Calcium Hardness Questions - Fiberglass Pools

[skillset]

I have a 10K gallon fiberglass pool. A couple of CH questions:

1) Is there a minimal level of CH for FIBERGLASS? In some of the stuff I've read, I read a minimum of 200 should be maintained so "pool equipment" is not damaged. I've never had an issue before, but just curious. I'm asking because I'd like to start using CalHypo once in awhile to get to shock level versus bleach.

2) I've had issues with the Taylor calcium test where the last reagent (R-0012) turns my pink solution clear (not blue). This happens with only 2 drops of R-0012 so I am assuming my current reading is 20. I read another post where it linked to the Taylor site and they suggest adding a few drops of R-0012 prior to second reagent. I did this, but then when adding the second reagent the liquid turned clear.

3) A few years back, I did add some Calcium. But, interestingly, when I added my usual dose of Metal Magic, I think it removed the Calcium from the water by filtering it. I remember I thought I wasted money on the Calcium! Since my pool requires about a quart of Metal Magic every 25 days (or else I get staining), seems like Calcium won't stay in the pool. Not that I'm worried because I've operated this pool for years using BBB without many issues. But, just wanted to see if this makes sense...

 

[linen]

1. Our recommended level is 220-320 ppm CH. See: http://www.troublefreepool.com/pool-school/recommended_levels My understanding is the claim that "it protects the gelcoat" on gelcoats with calcium carbonate filler. If you know your gel coat does not have that filler, then you should be able to ignore low CH.

2. Review the extended test kit directions and make sure you are doing it correctly. See: http://www.troublefreepool.com/extended-test-kit-directions-t25081.html#p206396 Are you using a speedstir? How old is your reagent?

3. I have not heard of metal magic removing calcium...so I can't answer you question.

 

[skillset]

Appreciate the response.

My reagent is old but I remember having the same result when I first got it. Appreciate the link. I see there is a recommendation of using distilled water, so I'll try that. Could be the calcium is just so low in the pool? I may try to mix some of the calcium I have with the pool water and see if I can simulate a better test where I get a blue endpoint. Not using a magnetic stir.

I am so used to testing the water before adding anything!

 

[linen]

If your calcium is 0 it should just turn blue. Is the dark blue reagent staining it's bottle? That is often a sign that the reagent has gone bad.

 

[toofast]

So to add to this thread, I received this "response" from the MFG of my Fiberglass shell.

Good to hear from you. Congratulations.
Our gelcoat does not have the calcium carbonate filler.
Please check with your dealer for his recommendations though... I think the numbers I hear is that you want the CH between 200 & 400. Too low and the water is corrosive, too high and you get scalling. I think what you might be referring to regarding "it protects the gelcoat" on gelcoats with calcium carbonate filler is that the pool chemistry always tries to balance. If there is too much hardness in the water it will build up on the pool, if there is too much hardness (calcium carbonate) in the pool it will try to dissolve into the water. (staining and blistering are the result). It is cheaper to manufacturer gel coat with calcium carbonate. I am sure you are aware that is what a supprising number of pools are manufactured with. We do not, we use an NPG/ISO. Of course it is more expensive, but gives you a greater insurance to not stain or blister. Please call me any time if you want to discuss more.

With that said, is it still a good idea to get my CH level up to 220 or can I truly ignore this due to my setup. If it will help with any other components, then for sure I want to make sure I am not compromising.

Thanks much!

 

[chem geek]

With no calcium carbonate filler and not other exposed plaster or grout in tile, you can ignore the CH at least as far as it being low. Obviously, if it gets too high then you can get scaling. As for protecting equipment or metal corrosion, that's not true -- the pH level and other factors are far more important.

So if you want, you can use Cal-Hypo as a source of chlorine since it will take a while to build up the CH. For every 10 ppm FC added by Cal-Hypo, it also increases CH by at least 7 ppm.

As for metal sequestrants, they also bind to calcium but usually don't have a noticeable effect unless you overdose on the metal sequestrant.

 

[toofast]

Thanks for the response....since I am using a Stenner Injection system for my "chlorine" I think my CH will most likely stay around 100, which is what it is now. I do have tile, but silicon grout.

However you did mention something, "far more important" - if I have OCD and I do , and everything else is in perfect balance - would increasing my CH to say the minimal level on the range help ANYWHERE ? Or am I just being silly and wasting money.

 

[chem geek]

The only other benefit to a higher CH level is in preventing foaming, mostly in spas, but that level is around 120-150 ppm. In pools, I don't see any benefit to having CH unless needed to protect plaster/grout surfaces (or calcium carbonate in the gelcoat of some fiberglass pools). I suppose if you had a waterfall or spillover and was getting foaming, then the CH could be somewhat increased. If added in pools that don't need it, it's an extra unneeded expense.

 

[toofast]

I just wanted to update this thread...2 years later my CH is 60 - assuming our thinking has not changed and that is OK.

HOWEVER, this does cause a CSI number for me of -0.87

I assume that is still ok, based on the pool type that I have...or do I need to worry about CSI (think I read I don't but want to make 100% sure)

 

[JasonLion]

CH levels around 200 can help reduce metal stains on fiberglass, if that is an issue for you. Otherwise, you should be fine where you are.