Actually, according to two different engineers -- 10+ years apart -- at Canadian General, the calcium content is mostly irrelevant. But, the swelling at low pH is consistent from all sources.

However, what you are saying about chlorine penetrating is also contradicted by all vinyl engineers I've spoken with -- the consensus I've encountered is that chlorine at pool levels (<100ppm) doesn't affect the vinyl sheeting, but CAN damage the printed patterns, and some dyes, especially medium blue.

Also, the article refers to a study, but doesn't cite it or state when and where it took place nor who conducted it. Nor is there any bio or CV info on "Donald Redpath". The article reads much like one of the "expert" articles from Service Industry News . . . and those aren't entirely trustworthy.

So, unless there's better info, I'm going to stick with the info Chem_Geek and I have been given by vinyl sheet mfg engineers.

Ben