Would it be a good idea to add a bit of calcium hardness increaser?

three4rd

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Jul 20, 2014
206
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Berks County, PA
#1
Hi,

I have been monitoring my pool chemistry ever since closing being that I had the pool replastered over the summer. And so I'm trying to keep a check on the SI so as to avoid either etching or scaling of the new plaster. Right now my numbers are:

pH - 8
TA - 80
CH - 190

The SI has been hovering around the -0.2 to -0.3 so everything should be ok, but I'm wondering if wouldn't be a bad idea to bring that CH up a bit, since it was at 210 a few months ago. Also, the TA was recently at 70 and so I brought that up to 80.

I know that the CH increaser generates some heat - I was planning on adding a bit to a large bucket of water first prior to adding the mix to the pool. I have been agitating the pool water (never envisioned using a kayak paddle for this purpose but it works great) following any additions of dry acid or TA increaser. So would it be ok to dilute some CH increaser in the bucket?

Thanks,
Keith
 

zethacat

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Sep 23, 2013
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Dallas-Ft. Worth Metroplex, TX
#2
You know what they say? If it ain't broke, don't fix it. A CSI of .3 is perfectly safe. But if you insist on being a perfectionist, it is definitely a good idea to dissolve calcium chloride in a bucket of water prior to adding it to the pool. And just to be safe, give the pool a good brushing after.
 

three4rd

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Jul 20, 2014
206
0
Berks County, PA
#3
Hi zethacat,

I don't need to be the perfectionist here. As long as I'm in a safe SI range, I'm good with that. There would not be any brushing taking place, as I only release enough springs to take back the cover part way to expose the deep end. So if there is a potential problem with not brushing following the calcium chloride addition, then I suppose the whole idea is sooner left alone. Thanks.
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
#4
The CH may continue to go down with water dilution from rains so adding more calcium would be reasonable. I do that over the winter since I'm diluting to reduce salt, but don't want the CH to get too low. CH increaser in a bucket is fine though there is a limit to its solubility so depending on how much you add you may need to use more than one bucket dump for it.

At colder temperatures and higher pH the risk for etching is reduced even with a negative CSI, but since you're going to need the CH higher for next spring anyway you can add it now if you like.
 

eqbob

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Jul 26, 2012
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Central Texas
#5
Why would one be worried about heat being generated when adding calcium? Is it exothermic enough to even raise the temp any significant degree with a few pounds in several thousand gallons of water? Also, why the brushing? If it dissolves in the water and you can see that it does, it can't be sticking to anything?

Not trying to be sarcastic...genuinely don't understand that advice....
 

gtemkin

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Jun 7, 2008
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Seattle, WA
#6
The concern about endothermic is when bucket dissolving the Calcium Chloride. It is pretty strongly endothermic. The brushing concern would be because invariably there will be un-dissolved Calcium Chloride in the bottom of the bucket which will end up being dumped into the pool and will then be sitting on the bottom of the pool unless it's brushed away.
 

three4rd

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Jul 20, 2014
206
0
Berks County, PA
#7
Chem Geek - thanks for the advice. So now, from what was mentioned in the other replies I suppose the next concern would be - what harm would any undissolved calcium chloride do on the bottom of the pool? I will likely only try a very small amount in the bucket and keep stirring until I'm sure most is dissolved.
 

JamesW

TFP Expert
Mar 3, 2011
12,647
1
#8
I would suggest a maximum of 3 lbs of calcium chloride per gallon of water. As long as you don't exceed that ratio, you should be able to get all of the calcium chloride to dissolve without overheating the water in the bucket.

Undissolved calcium chloride can stick to the bottom of the pool and should be avoided. It's probably not urgent that you add calcium now. If you want to, I would recommend pulling the cover back far enough to allow you to brush it in properly. The cover should be fairly easy to remove and reinstall if it was installed properly.
 

chem geek

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#10
The concern about endothermic is when bucket dissolving the Calcium Chloride. It is pretty strongly endothermic. The brushing concern would be because invariably there will be un-dissolved Calcium Chloride in the bottom of the bucket which will end up being dumped into the pool and will then be sitting on the bottom of the pool unless it's brushed away.
Just to avoid confusion, it's exothermic, not endothermic. An exothermic reaction releases heat so raises the temperature while an endothermic reaction absorbs heat so lowers the temperature.

The purpose of dissolving in a bucket has nothing to do with the heat of reaction, but rather with not having a bunch of calcium chloride undissolved at the bottom of the pool. High calcium levels can lead to calcium carbonate scaling in the area or form calcium carbonate covered pieces that take much longer to dissolve. Nevertheless, in my own pool when it is warm I've added calcium chloride directly and then just brushed any that didn't dissolve into the floor drain where it got caught in the filter (there was very little that didn't dissolve).
 

JamesW

TFP Expert
Mar 3, 2011
12,647
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#11
Adding the calcium chloride directly is usually fine as long as the calcium is quickly and thoroughly brushed as soon as it hits the floor. This works better in warm water than cold.

I don't know why, but when the water is cold, the calcium chloride will almost immediately stick to the bottom in a hard pile that is difficult to remove. Calcium chloride is less soluble in cold water than hot, but I don't think that it's enough to explain the difference.

Also, when adding chemicals (such as salt or calcium chloride) that will get sucked into the main drain, it's important to turn the SWG off for a while to avoid scaling the cell or over-amping the power unit.
 

eqbob

Well-known member
Jul 26, 2012
436
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Central Texas
#12
Good points and thanks for the information. When I've added calcium chloride, I weigh it out in a scoop at a time, on a kitchen food scale, stand at the end with the jets, with the jets on, and broadcast the scoop across the length of the pool. Works out to about 2 pounds per scoop. I then go get another one and do the same thing. By the time I'm back on that 100 foot round trip, there's nothing left undissolved in the water, no matter what the temperature of the water is. 6 HP is great for water agitation.
 

eqbob

Well-known member
Jul 26, 2012
436
0
Central Texas
#15
i'm the owner of that pool. I edited the second to last post of that topic to include an update. Check there for the update.
Kewl. Glad everything worked out for you. It was an interesting thread to read as we had some areas we thought were stains and were stressing them as well. Diagnosed as micro-fractures and calcium leaching from behind the plaster. Didn't want to go the cut out and try to match route....was told it would never ever match. Wound up just chipping off the calcium. It sealed the micro-fracture and all's well. Lot's of angst on the plaster and pool maintainer's part and finger pointing at it's their fault. I could relate to your frustrations as I read your thread. Thanks for responding with the update. Glad it's good to go for you!
 

three4rd

Well-known member
Jul 20, 2014
206
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Berks County, PA
#16
Thanks for all the helpful replies. My CH level is now around 160-170. This is the test that I find hardest to do since there seems to be no clearly discernible change from the pinkish to bluish color with my Taylor test kit. Compared to doing a TA test, I find the CH much more difficult to actually determine the level, but I'm pretty sure that 160-170 is about where I'm at - down from 210 back in November.

Right now my SI is -0.21. (TA is at 70 and pH right around 8) I played around with the CH numbers a bit and find that you have to either raise or lower the level significantly to yield a substantial change in the SI. For instance, if I plug in a CH reading of 200 I get an SI of -0.14. If I go as low as 130, the SI is then -0.32. Actually, I can take the CH all the way up to 600 and the SI is still only at 0.34. I find this hard to believe. I would have thought changing the CH numbers between that wide a range would result in a more drastic change to the SI, so based on where I'm at right now, at -0.21, I would say nothing needs to be adjusted. Is my thinking correct?

Thanks,
Keith
 

three4rd

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Jul 20, 2014
206
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Berks County, PA
#17
Would it be a good idea to bring up the TA just a bit?

As a follow-up to my other thread about adding the CH increaser, what I am wondering now is this - is the CH is going to continue on a downward trend from rain / snow dilution which seems to be what has been happening (went from 210 in November down to 160-170), I notice on the SI calculator that if I bring the TA up from the current 70 to around 90, then in the event that the CH level drops further I still stay in a safe range. My main goal is to avoid etching of the new plaster. It does appear that the pH is no longer continuing to go up as it did after the replaster back in July. It is staying at 8 but of course rain and snow probably have had an effect on keeping it in check. Right now the SI is -0.23, but if the CH drops to 120 and the TA remains around 70 or lower, then the SI will begin to go below -0.3. Any thoughts? Leave everything where it is? I'd rather adjust the TA then fool around with CH increaser due to the concerns raised about the possibility of some not dissolving even though I would pre-dissolve in a bucket first. I know the TA increaser dissolves easily in the bucket. I'm probably over-thinking all of this and too worried about the plaster (?)

Thanks,
Keith
 

duraleigh

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#18
Re: Would it be a good idea to bring up the TA just a bit?

Almost every pool will slowly increase in CH. I believe yours will too.

That said, it is a bit too low and I would consider increasing it to 250. Why would you not?

pH should not remain above 7.8 for any long period of time. Why do you think 8+ is OK?

I would ignore your TA for now. You seem to be disregarding CH and pH for far less important TA and way, way far less important CSI

Have you read this article in Pool School?

http://www.troublefreepool.com/content/134-recommended-levels

By the way, it is VERY helpful to keep your posts in one thread....frequent responders will not see you seperate threads and you will be skipped.
 

three4rd

Well-known member
Jul 20, 2014
206
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Berks County, PA
#19
Re: Would it be a good idea to bring up the TA just a bit?

Hi Duraleigh,

I'm confused. You refer to CSI as being rather unimportant. I thought just the opposite - that as long as your SI is in a range that is neither scaling nor etching, you're fine. Is this not the case? Even though if one particular aspect of the overall chemical equation is out of recommended range, I was told that as long as the overall picture, as presented by one's SI number, is ok, then you're alright. This is not to say that one should ignore recommended ranges, and I certainly don't mean to do that. If I drop the pH much below 8, though, then it does throw the SI significantly into the etching range. I am operating under the assumption that the various individual parameters, even if out of recommended ranges, can combine within the SI formula to produce "balanced water". Also, I was told here that having the CH a bit low going into the first winter with new plaster is a good idea.
 

JasonLion

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May 7, 2007
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#20
It is true that CH only has a small effect on the saturation index. PH is by far the most significant, while TA is somewhere in-between PH and CH.

We don't recommend leaving CH as low as that. On the other hand, from what you said it sounds like adjusting it doesn't need to be an especially high priority at the moment.

On the other hand, I am a little worried about the drop in CH of 40-50 in the last few weeks. That is either a testing problem or indicates a substantial loss of calcium to somewhere, possibly a leak? Do you know of any reason CH should have gone down (backwashing, leak, etc)?