Any problem with pool shock that sits on bottom of a plaster pool?

[Tom007]

I am following the BBB method, but using Cal Hypo shock instead of liquid bleach. The Cal Hypo is a little cheaper and a little easier to use than bleach, and it is not raising the calcium level in the pool.

Is there any problem when the shock sits on the bottom of the pool and doesn't dissolve immediately? This is a plaster pool.

[nefretrameses]

I used cal hypo in my plaster pool for awhile because I needed to raise my calcium. I have a 50 pound container that I used about 5 pounds of to raise CH by 50 ppm.Your description is confusing. I can't understand how you can not raise calcium I f you are using cal hypo. How are you testing? Test strips or a good drop based test? How are you adding the cal hypo? Broadcasting onto the surface, through the skimmer? What kind of filter?

[Tom007]

I can't understand how you can not raise calcium I f you are using cal hypo.

I don't understand it either. I used a good drop test kit. Maybe the calcium was low to start with. I should probably test it more often, and plan to do that next year. For now it is getting cold and I won't be using the pool or adding chlorine.

Doesn't calcium naturally go down over time?

I added the cal hypo by broadcasting it on the surface. I have a sand filter.

My big question is about what happens when it sinks to the bottom and sits there for a while before dissolving. Does it do any harm to a plaster pool?

I

[chem geek]

The calcium does not disappear on its own. It is lowered through water dilution so rain overflow or significant backwashing. Evaporation and refill will only increase it by the CH that is in the fill water since calcium is not volatile.

As for sitting on the bottom of a plaster pool, calcium hypochlorite is not acidic (like Trichlor pucks) which would otherwise be detrimental to plaster, but the concentrated chlorine might be a problem for colored plaster. For white plaster, it's probably OK, but I'd try brushing it to mix it up after adding it or you can try pre-dissolving it in a large bucket first.

[nefretrameses]

If you leave your pool open all year like we do, I'd get my calcium within the proper range and monitor pH all winter. I made the mistake of having low CH and low pH last winter and it was too aggresive for my finish. I found particles from my finish coming loose and it continued for several months after getting the water balanced. I'd keep enough chlorine to prevent algae unless you are "closing" your pool.

[CarlD]

If the cal-hypo is not raising the calcium levels in your pool there aren't really many reasons why. Here's what I think they are:
1) You could be losing water and constantly adding more, as Chem_Geek pointed out.
2) Your reagents are old and not effective and need to be replaced
3) You are running the test incorrectly
4) You are testing with strips which are VERY difficult to infer exact values from (I find them worthless for CH and TA)
5) You simply aren't using enough Cal-Hypo and calcium isn't effectively increasing.
6) You are wasting your money on the 48% stuff instead of the 62-68%. WalMart pushes that junk instead of the good stuff. It only SEEMS cheaper.

[Tom007]

1) You could be losing water and constantly adding more, as Chem_Geek pointed out.

I lose water to evaporation, which should not effect chemical levels. I lose some water when I backwash. I lose some when a heavy rain raises the water level above the drain. I am pretty sure there is no leak.


2) Your reagents are old and not effective and need to be replaced
3) You are running the test incorrectly
4) You are testing with strips which are VERY difficult to infer exact values from (I find them worthless for CH and TA)


I think I am running the test correctly, with good reagents, because the pool store, which is also doing the drop test, gets the same results. How long do the reagents stay good?


5) You simply aren't using enough Cal-Hypo and calcium isn't effectively increasing.

My guess it that this is what is happening. I used about 50 lbs in my 22,000 gallon pool over the summer. Does anyone know how much calcium is in a pound of 68% cal hypo?


6) You are wasting your money on the 48% stuff instead of the 62-68%. WalMart pushes that junk instead of the good stuff. It only SEEMS cheaper.

This is the stuff I am using. It is 68%. Amazon delivers it, and is the cheapest place I have found.
http://www.amazon.com/gp/product/B003BPNHV0/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
It ends up being a little cheaper than liquid chlorine bleach, and easier to use.

[Tom007]

To the moderator - When will I get full privileges here? I have been here well over a month. I have posted questions and answered questions. I think I have been a polite and helpful member.

[nefretrameses]

After you get the stuff on the bottom dissolved, recheck you CH. I've read how you can minimize the amount of calcium added to a pool but mixing cal-hypo in a bucket of pool water and pouring it into the pool until you start getting some slurry. Mix it again and pour again until you get slurry, then toss the rest. I guess the calcium dissolves slower than the "hypo". Maybe that's what's on the bottom of your pool - or other unknown stuff like CarlD describes in "cheap" products.

[CarlD]

Tom, I just gave you what I think are reasonable alternatives to explain your problem. If you and the pool store are getting similar results then you are probably running the test correctly. You can always put a handful of the cal hypo in a couple of gallons of water and see if you get really, really high results when you run the test. If you still get "zero" you're doing something wrong or have bad reagents.

[BigDave]

50 lbs in 22,000 gallons should raise the calcium by more than 100 - this should be visible on the test.

Ben describes a method of dosing cal-Hypo designed to prevent buildup for pools with sand filters. Dosing cal-hypo through the skimmer and letting it dissolve on the sand bed encourages the calcium to precipitate out onto the filter. This acts as a filter aid and can help keep some of the calcium out of solution. I can anecdotally confirm this as I used this method for the last half of last season; I didn't measure an increase in calcium (only tested twice), I did find fine white material (finer than sand) on backwash. Warning! cal-hypo must never be put in the skimmer if there's any chance that any stabilized chlorine could be in the circulation system - this can cause an explosion.