Higher Calcium Levels & Stable pH

[smallpooldad]

Chem Geek,

Just drained the pool down to get Calcium at 375 and a pH of 7.5, so we will see. Anyhow should I drop dead tomorrow at least the pool person that my wife will hire will not be able to give her some "Cock and Bull" story about the Calcium being too high.

Unless of course he is really good looking and young. That again could seriously influence the story/numbers.

I will let you know how it goes.

Aloha

[CarlD]

Unless of course he is really good looking and young. That again could seriously influence the story/numbers.

I will let you know how it goes.

Aloha

"Go home to your wife. Better still, let me go home to your wife and apart from the improvement, she'll never know the difference. Pull over to the side of the road and let me see your marriage license!"
-- Prof. Quincy Adams Wagstaff, better known as Groucho Marx, (From "Horse Feathers")

[smallpooldad]

Well the pH is holding fine with the following numbers. Small amounts of acid are being inputed into the pool by the PoolPilot Digital input face but the tank seems to have used relatively little acid once the Alk got to 80. The tank is mixed 1 part muriatic to 4 parts water.

Here are the numbers:

Measurement
Measured pH 7.5
Total Alkalinity (ppm CaCO3) 80
Free Chlorine (ppm Cl2) 6.0
Cyanuric Acid (ppm CYA) 35
Calcium Hardness (ppm CaCO3) 400
Total Dissolved Solids (ppm) 3,450
Total Sulfate (ppm SO42-) 0
Total Borate (ppm Boron) 50.0
Total Ammonia (ppm Nitrogen) 0.0
U.S. Gallons 10,000
Temperature (oF) 83

Total Chloride (ppm NaCl) 3019
Carbonate Alkalinity (ppm CaCO3)61.9
Langelier Saturation Index (LSI)-0.09
% HOCl (vs. Total Free Chlorine)1.3%
OCl- (as ppm Cl2) 0.099
HOCl (as ppm Cl2) 0.080
Calcite Saturation Level (CSL) 0.63
Calcite Saturation Index (CSI) -0.20

A pH of 7.5 seems less irritating to the eyes. These seem fairly ideal numbers. One reason the pH holds so well is the pool is covered except from 5pm to 9pm for swimming. If the cover is left off over night the pH rises to 7.55-7.6 according to the digital control, mostly to 7.55

[chem geek]

Thanks for the update. At least this now makes more sense -- keeping the pool covered and having more stable pH is directly related to carbon dioxide outgassing and wouldn't have anything to do with the CH level. So though I don't know why the pH seemed to be more stable at higher CH, at least keeping on a cover makes it stable as we would expect.

[smallpooldad]

Further follow-up.

Increased Calcium to 425. The strange thing is that although the pool starts of at a pH of 7.5 if it is very, very sunny the pH actually drops if the cover is off to about 7.45. Have no idea why this happening. Later in the day (5 hours later at about 5 pm) it returns to 7.5, sometimes it might get up to 7.52. This only occurs on very sunny days. SWG runs from 11 am to 3 pm.

This is confirmed by my friends pool that also displays the same tendency. The only difference in his pool is that he has no borates and the calcium is 375. His SWG runs from 8:30 am to 4:30 pm.

I do not expect a reply but I thought it might be useful to you to follow-up, maybe not.

Aloha and thank you for all your kind and polite replies.

[CarlD]

That variation in pH is totally statistically insignficant. You could play around with various hypotheses, but my guess is the water is moving around and reacting to the air, out-gassing a little in the local area you're testing (as in aeration), re-mixing a little unevenly, etc.

Sometimes we over-measure and over-organize. One company that made sort engines as a gag produced a calendar that was completely alphabetical for days of the week and months of the year...
Friday, Monday, Saturday, Sunday, Thursday, Tuesday, Wednesday...
April,August, December, February, January, July, June, March, May, November, October, September
Kinda useless but very funny!

[waterbear]

T
Sometimes we over-measure and over-organize.

I couldn't agree with your more, Carl!