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

[duraleigh]

This thread is troubling me a little. for over 20 years, this forum (and others) have NEVER reported this FC loss when adding CH. Now one member reports a halt in FC production on his SWG and another reports a 4.0 ppm loss overnight of FC,

I don't think TFP should suggest any action to counteract this at this point. TFP knowledge thrives on science as well as anecdotal reports from pool owners. Until we can find some repeatable experiments and a scientific reason for it, we should continue our present suggestions for the addition of CH.

I strongly believe TFP needs to stay simple and adding some caveat to CH additions just doesn't have merit.........yet.

 

[mgtfp]

There actually have been repeated reports about this issue over the years (this thread for instance started in 2016). And the recommendation to check FC after adding calcium chloride has already made it into the TFP wiki article Calcium Hardness.

There are a number of threads on the topic:

Google search results

www.troublefreepool.com

I think the advice to check FC makes sense. It will also encourage others to post their experience which will help to build up anecdotal evidence which may help understanding the root cause (if there is one...).

 

[duraleigh]

There actually have been repeated reports about this issue over the years (this thread for instance started in 2016). And the recommendation to check FC after adding calcium chloride has already made it into the TFP wiki article Calcium Hardness.

This particular thread reported a FC loss of 2.4 somewhere around a 24 hour period.......with no measurement for CYA.......I would hardly call that an FC loss due to CH. "Making it" into a Wiki article only means just that. It made it into an article.

Look, I am ALL IN for understanding how pool chemistry works and making suggestions for pool care when the issue has merit. The majority of TFP members don't really care about this unproven supposition and simply want to go swimming. Those members are wa-a-ay over 97% of the members on this forum.

Arguing for the sake of the argument has no interest for me so I will re-state again that adding CH to a pool has not been an important consideration in pool water management.

 

[MichaelT20]

This particular thread reported a FC loss of 2.4 somewhere around a 24 hour period.......with no measurement for CYA.......I would hardly call that an FC loss due to CH. "Making it" into a Wiki article only means just that. It made it into an article.

Look, I am ALL IN for understanding how pool chemistry works and making suggestions for pool care when the issue has merit. The majority of TFP members don't really care about this unproven supposition and simply want to go swimming. Those members are wa-a-ay over 97% of the members on this forum.

Arguing for the sake of the argument has no interest for me so I will re-state again that adding CH to a pool has not been an important consideration in pool water management.

Just reporting in -- my CH was a bit on the low side so I decided to do a test tonight. I've been monitoring my FC and PH twice a day (Morning and night) for the past 2 weeks - its ALWAYS around 5-6 FC. I have a SWG gen and consider myself 'pretty well dialed in' on it.. I run 8am->10pm at 70% (I am gonna raise CYA a bit soon so i can turn it down).

(My pool math app should be accessible, so feel free to check my test results, including the test I just did a few minutes ago). To clarify I'm using the Taylor 2006 drip test (DPD powder) for FC testing.

Tonight I tested FC at 7:45pm. It was at 5.0 (10ml sample - 10 drops). CC was at 0.
I added 8lbs of Leslie's Hardness Plus
I just tested again, 9:15pm -- 30 minutes later -- FC is at 2.5 (10ml sample - 5 drops). CC is at 0.5 (or less, since i used the 10ml sample size).
I'll test again in another 90 minutes.

I plan to leave my pump running all night (along with the SWG) to 'replenish' my FC. I might even toss a 1lb bag of Dichlor in there (I need the CYA anyway).

Just adding this experiment to the conversation here.

Edit: An hour later and results are the same. 2.5fc and 0.5cc. Added a bag (1lb) of DiChlor which according to pool math with raise my fc around 3.1. Turned off my swg and will let it circulate all night. Gonna see how it looks in the morning.

 

[duraleigh]

A VERY accurate report, MichaelT20. Thanks. Staying in this thread. let's see if we get other reports where the FC drop is pretty well documented. Equally, let's see if we can get reports where the CH addition made no difference in the FC.

Unexplained occurrences or intermittent occurrences are troublesome. Let's see if we can make progress on exploring this further.

I will speak with Taylor today but have found their thinking to be somewhat rigid. I'll report.

 

[PoolStored]

let's see if we get other reports where the FC drop is pretty well documented.

Unexplained occurrences or intermittent occurrences are troublesome. Let's see if we can make progress on exploring this further.

I think it would be important to get the brand of Calcium Chloride that was added.

I chose not to use big box Calcium Chloride. I used DowFlake Calcium Chloride and had no associated FC drop.

 

[MichaelT20]

Thanks . Happy to help! FYI as of 8am my fc was at 5.0 and cc at 0.0. This aligns close to the +3 the bag of DiChlor should have caused (should have been 5.5).

Sunrise was at 6am so I figure a little burned off in the 2 hours between then and my testing. Swg was off all night but it’s back on starting now to maintain around 5ish.

 

[MichaelT20]

I think it would be important to get the brand of Calcium Chloride that was added.

I chose not to use big box Calcium Chloride. I used DowFlake Calcium Chloride and had no associated FC drop.

Leslie’s hardness plus. It’s definitely possible it’s brand or batch specific - this is my first pool (2 months old) and I baught all the calcium plus at the same time. I’ll need some more soon anyway so I’ll test again when I add it

 

[Toxophilite]

I dumped 8lbs of the Leslie's hardner plus this weekend and took my CH up 40 points. I didn't get any noticeable FC change though I'm not on the SWG data set.

 

[mgtfp]

. I’ll need some more soon anyway so I’ll test again when I add it

Right now your pool wouldn't mind a bit more calcium, but make sure you don't regret it in the future. You said your pool is two months old, and in your first PoolMath log from two months ago your CH was 240 - is that how it was after filling the pool before adding any calcium chloride? Is that indicative of the CH of your fill water? In this case your CH will probably keep rising anyway with fill water replacing evaporated water and you might want to keep some buffer for the future.

Or are you filling with low CH water?

Loving your good documentation

 

[MichaelT20]

Right now your pool wouldn't mind a bit more calcium, but make sure you don't regret it in the future. You said your pool is two months old, and in your first PoolMath log from two months ago your CH was 240 - is that how it was after filling the pool before adding any calcium chloride? Is that indicative of the CH of your fill water? In this case your CH will probably keep rising anyway with fill water replacing evaporated water and you might want to keep some buffer for the future.

Or are you filling with low CH water?

Loving your good documentation

The pool was originally filled by water truck, as I've been re-filling by hose I haven't noticed a CH rise, but maybe even a little decrease. Theres a LOT of kids in my pool reguarly so splash-out is a real thing haha

I should test my fill water, because I know its a little hard (based on the shower) .

Good point for sure! I'm just trying to dial it into the recommended zone, i'm still a bit shy of that 350 goal (310ish this morning).

 

[duraleigh]

I think it would be important to get the brand of Calcium Chloride that was added.

Exactly. If there is a brand (or batch) that somehow introduces impurities that will oxidize, that will add helpful info to our data.

 

[Lake Placid]

I have experienced FC loss 3 times when adjusting hardness. Each time I was adding more than 10 pounds in the adjustment, and once was over 15 pounds. With the 10 pound additions FC initially measured 5.5 - 6 and dropped to 2 - 2.5. On the 15 pound addition FC dropped sub 2 but I can’t recall how low.

I test now when adding CH and if/when I see FC dropping, I‘ll bump my cell up to 75% production from the normal 19% production level to offset the loss.

This has happened with Leslies branded CH and Regal branded CH. The 10# additions were Regal and the 15# was leslies.

 

[PoolStored]

Some big differences in SDSs

Leslie's SDS

CALCIUM PLUS (Seems to be an old product no longer sold.


Regal Pool Care System Calcium Increaser SDS (Current product)


DowFlake SDS

 

[SoDel]

If I may suggest (humbly) a “strawman” of an analytical framework,

First, do no harm. Despite there being no reason for CaCl2 to cause any effect on FC, there have been reports that it indeed occurs (and I’ve observed it in my own pool).

It doesn’t seem to hurt anything to keep an eye on FC after adding CaCl2. Up to the pool owner, but it won’t hurt to do some testing, likely either way (do or not do — it’s a choice).

We “know” it can’t be the CaCl2 itself. So if it is happening, it has to be some impurity in the product.

We can speculate on the possibilities, but without lab analysis, hard to say what we’re looking for. Depending on the end state we want, the actual cause may not matter. (like, it might happen so just be aware of it).

It would be great if we could correlate the issue to certain brands, but it’s also possible that what we get is ”run of the mill” of wherever the entity that packages it gets it. It may be equally fruitful to correlate brands and localities that, for sure, do not have the effect.

I’m not sure if this strawman framework is any change from present guidance in terms of being aware it has been reported to happen so be on the lookout in case it does.

I would really like to know the cause, but if I had to make a bet, my bet is the sources and processes used for the product are too varied to pin down a cause or supplier. I hope I’m wrong and would be happy to be wrong.

 

[Bperry]

If I may suggest (humbly) a “strawman” of an analytical framework,

First, do no harm. Despite there being no reason for CaCl2 to cause any effect on FC, there have been reports that it indeed occurs (and I’ve observed it in my own pool).

It doesn’t seem to hurt anything to keep an eye on FC after adding CaCl2. Up to the pool owner, but it won’t hurt to do some testing, likely either way (do or not do — it’s a choice).

We “know” it can’t be the CaCl2 itself. So if it is happening, it has to be some impurity in the product.

We can speculate on the possibilities, but without lab analysis, hard to say what we’re looking for. Depending on the end state we want, the actual cause may not matter. (like, it might happen so just be aware of it).

It would be great if we could correlate the issue to certain brands, but it’s also possible that what we get is ”run of the mill” of wherever the entity that packages it gets it. It may be equally fruitful to correlate brands and localities that, for sure, do not have the effect.

I’m not sure if this strawman framework is any change from present guidance in terms of being aware it has been reported to happen so be on the lookout in case it does.

I would really like to know the cause, but if I had to make a bet, my bet is the sources and processes used for the product are too varied to pin down a cause or supplier. I hope I’m wrong and would be happy to be wrong.

Why not conduct an experiment? Fill up two buckets with pool water which will have identical chlorine level. Then add a reasonable amount of calcium to one bucket and not the other. Then test the FC level in both buckets every 15 minutes or so.

 

[mgtfp]

Why not conduct an experiment? Fill up two buckets with pool water which will have identical chlorine level. Then add a reasonable amount of calcium to one bucket and not the other. Then test the FC level in both buckets every 15 minutes or so.

I like the idea. We should agree on an amount of CaCl2 per water bucket to make it comparable.

The 8lbs that Michael added would be equivalent to less than 0.5g per 10L of water - you need a good scale for that.

Maybe something like 5 or 10g per 10L (sorry, I can't think in oz and gallons)? That should be doable with kitchen equipment.

 

[Lake Placid]

I like the idea. We should agree on an amount of CaCl2 per water bucket to make it comparable.

The 8lbs that Michael added would be equivalent to less than 0.5g per 10L of water - you need a good scale for that.

Maybe something like 5 or 10g per 10L (sorry, I can't think in oz and gallons)? That should be doable with kitchen equipment.

I like the idea but should we target a more realistic estimated rise in ppm? 5g in 10L would generate an expected increase of 595 ppm. I know I was targeting about 100 ppm increase when I noted my loss. That would equate to .85g in 10L. (Someone check my math).

 

[Bperry]

I like the idea but should we target a more realistic estimated rise in ppm? 5g in 10L would generate an expected increase of 595 ppm. I know I was targeting about 100 ppm increase when I noted my loss. That would equate to .85g in 10L. (Someone check my math).

A 5 gallon bucket is maybe closer to 20L? Maybe round down a bit to leave room for the calcium and leaves a bit more buffer to measure it.

 

[Lake Placid]

A 5 gallon bucket is maybe closer to 20L? Maybe round down a bit to leave room for the calcium and leaves a bit more buffer to measure it.

5 gal is just under 19L. Thinking 4 gals is nearly 15 L and leaves 1 gallon available in a 5 gal bucket . 100 ppm rise in 4 gal is .06 oz or 1.7g.