Chlorine Scaling?

[agogley]

I have a 20K gallon negative edge pool. I can't seem to control what appears to me to be calcium deposits on the pool plaster. To me they look a lot like efflorescence. The pool is a SWG with ozonator. It is blue-black colored plaster (looks blue). The white calcium can be sanded off, although the plaster seems to become white and discolored with the calcium deposits (so in many spots it looks like the calcium deposit is there even though the plaster is smooth to the touch).

First of all, I've had a horrible frustration with pool store results. I've had instances where I've taken pool water to three different pool stores within a few minutes and gotten completely different results. So now I have two home test kits. One is a Blue Devil kit and one is the TF-100 kit recommended here. I did multiple tests with both home kits and there is no way the calcium is less than 190.

Pool Store Results: 4.0 CL, 7.6 PH, 145 CH, 100 TA, 45ppm CYA, Salt 3000, total dissolved solids 1200.
TF-100 Results: 4.0 CL, 7.8 PH, 200 CH, 90 TA, 45 CYA, Salt 3000
BD Results: 40 CL, 7.8 PH, 200-250 CH (test is by 50s), 90 TA, 45 CYA

Jandy SWG recommended ranges: 1-3 CL; 7.2 - 7.8 PH; 150-400 CH; 80-120 TA; 50-75 CYA (75-85 summertime); 3000-3500 salt.

The precipitate happens very quickly. If I sand off all the spots one week, I could have more precipitate by the following week. Sometimes my PH gets a little higher than it should, but usually I try to keep it in the 7.4 range (Jandy manual says 7.8 is a natural level for SWG).

I also have to say that I've suspected that my calcium is higher than what the stores have been telling me. Often the stores would test at less than 400 but my Blue Devil kit tested much higher (TF-100 just came this week). I should also add that I suspected hard water at the house as contributing to problem as my faucets all get a white ring around the base and the shower heads have white crust too. My pool line has a calcim ring, although it doesn't come off without an acid solution and much scrubbing (it doesn't fizz). This summer we had a lot of rain, which I believe lowered the calcium levels.

Anyways, I'd like to keep my calcium levels low as I think they could rise up. If my home test is reliable, I want to stay with that level. But whom do I trust? The store or the

 

[Darkside of the Pool]

First of all, I've had a horrible frustration with pool store results. I've had instances where I've taken pool water to three different pool stores within a few minutes and gotten completely different results. So now I have two home test kits. One is a Blue Devil kit and one is the TF-100 kit recommended here. I did multiple tests with both home kits and there is no way the calcium is less than 190.
(...)
I also have to say that I've suspected that my calcium is higher than what the stores have been telling me. Often the stores would test at less than 400 but my Blue Devil kit tested much higher (TF-100 just came this week).
(...)
Anyways, I'd like to keep my calcium levels low as I think they could rise up. If my home test is reliable, I want to stay with that level. But whom do I trust? The store or the (?)

Trust yourself. You have legit reasons not to trust the stores (at least when chemicals are concerned).

There are ways to test what the deposit is, if you can get a sample. Test it with MA, if it reacts it is calcium carbonate. Solution is to keep PH/Alcalinity lower to couterbalance, partial drain/refill, reverse osmosis (procedure I am not familiar with, where I live most pools are partially drained every year as part of closing/opening).

If it didn't react, bring FC in the sample very high. If it clears up, whatever it is, it is organic.

I believe, like you, this might be scaling, but a better diagnostic might save you a couple bucks.

Hope that helped.

 

[Bama Rambler]

Your test numbers doesn't indicate a scaling problem. The fact that it doesn't fizz when you put muriatic acid on it indicates that it's possibly not calcium. What strength acid are you using?

Post some pics of it and maybe we can help.

Oh yeah, trust your own testing. When doing the calcium test, be sure to swirl till your arm hurts if you don't have a magnetic stirrer.

 

[agogley]

Well, to clairfy the line around the pool (at the water line) doesn't fizz up. I haven't tried using MA on the line around my faucets either, but it may not be enough to fizz (I use CLR on the faucets).

I pulled a teeny tiny sample of the wall of the pool. It did fizz up when I added a drop of muriatic acid. I'll try to get a decent photo, but it will be hard because the camera seems to focus on the top of the water.

BTW, on the testing, I purchased a magnetic stirrer. I ran all of the tests probably ten times to make sure I could duplicate the results not once, but several times. On the calcium test there is a point where the color changes but doesn't turn fully blue. I recorded both the point at which the color changed and when it turned fully blue and each time the result was the same. (range 190 to 230 on the color change). I picked 200 as spot when I should pull the reading. In other words, no way should the store have read 145. (and BTW, they totally do the CYA test wrong because they don't wait the recommended time before reading the test).

Last point. I discovered that the pool stores overcharge for nearly everything. I found a website with free shipping that is far less than any of my local pool stores (except for MA and salt).

 

[Bama Rambler]

With the CH test (as with the others) you drop until the color stops changing. When you're dropping and it starts to change to blue you keep dropping till it doesn't change and then don't count the last drop. If I'm reading right yours is really 230 or higher.

 

[agogley]

I picked 200 as the low end. The 230 result was maybe shades of blue. At 190 it changed from light pink to a bluish purple color. At 200 it changed to blue and remained blue (prior to 190 the sample would change colors but as it was swirled by the magnetic device it went back to pink). At 210 to 230 it may have slightly changed blue color. But 230 would match the blue devil test which tests by increments of 50. For giggles I ran some aquastrip tests (what a waste of money those were but that was when I first suspected store problems and didn't know to buy a good test kit). Suprisingly, the aqua strips also came out with calcium at around 250.

(Did I tell you I hate the pool stores? A bunch of $10 a hour kids telling me how to manage my pool. One time I lost my composure and got snippy with them when I caught them doing the CYA test wrong).

 

[chem geek]

For giggles I ran some aquastrip tests (what a waste of money those were but that was when I first suspected store problems and didn't know to buy a good test kit). Suprisingly, the aqua strips also came out with calcium at around 250.

Check again. Test strips don't measure Calcium Hardness (CH); they measure Total Hardness (TH) which includes magnesium. The ratio of CH to TH varies by water source, but typical sources have CH be around 70% of the TH so around 175 in your case. Basically, you can't use test strips to check for CH.

 

[PaulR]

(and BTW, they totally do the CYA test wrong because they don't wait the recommended time before reading the test).

One time I lost my composure and got snippy with them when I caught them doing the CYA test wrong).

"Wrong" in what way? There are variations in the instructions that you'll find in different places. Some variations aren't worth getting snippy about.

The Extended Test Kit Directions for CYA says to shake 30 seconds, then read. This matches Taylor's description.

The Water Testing Instructions on One Page say to shake 30 seconds, wait 2-3 minutes, then read. This extra time is mainly from a recommendation by waterbear, as I recall, although I don't have the citation handy.

I would get snippy about mixing significantly less than 30 seconds, because that's what the manufacturer's instructions say to do. I would not get snippy about failing to wait the 2-3 minutes, as that's one (admittedly experienced) opinion. (waterbear has a lot of experience and holds strong opinions on certain topics, but he is not always able to articulate the reasoning behind those opinions; some people adopt his suggestions and others do not.)
--paulr
mods pls move if this is straying too far

 

[4JawChuck]

Are you sure it isn't salt?

 

[Darkside of the Pool]

(Did I tell you I hate the pool stores? A bunch of $10 a hour kids telling me how to manage my pool. One time I lost my composure and got snippy with them when I caught them doing the CYA test wrong).

Ask to see the manager.

Most of these kids are well intended, and kept a bit in blissful ignorance. That way they can be ''honest'' without actually telling the truth. It is a modus Operandi through the industry, not something done on purpose.

You accepted to be serviced by a 10$ an hour kid.