cal-hypo to raise CH

[beezar]

Hi, my calcium hardness level appears to be low for my plaster pool, but CSI seems to be ok.

Numbers:
pH 7.8
TA 130
CH 140
CYA 70
temp 60 deg

CSI turns out to be -0.05. I have a 4500 gallon spa with a plaster surface.

Some questions:

1) Is it essential to raise CH levels if my CSI appears ok?
2) lf I wanted to raise CH, can I just use cal-hypo tabs to do this which will reduce the amount of bleach I have to add as well?
3) How long will it take for the cal-hypo tabs before CH level is appropriate?
4) Also, I've read dissolving cal-hypo in a bucket then pouring it in, but can I instead use one of those pool floaters and just place some tabs in there to distribute the cal-hypo slowly?

Thanks!

 

[Guest]

Calcium is critical to plaster, and you should be between 200-400 ppm calcium. I don't see a calcium reading in your specs, but I assume you know what it is.

Why not just get some calcium chloride if you need to raise the CH? It is cheap and you don't have to add all that other stuff or guess how much you need.

 

[chem geek]

You do not need to raise your CH level. It is calcium carbonate saturation (which is what the CSI calculates) that is important for plaster, not calcium alone at any particular level. Not only is the CSI what is important, but even then you only need to be in the ballpark with it. Your higher pH and TA levels are currently compensating for the lower CH. So long as your pH isn't rising too quickly from the higher TA, then what you've got is fine. If at your next water drain/refill (for a spa) or in the summer you end up lowering your TA substantially and target a lower pH, then you could consider increasing the pH, but I wouldn't worry about this now.

Yes you could just use Cal-Hypo as your source of chlorine in order to raise the CH level in the future if you need/want to do that. For every 10 ppm Free Chlorine (FC) added by Cal-Hypo, it will increase your CH by around 7 ppm so you can figure how long it will take based on your chlorine usage.

Cal-Hypo tends to dissolve too quickly and needs a special type of chlorinator for that purpose. You most certainly do not want to put it into a standard floating chlorinator or inline chlorinator that has had Trichlor in it, ever, because the two can cause an explosion or fire (see this link for a video).

 

[beezar]

Thanks for the tips. That video of the cal-hypo and trichlor explosion is crazy! I can see a lot of novices such as myself making this mistake considering they are both chlorine sources...

what's the best way to add cal-hypo to a 4500 gallon spa like mine by the way?

 

[guamguy]

I usually pre-dissolve the amount I want to add in a bucket of water, then slowly pour in over a return

 

[JasonLion]

Keep in mind that cal-hypo gets really hot while it is dissolving. If you dissolve too much at once you can get burned, or melt the bucket. This isn't normally a problem, just something to be aware of.