might have his phosphates checked", and it's exactly what I've experienced with my own pool the last decade.

Given my history, what harm could be done by a free phosphate test?