Reynbob Posted October 29, 2014 Report Share Posted October 29, 2014 Long time forum follower....new registered user. I own and operate a small town retail pool store and have been following the advisement of the water-wizards on this forum for some time. Including the advisement about calcium hardness in fiberglass and vinyl pools. In other words...not really necessary. For back ground, one rural water provider in this area has very soft water....in the 12-20ppm CH range....very soft....Our chemical supplier is insisting on the need for calcium hardness in the standard range that most water testing applications ask when testing fiberglass and vinyl pools. He went so far as to state that low CH could or might crack a fiberglass pool. I do understand the need in plaster pools and I do follow NPC guidelines on new turn-ups...or as closely as practical considering they were drafted by a "committee". I would like to know if standard fiberglass/vinyl CH levels are indeed absolutely necessary or not. I trust you guys and I want to do the right thing for my customers. Please advise and thanks in advance. Quote Link to comment Share on other sites More sharing options...
chem geek Posted October 29, 2014 Report Share Posted October 29, 2014 For vinyl, you can read more in this post where basically it would only be helpful when the calcium carbonate filler in vinyl exceeded 7% by weight, but generally vinyl is of higher quality and the CH is not needed. There have been tens of thousands of vinyl pool owners reporting in on multiple forums over more than a decade and there have not been any problem from low or no CH in such pools. The UV in sunlight is the most destructive to vinyl though obviously adding concentrated acid quickly without good circulation is not good since it can pool (that would be bad for all surfaces.Some CH can be helpful in preventing cobalt and iron staining (see this post), but the main reason for some CH in fiberglass pools is to protect the gelcoat that may contain calcium carbonate. Not all gelcoat contains calcium carbonate so the real answer is "it depends" so to play it safe some CH is reasonable. If you know that your gelcoat does not contain calcium carbonate, then you shouldn't need CH. See this post for an example response from a manufacturer. Quote Link to comment Share on other sites More sharing options...
Reynbob Posted October 29, 2014 Author Report Share Posted October 29, 2014 Thanks for the quick response Chem Geek....I would suppose being better safe than sorry would be appropriate for fiberglass pools....unless the pool owners knew the composition of their shell or were so inclined to find out. In most cases I doubt this would be the case. I also noted that there was no link on the see-this-post on your vinyl liner response....I would be interested to see that also please. Thanks again for the response.... Quote Link to comment Share on other sites More sharing options...
chem geek Posted October 30, 2014 Report Share Posted October 30, 2014 I've edited the post to add the link. Thanks for catching that. Quote Link to comment Share on other sites More sharing options...
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