Low calcium levels, plasticizers in vinyl liners, leaching cobalt from fibergalss?

[PoolDoc]

Amazingly enough, I was just about to start a new thread when I saw this one. My basic premise is this:

All pools need some calcium

Now my above conclusion is based on the the Langelier Saturation index. I suppose the real question is, do you believe in the SI or not?

For what it's worth, Dr. Langlier didn't . . . at least for pools! He was rather dismayed to see his boiler corrosion index, for use in closed systems NOT exposed to air, applied to pools. I've got a copy of a letter he wrote on the topic somewhere. If I ever run across it again, I need to scan and post it!

Here's the deal. With the SI, you want to keep your water "balanced". That is to say, not in a corrosive condition, and not in a scaling condition. I was answering some questions today on here, and ran a few scenarios through the SI calculator found here:

No calculator links here, please!

I put up my own calculator a few years ago, mainly to try to correct the false impression of precise Langlier values given by calculators like the one you linked to. The Langlier index is a composite value, calculated from a conglomeration of approximate values. As a result, it's even MORE approximate.

What I mean is, if you test and find the following values:

• pH => 7.6,
• Alk => 110,
• Cal => 180,
• Temp => 83, &
• TDS 1200; and
• a calculated Langiler of -0.1 (which is 'excellent')

then you can assume that the

• ACTUAL pH is between 7.4 & 7.8,
• your ACTUAL Alk is between 90 & 130,
• your ACTUAL Cal is between 150 and 210,
• your ACTUAL temp is between 80 & 86, and
• your ACTUAL TDS is between 500 and 2000,

assuming you used a PS233 + an uncalibrated pool store thermometer + a Hanna TDS meter. In this case,

• the ACTUAL langlier index would be between -0.3 and + 0.55, or
• somewhere between a little low and definitely too high!!

The range of possibilities gets much wider, if you use test strips, or have water carried in your car all day tested at the dealers!

The point of all this is that, unless you are going to to lab qualities tests, doing the titrations with precision burets filled with reagent grade chemicals, and using a *calibrated* pH meter and a *calibrated* digital thermometer, and a *calibrated* TDS meter . . . your pool test measurements aren't really accurate enough to generate a meaningful Langlier index or Ryznar index (the Hamilton Index is a 'seat of the pants' index).

Fortunately, it doesn't matter!

There has NEVER been any research (at least that I have been able to find) that shows that the Langlier works for pools. The ONLY research I have on that topic, done by John Wojitiowicz, who was Olin's pool chemical research chemist for years, suggests it does NOT work, and that pH and alkalinity are much more important than the other factors.

This fits very well with my experience: old pools where the pH and alkalinity were controlled have decent plaster -- regardless of whether they paid attention to calcium or not. Old pools where they had pH 'accidents' have been replastered.

Put another way: commercial pools that used bleach (which is higher in pH) may have some stains on the plaster, but it's still sound. Commercial pools that used tri-chlor (low in pH) have usually be replastered one or more times, over a 15 year period.

These facts may explain why I try to de-emphasize the Langlier and Rynar indices. The Hamilton index is really a rough, seat of the pants, index that was mainly designed by Jock Hamilton of United Chemical, so those who 'had to have' an index, had one. It favors high pH, because high pH favors the bromine chemistry that's in virtually every product United sells.

But, wait, there's another HUGE error in the way the Langlier index is applied to pools! The one place where the Langlier is most likely to be meaningful, is inside the heat exchanger of a pool heater. Yet, I've NEVER seen anyone publish a comparision between the Langlier Index of a pool, and the index INSIDE the heat exchanger of a heater used on that pool. Take the pool above, with a 'theoretical' index of -0.1 . . . and add 30 degrees F.

Whoops!

All of a sudden, that nearly *ideal* index of -0.1 becomes a not so ideal index of +0.3 . . . and it does so, right where it can do some damage. So, now what should you do? Run a pool at around -0.4, so you can be fairly sure to maintain a SI of 0.0 or below in the heater? Or run an *ideal* SI of say, +0.2, and the HECK with the heater, at say, +0.5???

(If you notice, the recipes I give people tend to run low on the Langlier index. This is ONE reason why!)

There's more, of course. But I hope this explains adequately why I don't get all charged up about teaching all PoolForum users how to use the "Langlier" or "Ryznar" or "Hamilton" indices.

Ben
"PoolDoc"

[waterbear]

Bravo Ben! You reinforced some conclusions I had arrived at on my own from what I little could find out (Spent a lot of time researching boiler systems on the net!) and you cleared up some others for me. Thank you! I have gotten treated like a heratic when I have said to people that SI is intersting but don't loose a lot of sleep over it! (I dont DARE say it at the Pool store I work at part time....could cost me my job!) Am wondering though, what is your current take on high pH pools? From what I have been seeing the "Supreme pool algae reducers and water Opitmizers" (basically expensive borax) that are on the market have people running their pH on the high side which makes perfect sense if borates become a primary buffer system in the water.