Higher Calcium Levels & Stable pH

[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!

[smallpooldad]

Actually was not measuring at all but just walking by the unit and noticed that on a very sunny days this was occuring. It is happening again today, another gloriously sunny day with lower humidity thanks to mild trades around 12 mph.

As you know from the many previous post you have so quickly responded to I have a Pool Pilot Total Digital; it measures and reports pH constantly sampling all the water that passes through it. Most of the water is supplied to it by my roving pool cleaner, so presumably not local.

Maybe, as stated above, this information is not useful at all but I promised Chem Geek I would follow up. Or do you think it is better not to report these minor observations? I thought the China Shop was for this more esoteric stuff, or am I incorrect about this? If so I will stop posting observations.

The great thing about this though is that I am using less acid than I did before. Einstein is quoted as saying something like (although the context in which he meant this is debated) "Compound interest is one of the great wonders of the world'.

Bearing this is in mind a small seemingly insignificant savings can add up to significant savings over time and maybe as we have many sunny days - year round, at least in my local area, this is another great reason to live in Hawaii; saving money on acid. Also we rarely need pool heaters in winter so long as one covers. The other readings remain the same.

Thank you for your diligent attention to my posts. I am really learning more about pools and internet forum etiquette from you both; but most of all about chemistry from Chem Geek, as it applies to pools, and that's great.

[chem geek]

You can feel free to post anything esoteric or detailed you like in The China Shop, but you might still get opinions about it.

On intense sunny days there is more chlorine usage and the chlorine level probably drops a little (the SWG may make up for this when the sun isn't as intense). Chlorine usage is acidic. When the chlorine level rises back up, the pH should go back up. So you can see if your chlorine level varies with pH and you can use my spreadsheet to see if the amount is what you would expect. If not, then I don't know what it is -- it's certainly not anything large enough to worry about since it goes both down and back up.

Richard