Calcium hardness and fiberglass pools

[aguaguy]

I have a small (7000 gallon) fiberglass pool with sparkling clear water using BBB method

FAC 5
PH 7.6
TA 80
CH 120
CYA 50

Went to Leslie's today to get the water tested to for the first time this season (Northern Ca) and he wants me to add 6 lbs of hardness plus. From what I have read I need not do this.

I would appreciate feedback to further my knowledge.

[aylad]

He wants you to do that because the markup on calcium flakes is apparently pretty good. Don't worry about it.

Janet

[mbar]

I like to keep some calcium in my fiberglass pool, I usually keep it at around 125 - 150. Some say calcium is not needed for fiberglass pools, but some manufacturers say it is needed for the gelcoat. I don't know what is really true, so I just keep it low. I get it by using the cal hypo shock. So if it were my pool I wouldn't add any more, especially since your water is beautiful!

[chem geek]

From what I've read, some gelcoats have a calcium carbonate "backing" so if that's the case then it would make logical sense to have some calcium in the water, just in case.

Richard

[waterbear]

The calcium is supposed to help prevent staining and to prevent cobalt leaching from the gelcoat. Cobalt staining is very common in fiberglass pools and looks like little black dots that seem to grow like a crystal. I keep mine at about 250 ppm. I used to keep it lower but I had iron stains more often. Since I increased the hardness of the water I have had much less iron staining in the pool.Didn't even need to use any ascorbic acid this year!