Chlorine drop to ~0 ppm after calcium addition. UPDATE: Now with controlled test.

[Brian PacNW]

I wanted to bump up my calcium by about 80 or 100 ppm. I did so late at night, several hours after topping off the chlorine to 6 ppm. In the morning the FC was essentially 0 ppm. I added enough liquid chlorine to bring it back up to 6 ppm, then a few hours later it was around 1 ppm. Finally after a 'standard' shock (SL without the AM) things seem to be back to normal.

We did have ~5 kids in the 3800 gal pool that day before I topped off the FC, so I assumed it was some type of mass urination event, even though these same kids have been in there a couple times without any prior problems with the FC. Then after searching the forums I see that I am not alone in this experience. Might have be the calcium, possibly contaminated with organics.

I have plenty of the suspect chemical left in the bag. I might do a mini controlled experiment on some water in two buckets, one with a fresh dose of calcium, to see if the FC drops overnight in that one.

Anyway, I don't have any real questions about it. Just documenting & sharing here.

UPDATE: See post #29 for my controlled test

 

[Jimrahbe]

Brian,

I don't understand how adding Calcium to your pool would effect your FC.. at all???

But, let's ask someone that actually knows how to spell Khemistry.. Calling @JoyfulNoise

Thanks,

Jim R.

 

[Brian PacNW]

@Jimrahbe I don't understand it either. I believe others were thinking contamination possibly. I found other examples here, here, and here, for example

 

[duraleigh]

Adding CH has no measurable effect on FC

 

[revitup]

I have experienced a FC crash every time I’ve added calcium chloride and reported it multiple times on this site. No one here understands the phenomenon so it seems to be ignored. Just be aware it happens and add liquid chlorine to bring FC back in line.

 

[JoyfulNoise]

Lots of anecdotal reports of this happening. Not a lot of science to definitely say what’s going on. It could be a heating effect from the calcium chloride granules or it could be some unknown anti-caking agent that is acting as a reducing agent towards chlorine. We had one of our experts do a test of adding calcium chloride to a test water sample and there was no discernible change in FC at all.

It’s still somewhat of a mystery as to why this happens to people and their pools and so it’s best to simply have a good amount of LC on hand to compensate of you do measure a drop in FC.

 

[kellyfair]

Why add calcium at all?

 

[reggiehammond]

Plaster pools require proper management of CSI. For vinyl pools, not necessary.

CSI and LSI - Further Reading

www.troublefreepool.com

 

[revitup]

Why add calcium at all?

Plaster pools require proper management of CSI. For vinyl pools, not necessary.

CSI and LSI - Further Reading

www.troublefreepool.com

Calcium levels are important for salt cells and heaters, even in vinyl and FG pools.

 

[Newdude]

Calcium levels are important for salt cells

*calcium will scale inside SWGs if too high and/or other parameters are favorable for scaling. Calcium itself is not a requirement of SWGs.

and heaters

The manufacturers recommended 200 CH is misguided and dates back to steam boilers. It's no longer relevant, but needs to be followed solely for warranty purposes.

 

[revitup]

*calcium will scale inside SWGs if too high and/or other parameters are favorable for scaling. Calcium itself is not a requirement of SWGs.

The manufacturers recommended 200 CH is misguided and dates back to steam boilers. It's no longer relevant, but needs to be followed solely for warranty purposes.

OK, then I’ll ask the same question as has been asked before. Why does Troublefreepool have recommended and ideal levels, including minimum levels, for CH in vinyl and FG pools?

 

[Newdude]

Why does Troublefreepool have recommended and ideal levels, including minimum levels, for CH in vinyl and FG pools?

The vinyl side has been fixed. The fiberglass side is in need of fixing.

Vinyl :



Fiberglass:


Although, if the fiberglass side is fixed, then it needs an asterisk if there are waterline tiles with grout to follow the plaster values instead.

 

[revitup]

The vinyl side has been fixed. The fiberglass side is in need of fixing.

Vinyl :
View attachment 520283


Fiberglass:
View attachment 520284

Although, if the fiberglass side is fixed, then it needs an asterisk if there are waterline tiles with grout to follow the plaster values instead.

If CH levels are not a consideration in vinyl pools, why is it still considered in the CSI calculation?

 

[kellyfair]

If CH levels are not a consideration in vinyl pools, why is it still considered in the CSI calculation?

I never paid attention to it - until I discovered scaling all over my pool, probably due to high PH while health issues sidelined me from regular pool care. Now I do look at it, trying to keep it slightly negative in the hope that the scale will slowly dissolve.

 

[Newdude]

If CH levels are not a consideration in vinyl pools, why is it still considered in the CSI calculation?

Because it's needed to calculate CSI, in the rare instance there is scaling. Most places with high CH fill water don't have many vinyl pools because they don't hold up well to the insane UV in those places.

TFP has all of its general reccomendations and also allows for some variance when the situation warrants it. It's similar to how we reccomend that folks in the hot climates use a higher CYA to compensate. It's acceptable for the few while the many fall into the general CYA reccomendations. Thousands and thousands of real world members have shaped our thoughts about both.

 

[JJ_Tex]

I have seen several members post similar stories when adding calcium. While calcium should not impact your FC, quality control from many manufacturers isn't the best either and we have seen contaminants in salt and other products.

What was the brand of calcium that you added? Did you notice anything off on the product including discoloration in the white granules?

 

[SoDel]

I ascribe to the “some contaminant in the calcium” theory because I’ve seen the FC result decrease after adding calcium in my own pool. What I’m really curious about is does this mystery contaminant actually affect the FC or does it just affect the test result in some unknown way? I’ve seen many anecdotes of significant FC test result reduction after adding calcium but have yet to see any consequence so it makes me wonder a bit: is it really reduced or does it just appear to have been reduced? Just another of the imponderables lol.

 

[revitup]

I have seen several members post similar stories when adding calcium. While calcium should not impact your FC, quality control from many manufacturers isn't the best either and we have seen contaminants in salt and other products.

What was the brand of calcium that you added? Did you notice anything off on the product including discoloration in the white granules?

I’ve never noticed anything ‘off’ with the product.

 

[cledee]

@Jimrahbe I don't understand it either. I believe others were thinking contamination possibly. I found other examples here, here, and here, for example

I went back and re-read those 3 post and they all had something very similar in which their FC were at or close to the minimum for their CYA.

 

[revitup]

I went back and re-read those 3 post and they all had something very similar in which their FC were at or close to the minimum for their CYA.

Maybe, but not in my case. I always maintain in the FC 6-9+ range for CYA 70-80.