What is CH target for fiberglass pool?

[Maestro]

I've been testing and adjusting my water for one week now (brand new pool and brand new owner!). Thanks to this site, I'm happier with the numbers every day!

My latest question is, what should be my CH target number be for a fiberglass pool? Mine right now is very low, and PoolMath is recommending I add 48 pounds of calcium chloride to get to 260 ppm. That seems a bit drastic to me, so I'd like to get some advice before putting that much in. I understand how important it would be if I had a concrete pool, but do I have to go that high for fiberglass?

Here are my numbers today:
temp 84°
FC 4
CC 0
pH 7.5
CH 25
TA 110
CYA 20
CSI -0.83

I just put in bleach and stabilizer yesterday, so I expect the CYA to rise over the next few days. It's been 0, so I saw the dot disappear for the first time today!

 

[ewkearns]

http://www.troublefreepool.com/content/134-recommended-levels

 

[Maestro]

Ok then, 48 pounds it is! I think I'll put in half today and test tomorrow to see where I am. Luckily I have a lead on a 50 lb. bag at a local pool store.

What would be the negative consequences to having very low CH in a fiberglass pool?

 

[Maestro]

Also, I scatter this across the surface of the deep end, right? Should I shut off the main drains and let everything go through the skimmer? Or will some of the calcium sink and get picked up by the main drains?

 

[ewkearns]

What I always do is pre-dissolve the calcium in a bucket of water and then slowly pour it in the turbulent water at the return in the deep end.... at least that is what the PB advised me to do. Bear in mind that the calcium chloride, when mixed with water, is going to get HOT, so take it a little easy and make a few pours of less CC, rather than one scary big one....

 

[Maestro]

Okay, thanks. Should I avoid swimming until the CC is absorbed? Is that less than an hour or more like overnight?

 

[borjis]

Fiberglass & Vinyl liner pools don't require calcium.

It won't hurt anything to have it but it's not required as it is in concrete / gunite pools.

 

[YippeeSkippy]

I *think* the explanation is that no one knows if the fiberglass pool company used calcium in their construction. If they did you'd want to have some in there to prevent it from leaching out into the water (like its seeking equilibrium or something?) so having some there covers all bases.

It isn't always required, but doesn't hurt either....just in case. That's my story and I'm sticking to it

 

[borjis]

Didn't know fiberglass pools were built with calcium in them.

I would figure the gel coating itself would not either, but better safe than sorry i guess.