Can adding a lot of calcium chloride at once reduce FC??

[RickRude]

I am experiencing this FC drop phenomenon.

18 November, 8:40 pm: FC @ 3 ppm
19 November, 12:55 pm: Added 15 lbs of calcium chloride, and 4 lb of dry stabilizer
20 November, 8:51 pm: FC at zero. Added 69 oz of 12% LC (it's all I had left...should bring me to 3.1 ppm)
21 November, 7:00 pm: FC back at zero. CYA is 30 ppm.

Pool gets nearly no direct sunlight this time of year.

Calcium product is "Pool Mate" brand from Amazon. In an older thread I posted its SDS

Calcium Chloride COMPOUND and prices

We have had maybe 2” of rain, yes 2 inches, in the last year in my area of Las Vegas.

www.troublefreepool.com

 

[Bperry]

I am experiencing this FC drop phenomenon.

18 November, 8:40 pm: FC @ 3 ppm
19 November, 12:55 pm: Added 15 lbs of calcium chloride, and 4 lb of dry stabilizer
20 November, 8:51 pm: FC at zero. Added 69 oz of 12% LC (it's all I had left...should bring me to 3.1 ppm)
21 November, 7:00 pm: FC back at zero. CYA is 30 ppm.

Pool gets nearly no direct sunlight this time of year.

Calcium product is "Pool Mate" brand from Amazon. In an older thread I posted its SDS

Calcium Chloride COMPOUND and prices

We have had maybe 2” of rain, yes 2 inches, in the last year in my area of Las Vegas.

www.troublefreepool.com

I dunno if that says much that you lost 1.5ppm per day. That’s within the normal FC loss per day. If you didn’t check that the 69oz reached its target then hard to say anything conclusive.

But get your FC up around 5ppm and do an OCLT to see if it’s algae.

 

[RickRude]

I dunno if that says much that you lost 1.5ppm per day. That’s within the normal FC loss per day. If you didn’t check that the 69oz reached its target then hard to say anything conclusive.

Fair enough. I might have added LC on the evening of the 19th as well, but cannot confirm since I didn't log it. I do not log every FC test and add this time of year bc loss rate is slow and adds are small. What I can tell you, with certainty, is that this rate of chlorine loss is nearly unprecedented in my pool. The only other time I recall experiencing something like this was when I added a bottle of polyquat.

 

[ajw22]

Fair enough. I might have added LC on the evening of the 19th as well, but cannot confirm since I didn't log it. I do not log every FC test and add this time of year bc loss rate is slow and adds are small. What I can tell you, with certainty, is that this rate of chlorine loss is nearly unprecedented in my pool. The only other time I recall experiencing something like this was when I added a bottle of polyquat.

We have seen this before and do not have a chemistry explanation for what is occurring.

We advise keeping a close eye on the FC level after adding calcium then adding as much liquid chlorine as necessary to get the FC up and hold the level.

 

[JoyfulNoise]

We have seen this before and do not have a chemistry explanation for what is occurring.

We advise keeping a close eye on the FC level after adding calcium then adding as much liquid chlorine as necessary to get the FC up and hold the level.

My “chemistry explanation” of this is that the product being bought is not as pure as the SDS indicates and that there is some kind of contaminant in the solid material that causes a rapid reduction of chlorine. It could be an intentionally added anti-caking agent, some of which are know be reducing agents, or it could just an organic contaminant in the material. Since calcium increaser is added in very large doses (pounds of material added all at once), even a small amount of contaminant could cause measurable changes in FC levels.

Bulk solid chemicals can be sourced from a lot of different suppliers and it is almost a given that stuff coming from overseas will have questionable purity. This is why chemists always standardize mixtures in a lab and will often use purification techniques to achieve higher quality and purity of chemical reagents.

As for pool owners, you just have to go with what you got and hope it mostly works.

 

[Bperry]

Fair enough. I might have added LC on the evening of the 19th as well, but cannot confirm since I didn't log it. I do not log every FC test and add this time of year bc loss rate is slow and adds are small. What I can tell you, with certainty, is that this rate of chlorine loss is nearly unprecedented in my pool. The only other time I recall experiencing something like this was when I added a bottle of polyquat.

Not saying you’re wrong, just that it’s not so easy to confirm. I added more than 50lbs and didnt notice much FC loss.

 

[7rdr7]

Not saying you’re wrong, just that it’s not so easy to confirm. I added more than 50lbs and didnt notice much FC loss.

I just experienced the same issue. FC was 3.5, added 8lbs of Calcium Chloride, FC now 0.5. This is in a 33k pool.

 

[JoyfulNoise]

My guess on this is that there are probably brands of calcium increaser that use ferrocyanide salts (calcium- , sodium- , or potassium ferrocyanide) as a flow and anticaking agent. Ferrocyanides undergo reversible redox (reduction/oxidation reaction) -

[Fe(CN)6]4− ⇌ [Fe(CN)6]3− + e−
ferrocyanide ⇌ ferricyanide plus an electron

That electron can be taken up by the chlorine ion (Cl+) in hypochlorous acid and converted to chloride (Cl-). Because of the reversible nature of redox reaction, even trace amounts of ferrocyanide could deplete higher levels of chlorine. The ferrocyanide will break down quickly so it’s not a permanent issue and the amount of iron exposure is insignificant.

 

[mgtfp]

My guess on this is that there are probably brands of calcium increaser that use ferrocyanide salts (calcium- , sodium- , or potassium ferrocyanide) as a flow and anticaking agent. Ferrocyanides undergo reversible redox (reduction/oxidation reaction) -

Interesting guess, I like that.

A while ago we had a discussion where we observed Calcium Chloride going brown when pre-dissolving in a bucket:

HY-CLOR Calcium Chloride impurities

I bought HY-CLOR brand Calcium Increaser from bunnings, put 2.5K in a bocket of water, left it 5 days, found that all the white pellets desolved wth dark brown sedements at the bottom of the bocket. Last time I put some in the skimmer basket in a cloth, I found the same color on part of the...

www.troublefreepool.com

It seems to have been a particular batch of that Aussie brand. Usually the calcium chloride of that brand comes in round pellets, but this one was flakes. And only that batch showed this effect. I contacted the manufacturer at the time who asked me to send in a sample which I did. But despite following up multiple times, they never got back to me and decided to sit that one out.

At the time, I had never heard of FC disappearing when adding calcium chloride, and didn't run specific FC tests. I used that brand (not the brown-turning batch) when I ran a trial on this FC disappearing phenomenon without a significant effect (see post 73 in this thread).

Wondering now if that brown colour was caused by ferrocyanide salts. I did keep a sample of that batch for a while, but eventually got rid of it.

 

[JoyfulNoise]

Calcium chloride is a deliquescent salt. In its pure form, the calcium chloride mass will absorb water into its crystal structure rather than the ions becoming solvated by water molecules. This causes the salt to look wet and feel slimy in macroscopic quantities. This can very easily lead to salt bridging.

So when manufacturers package calcium chloride for applications like pool chems or road salt, they have to add anticaking agents or else the package will turn into a giant salt-block brick.

 

[JoyfulNoise]

Perhaps one way to test this would be to take a sample of CH increaser, dissolve a small amount in water and then add a few drops of diluted ferric chloride. Ferric chloride will react with trace amounts of ferrocyanide to form the mixed valence compound iron(III) ferrocyanide, aka Prussian Blue. The Prussian Blue forms insoluble blue crystals in water that will give the water a deep blue tint.

Might be an interesting test …

 

[Newdude]

Calcium chloride is a deliquescent salt. In its pure form, the calcium chloride mass will absorb water into its crystal structure rather than the ions becoming solvated by water molecules

Funny you mention this. The damp-rid I bought for my moving pods was calcium chloride.

 

[mgtfp]

Perhaps one way to test this would be to take a sample of CH increaser, dissolve a small amount in water and then add a few drops of diluted ferric chloride. Ferric chloride will react with trace amounts of ferrocyanide to form the mixed valence compound iron(III) ferrocyanide, aka Prussian Blue. The Prussian Blue forms insoluble blue crystals in water that will give the water a deep blue tint.

Might be an interesting test …

So we need to find the electronics geeks who etch their own PCBs...

 

[JoyfulNoise]

So we need to find the electronics geeks who etch their own PCBs...

Hahaha. I preferred cupric chloride with a little bit of added HCl when I would etch boards … it’s a more pleasant color than ferric chloride which looks like the urine sample from a dehydrated meth addict …

Those etchants are too concentrated. All you need is a few mmols of ferric chloride (with a little KCl and perhaps a splash of peroxide) to make the color pop …

 

[duraleigh]

I got an "etchant" once. A prolonged course of antibiotics finally took care of it.

 

[pooldewd]

Just wondered— did anyone ever get to the bottom of this?

New plaster pool, have been maintaining with liquid chlorine since mid April until they turn on the salt generator in 11 days.

I’ve been maintaining levels at:

FC- 4.5
CC- 0
ph- 7.6-7.8
TA- 80
CYA- 70
CH- 170
Tem- 80F-85F

Added 58 pounds of calcium chloride from Amazon (Pool Mate) over the morning to bring up CH to 350.

Noticed strong pool chlorine odor when swimming, shortly after. First time I ever noticed kids eyes irritated from our pool water.

When testing at the end of the day, dropped from FC 4.5 in the AM to .5 in the evening:

FC- .5
CC- 0
ph- 7.6
TA- 80
CYA- 70
CH- 350
Tem- 83F


Typically would see about a 1-1.5 ppm drop in FC each day. Since I’m new, I’ve been doing ph and FC testing morning and night until I get the hang of it… never had had a drop this dramatic.

 

[Newdude]

did anyone ever get to the bottom of this?

Yes. We can't replicate it at will, but it's reported enough that we believe it, so blame goes to the manufacturer with impurities at times.

 

[mgtfp]

Just wondered— did anyone ever get to the bottom of this?

New plaster pool, have been maintaining with liquid chlorine since mid April until they turn on the salt generator in 11 days.

I’ve been maintaining levels at:

FC- 4.5
CC- 0
ph- 7.6-7.8
TA- 80
CYA- 70
CH- 170
Tem- 80F-85F

Added 58 pounds of calcium chloride from Amazon (Pool Mate) over the morning to bring up CH to 350.

Noticed strong pool chlorine odor when swimming, shortly after. First time I ever noticed kids eyes irritated from our pool water.

When testing at the end of the day, dropped from FC 4.5 in the AM to .5 in the evening:

FC- .5
CC- 0
ph- 7.6
TA- 80
CYA- 70
CH- 350
Tem- 83F


Typically would see about a 1-1.5 ppm drop in FC each day. Since I’m new, I’ve been doing ph and FC testing morning and night until I get the hang of it… never had had a drop this dramatic.

Best theory we have so far is in post #88 in this thread.

 

[mgtfp]

Noticed strong pool chlorine odor when swimming, shortly after. First time I ever noticed kids eyes irritated from our pool water.

And thanks for adding this detail, that's interesting.

 

[Lake Placid]

Noticed strong pool chlorine odor when swimming, shortly after.

And thanks for adding this detail, that's interesting.

I would think that CC would have tested higher from the earlier test given the strong chlorine smell. One would assume chloramines, no? @pooldewd did you smell the chlorine smell during the second test?