Endless Cycle: PH - Alk

[Sabot]

First off... my pool is still someone new: Filled with water on Nov 1, 2007. I am also heating my water with solar.

Now to the meat of the topic... It seems that I am in an endless cycle of adding Muriatic Acid and Baking Soda... If I let the pool alone and there is no rain, the PH will rise above 8 in a few days. (Normal?) So I add the amount of acid by using the Pool Calc. Likewise, if I did do nothing to the water, the Alk will drop. I am trying to keep the Alk between 80-100ppm. Adding one drops the other, endless! Being new to pool ownership and what I have read here, this seems to be part of pool ownership.

Any comments on what I might be doing wrong/right? I am wanting to continue to learn and keep my water crystal clear and without smell. BBB has been a champ so far.

Below is my testing data for the month of April:
Date-Water Temp-TC-FC-CC-PH-Alkalinity-CYA
4/1/2008 78 2.07 1.92 0.15 8.2 103 40
4/4/2008 74 0.88 0.82 0.06 8.4 98
4/6/2008 82 8.27 8.27 0 7.8 89
4/7/2008 85 7.89 7.89 0 7.9 70
4/8/2008 84 5.09 5.06 0.03 8.3 88
4/9/2008 80 4.02 4.02 0 7.7 83
4/10/2008 81 2.59 2.51 0.08 7.6 67
4/11/2008 82 9.85 9.58 0.27 7.9 92
4/12/2008 82 6.77 6.73 0.04 7.5 73 38
4/13/2008 75 5.59 5.41 0.18 7.5 73
4/13/2008 81 3.5 3.35 0.15 7.5 79
4/14/2008 79 3.65 3.55 0.1 7.9 82

Below is my chemical usage data for the month of April:
Date-Liquidator-Bleach6%-Baking Soda-Muriatic Acid
4/1/2008 0 0 0 60
4/4/2008 0 0 0 60
4/5/2008 0 182 0 20
4/8/2008 0 0 0 65
4/9/2008 0 0 0 32
4/10/2008 0 0 128 32
4/11/2008 0 0 0 50
4/12/2008 0 0 64 32
4/13/2008 3 0 64 32
4/14/2008 3 0 64 32
-------------------------------------------------------
182oz 320oz 415oz
(I turned off my Liquidator to trouble shoot an issue, turning it back on April 14. )

 

[duraleigh]

Sabot,

Unfortunately, I am out the door in about two minutes so didn't have time to look carefully at your well-compiled data but two comments:

1. pH and Alk move WITH one another....Alk up & pH up or both down but not the way you describe. one of the chem gurus will address that soon.

2. You must be testing with some type of strips and a digital readout to get those numbers. Generally, that's not the best testing method for consistency and accuracy. A plain old drops based test gives pretty consistent results. Testing procedure may have something to do with your pH and Alk issue.

 

[Guest]

I would look at your testing procedure first. Are you using a LaMotte ColorQ by any chance? If so then you have to realize that even though it is reporting results down to 1 ppm (precision), it's accuracy (repeatable results) is not that small for many of the tests such as CH and TA. This does not make it bad, you just have to learn how to read it. If your variance in TA is les than about 10 ppm I would not worry about it at all. Looking at your results I would have to say that your TA has been fairly stable.

 

[Sabot]

Good morning all!

I use both the ColorQ and TF100. I don't own any strips. If I really want to go for a ride, I visit the local pool stores. The ColorQ and TF100 are real close. I use the ColorQ for daily (or so) checks and the TF100 for weekly checks or to double check when the numbers look off.

 

[Guest]

Based on the numbers you posted I would have to guess that they were done by the colorQ. Realize that the colorQ is probably BEST at chlorine and pH and the other readings actually have a wider variance. If they are within 10 ppm of each other I would consider them to be about the same.

As far as your results vs. the pool store, I would trust yours over theirs! If it were MY pool I would use the color Q for quick checks of chlorine and pH as long as I was not shocking and use the TF100 for weekly tests of chlorine, pH, and TA. I would only test CH and CYA monthly unless I suspected some problem with either.

Sometimes LESS data will give you a better picture of your pool chemistry.

 

[Sabot]

Is the pool consuming to much acid or baking soda or is this normal amounts?

Granted, I have been spending more time forcused on the PH/Alk then I have over the winter. The water is very clean looking and has almost no smell to it. Nothing is growning from what I can tell. The Liquidator is taking care of the chlorine, now the only two items that I have been adding of late is acid and baking soda.

Why don't the chain pool stores have more complex testing machines? I am assuming it's costs.

 

[JasonLion]

The test results for TA appear to have a fair bit of test variance in them, which I would expect with the ColorQ. The actual TA wouldn't jitter like that, that is the imprecision in the tester. Don't worry about +-15, that is normal for the TA test.

You might want to try letting the TA go down a bit further. With the Liquidator, or a SWG, you can usually let TA go down to the 60 to 70 range without problems and sometimes lower. Lowering TA will reduce the rate of PH drift, particularly with a spa.

 

[Guest]

If you want to reduce your acid usage then LOWER your TA to around 60-70 ppm and DON'T lower your pH below 7.6. When it hits 7.8 then lower it back to 7.6 and not lower. Adding acid to a plaster pool is a normal thing when using unstabilized chlorine. Every pool is different so it's hard to say what is normal but I can tell you this, the more baking soda you add when not really needed, the more acid you will need to add. Adding borates can help stabilzie the pH even more. Your pH rise is being caused by the aeration from your water features. Running the TA low will help with that somewhat but you pool will always probably have an acid demand.

As far as testing equipment in pool stores, Taylor labs are probably the BEST, IMHO, but they are slow. We use a LaMotte Waterlink Express (A $1000 colorimeter conntected to a computer) and the LaMotte UDV reagent vials. It is fast (I can run a battery of 8 tests, including copper and iron, in 5 minutes) but it has limitations (which is why I also have a Taylor kit to titrate TA and CH when needed and an OTO kit to make sure I don't have bleachout of the DPD when it reads low and I have reason to suspect that it isn't).

 

[Sabot]

Will do. I will change my ideal range between 50-70. I was trying to keep it between 80-100. During the winter, it hovered around 50. Maybe that was the key. I don't mind chemical usage, just wanted to double check with you guys to ensure I was not getting off the BBB track.

The folks with the Liquidator recommend a lower PH level: 7.2 - 7.4 to reduce the scaling on the unit. I have not had any luck with keeping the pool that low. I reduce it down that low when I plan to add a a large amount of baking soda which is not often. I am trying to adjust smaller amounts daily then one big adjustment to reduce the swings.

Side note, I am not using the water features yet until the weather becomes a bit warmer. The spa is a stand alone unit, not a part of the pool.

You guys are awesome!