Need to add calcium

[haze_1956]

I was doing work for an ex-neighbor today. First time I had been to their house in a couple years.

Last year they had a gunite pool installed and he was complaining the plaster was geting rough and mottled looking. He had gotten the Pool Company, 20 minute tutorial and a package of test strips.

I went home and got my test kit,
Cl 3
ph 7.2
Alk 100
Cya 90
Hardness 0 !!!!

I know he needs to add calcium chloride. But not sure best source, I seem to recall "Ice Melt" was acceptable. Just want to verify or get recommendation for alternate or preferrable source.

Thanks

[dawndenise]

I'm not sure how to post links to a past post, but you can go to a post entitled, "Calcium" on this forum with a date of 7/1/06 and you'll see the whole discussion of DowFlake as a calcium increaser.

You might want to encourage your ex-neighbor to check out this forum as it appears his/her chlorine levels are not adequate for a CYA level of 90. You did your ex-neighbor a real favor testing the water for them and giving them some direction .

[waterbear]

Here is a link to the Dow Chemical website on their products for pool and spa use...Dowflake is the most easily obtained since it is used as a de-icer.
http://www.dow.com/calcium/app/poolspa.htm

[haze_1956]

Managed to find 50 pound bags of Calcium Choride Flakes for $14.00 at a masonry supply.

Thought that was reasonably priced !

[haze_1956]

Ok, I am a bit confused now, so I am in need of the wisdom of the many !

DId the following to 38000 gallon gunite pool:

7-26 Checked pool, no hardness reading, just turned sample a little yellowish
7-29 Added 50 pounds of Calcium Chloride flakes
7-31 Checked and still getting only a little yellow in sample
8-1 Added 100 more pounds of Calcium Choride flakes
8-3 Checked and got a nice reddish/purple in sample, tested out at 600 on Hardness

This was a bit high, but Cya is 90 -100 anyway, so figured drain and refilling in a couple weeks would take care of both problems

8-22 Stopped by to check pool and again reading no hardness, test turns a little yellowish not red/purple at all.

Can anyone tell me what happened ?

Did the plaster reabsorb the Calcium?
.

[waterbear]

Ok, I am a bit confused now, so I am in need of the wisdom of the many !

DId the following to 38000 gallon gunite pool:

7-26 Checked pool, no hardness reading, just turned sample a little yellowish
7-29 Added 50 pounds of Calcium Chloride flakes
7-31 Checked and still getting only a little yellow in sample
8-1 Added 100 more pounds of Calcium Choride flakes
8-3 Checked and got a nice reddish/purple in sample, tested out at 600 on Hardness

This was a bit high, but Cya is 90 -100 anyway, so figured drain and refilling in a couple weeks would take care of both problems

8-22 Stopped by to check pool and again reading no hardness, test turns a little yellowish not red/purple at all.

Can anyone tell me what happened ?

Did the plaster reabsorb the Calcium?
.

What test kit are you using....The aquachem 6 way has an issue with the calcium hardness test that has been discussed previously in the forum....sounds like the one you are using since you said you got a yellow color

[haze_1956]

Used both an aqua chem and an hth test kit, same result on both, positve and negative.

Either way, it went from no reading. to a definite reading, back to no reading. over a 3 week period.

The calcium level did increase, then decrease as far as I can figure.

Thoughts?

[waterbear]

If I am not mistaken both these kits use a 2 reagent test. the indicator and titrant. The test in Taylor kits and Ben's uses a 3 reagent test; calcium buffer, indicator, and titrant; and does not have this problem....perhaps it is time for a better test kit? When you add the indicator it should turn pink if there is hardness present or blue if there is none. A yellow color indicates some interferance to the test. As a work around you can try adding more indicator drops until you get either the pinish or bluish color. I have done this and it has not affected the results when I have cross checked with a different test kit but I really don't know if this will alway be true. It might have some effect on the results.

[haze_1956]

My question is not whether the calcium is there.

It was there 2 days after I added it, as shown by positve results on both test kits, (as per the instructions for each). Which leads me to believe the although these tests may be imprecise, they did show a Hardness presence, 600 ppm. I would conclude that if it was there then, and is still there now, the tests would again indicate it,

Now those same test procedures shows no presence. ( I added many more drops to see if color change would happen, however it didn't )

So my question is, where could the calcium have gone ?

[waterbear]

My question is not whether the calcium is there.

It was there 2 days after I added it, as shown by positve results on both test kits, (as per the instructions for each). Which leads me to believe the although these tests may be imprecise, they did show a Hardness presence, 600 ppm. I would conclude that if it was there then, and is still there now, the tests would again indicate it,

Now those same test procedures shows no presence. ( I added many more drops to see if color change would happen, however it didn't )

So my question is, where could the calcium have gone ?

Ther presence of a yellow color indicates some interference to the test...not a lack of calcium. Like I said before, there seems to be a problem with some unknown interference with these test kits. Not sure if it might be chlorine levels, pH, metal interferance, or what but these kits do not constistanly produce correct results.