Calcium and SWC's

Hi all,
Been keeping my gunite pool on the low side for calcium, as I am afraid to coat my salt water chlorinator plates with a bunch of calcium, am I in danger of pulling calcium from the pool and damaging my walls ?

Gunite pool -1995
fc = 3
ta = 120
calcium = 80
ph = 7.2
CYA =0 [if you ever read "cyanurics-benefactor or bomb" you'll stay low as well]
I use Ben's test kit for these

If I need to add calcuim , can I use some other source[Home Depot] for calcium chloride/carbonate so I dont have to pay pool store prices ?
P.S Pool has some very hard white crusty stuff on tile from previous owner- I cant get it off , assume its calcium ?

Quote:

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Originally Posted by jacthiele

Hi all,
Been keeping my gunite pool on the low side for calcium, as I am afraid to coat my salt water chlorinator plates with a bunch of calcium, am I in danger of pulling calcium from the pool and damaging my walls ?

Gunite pool -1995
fc = 3
ta = 120
calcium = 80
ph = 7.2
CYA =0 [if you ever read "cyanurics-benefactor or bomb" you'll stay low as well]
I use Ben's test kit for these

If I need to add calcuim , can I use some other source[Home Depot] for calcium chloride/carbonate so I dont have to pay pool store prices ?
P.S Pool has some very hard white crusty stuff on tile from previous owner- I cant get it off , assume its calcium ?

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WOW... yes you're doing damage to your plaster by keeping low calcium. You're too concerned with calcium scaling in your cell, but you should not be. Rather, you have to look at your water "balance" instead. This will tell you if your water quality has a tendency to form scale, be corrosive or is balanced. This is the combined effects of total alkalinity, calcium hardness, pH and water temps. Your water test shows you are very corrosive. This will lead to your plaster pitting, grout falling apart, metals dissolving and other equipment damage.
I believe there is a link to determine your water saturation index.
On another note, although there is some merrit to the "benefactor or bomb", don't hold it as gospel. Low or no cya will cause you to use more chlorine. In the case of the swc, you will be running a higher output to maintain your chlorine residual. Which will ultimately lead to shorter cell life.
If you're not comfortable with the recommended 60 - 80 ppm of the swc, run at least 30 - 50 ppm.

Quote:

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Originally Posted by jacthiele

Hi all,

Gunite pool -1995
fc = 3
ta = 120
calcium = 80
ph = 7.2
CYA =0 [if you ever read "cyanurics-benefactor or bomb" you'll stay low as well]
I have read it and Ben has posted about it on here. It mainly deals with ORP readings not being as high with CYA in the water. This is then exterpolated to imply that the sanitation effects of the chlorine are thus reduced. While this has been oberved empirically the conclusions in the above mentioned article go a bit far. Basically the writer states that ORP meters stop working at about 50 ppm CYA and that makes automatic control of chlorination in a commercial pool impossible. The artice is more about commercial pool automation. He also cites an example comparing the ORP reading of .1ppm FC with 0 ppm CYA at pH 7.2 being the same as one with 3ppm FC, 30 ppm CYA and pH of 8. Now most of the oberved difference in ORP reading in this case has to do with the fact that at 7.2 pH the ratio of hypochlorous acid vs hypochorite ions in the water is much more toward the hypochlorous acid side of the eqaution and at pH of 8 there is very little hypochloruous acid in the water vs hypochlorite ion. Hypochlorous acid is what actually is a sanitizer and is what raises the redox potential of the water! This change in pH will have a tremedous impact on the redox potential which is what the ORP meter is reading. This example is a bit misleading because it is NOT only looking at the CYA level but is including another factor that has a large impact on ORP readings. ORP meters have some merit but there are many factors that need to be taken into consideration with their use. I happen to have experience with ORP meters in salt water aquariums so I know a bit about this.

I run 60 to 80 ppm with my SWG.

I find it extremely interesting to note that the author state at the end of the article that he has used CYA sucessfully and with benifit for years in his own pool!
I use Ben's test kit for these

If I need to add calcuim , can I use some other source[Home Depot] for calcium chloride/carbonate so I dont have to pay pool store prices ?

I would bring the calcium level up to about 200 ppm or a bit higher with a TA of 120. If you don't want to pay pool store prices then look for Dowflake brand de-icer (might be hard to find during the summer). This is one of the two Calcium chloride products that Dow makes that they recommend for pool/spa use.

HERE IS THE INFO OFF OF THE DOW WEBSITE FOR POOL AND SPA APPLICATIONS:
http://www.dow.com/calcium/app/poolspa.htm


You don't want to use calcium carbonate. It had a very low solubility and will most likely cloud the pool. In fact, when a pool gets cloudy from putting in Alk increaser and calcium at the same time it is becuase calcium carbonate has precipitated out into the water!
P.S Pool has some very hard white crusty stuff on tile from previous owner- I cant get it off , assume its calcium ?

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Hope this helps

Poolsean,
Good to see you again, I bought a pool pilot last year via your and others advice, I forgot to ask you how I should clean the grid, I cant find it in the manual ?

And you said "very corrosive", what is making my water so bad, just the low calcium or something else you see as well ??

Thanks jacthiele. Corrosive due to the calcium and pH being on the low side.
For cleaning the grid, or cell blades, do you see signs of white calcium build up? With corrosive water, or lower pH levels, you usually do not see calcium on the cell blades.
However, it is located in the manual. one part muriatic acid added to 4 parts water in a container tall enough to submerge the cell blades. ALWAYS ADD ACID TO WATER AND NOT THE OTHER WAY AROUND.