I've been using bleach to chlorinate our new plaster pool for the last couple of months after reading Pool School on this site. The pool looks great and it seems to be working fine.

My pool builder came out today to fix a broken cover and saw my stash of empty clorox bottles in the pool house. He told me that using bleach was the worst thing I could do for my plaster. He said that it contains metals that will stain the surface and I should be using Cal-hypo granules instead like he told me originally. He said that if I strain some bleach through a white cloth I'll see the metal stains that it leaves on the cloth. I do have a few brown stains on the plaster. Is there any truth to this? Could it be caused by using bleach and should I switch to Cal-hypo? I also asked him about Cal-hypo increasing the water's calcium levels and he said that that wasn't a problem.

He also said that using bleach will cause the water to release gasses that will ruin my auto-cover. He said the bleach gasses would turn it brittle and make it crack. He said Cal-hypo won't do this. Any possible truth to this?

Nope, nope, and nope. Bleach will not cause any issues with stains, covers, etc. Chlorine is chlorine!

Can you post pictures of the brown areas of the plaster? How new is it?

It's amazing the things that so called professionals pass on as gospel. Bleach is safer than any other type of chorine you can use.

I don't know where you're located but there are tons of folks in high hardness areas that would fight him for even suggesting that Cal-Hypo isn't a problem.

Chlorine from bleach doesn't outgass anything that every other source of chlorine doesn't outgass.

As far as metals go, once the chems enter the bleach process it's all either all titanium or plastic lined piping and equipment.

Ditto to what these guys said. Ask him if he will guarantee your pool surface against calcium scalling if you switch to calhypo? Also, ask him to provide you proof that bleach contains metals.

I bet he doesn't sell liquid chlorine. IME, the ones who don't sell it, are the ones who won't recommend it.

clorox is chlorine - read the label. I've used chlorine for 1 year on my plaster pool. No evidence of any brown stains... Ask him what he thinks of an SWG. My guess is he will not recommend that either.

He hasn't the faintest idea what he's talking about. Cal-hypo does everything bleach does (since it's bleach plus calcium), and it doesn't do any of the stuff claimed.

Metals in even small quantities in chlorinating liquid or bleach would lead to fairly rapid degradation of the chlorine (see this link, for example). The ingredients in Clorox Bleach and other grocery/hardware store products are described in this post.