Dear Chem Geek, I've downloaded a copy of your PoolEquations.xls file and as a non practicing Chemical Engineer and pool owner I am beyond impressed. If I may ask a few questions:

1) is there a thread with basic instructions?
2) if I press either the "Calculate pH/TA" or any fo the "Calculate" buttons for that matter I can tell that it is going through the iterations but when finished it simply sets the Goal equal to the Intitial and then all the necessary additions are zero. I assume something is malfunctioning?

I made the spreadsheet for myself so that I could do a bunch of pool water chemistry calculations so it was not designed for general use and doesn't have instructions. The Pool Calculator is the easy-to-use calculator to use though it does not calculate pH adjustments or effects as accurately when they are larger or outside normal pool parameters (or when Borates are present). I'll give some basic instructions here that should help you use the spreadsheet if you want to continue to do so.

When you are using the spreadsheet to figure out amounts of chemicals to add, then you enter in data into the Initial and Goal columns in the upper section of the spreadsheet. When you have Goals that are different than Initial, you will see that in the lower section of the spreadsheet in the blue sections (in the same column as Goal) that numbers appear. These are reasonably accurate, but you then have two choices to get an accurate number, especially for acid/base/buffer amounts. Normally for pH adjustments you want the TA to float so you would click on the "Calculate Acid/Base/TA" button in the lower section. This is the most common button to use and will adjust the TA goal automatically to show you the result of adjusting the pH using the chemicals you have indicated and the resulting numbers in the yellow-orange Inputs section may be quite different than initially shown in the blue section. If instead, you really did want to figure out how to adjust the TA as well as the pH, you would click on the "Calculate Acid/Base/Buffer" button in the lower section which will mostly copy the numbers from the blue area into the yellow-orange Inputs section with some minor adjustments. However, note that it may indicate that you need to aerate the water to outgas carbon dioxide. Generally speaking, you don't use this latter button very often.

The other way to use the spreadsheet is to have the Initial and Goal be the same and add chemical additions in the yellow-orange Input column in the lower section. Then click on the "Calculate pH/TA" button and the Goal values will be changed to reflect your chemical additions (other Goal items in addition to pH and TA will also be updated appropriately.

With either of the above approaches, you need to set the combo box controls (scroll lists) to the appropriate chemicals you are using (e.g. Muriatic Acid vs. Sulfuric Acid or Soda Ash vs. Borax).

You can do sequences of operations, though sometimes this gets tricky. For example, you can see how much acid is needed to compensate for adding 50 ppm Borates. You would first change the Goal for Total Borate to 50 ppm (assuming the Initial is 0). Make sure the control near the "Base to add to increase pH" section is set to "20 Mule Team Borax (Sodium Tetraborate Decahydrate)". You will see that there is a recommended amount of base to add in the "Base to add to increase pH", but if you scroll down you will see that it also shows up in a section called "BORATES" or "Increasing Borates" which is where you should type the number from one of the blue lines into the yellow-orange line (it doesn't matter which line you use -- they are just different units of measurement, but you can only use one at a time). After typing in any entry, you must press Return on the keyboard. Now click on the "Calculate pH/TA" button and you will see the effects of adding borates which should show a much higher pH and TA in the Goal section (TDS also increases). Now scroll back up to the top and change the Goal pH to 7.5. Now click on the "Calculate Acid/Base/TA" button. In the Inputs (and Input Equiv.) column you will see the amount of acid needed to achieve that pH and you will also see that the TA in the Goal column has been adjusted and is now about 5 ppm higher than the Initial. This is because Borax does not raise the TA very much as it mostly remains as Boric Acid (near a pH of 7.5).

In the above example, you didn't have to do it in two steps and could have skipped clicking on the "Calculate pH/TA" button. You would then get the answer directly on how much acid to add, but wouldn't see how the Borax alone would increase the pH and TA before the acid addition.

In another example, let's see the effects on pH of shocking with high levels of chlorine. Add a higher amount of "Free Chlorine" in the Goal column so that it's, say, 20 ppm FC higher than the Initial column (or you can set Initial to 0 and then set Goal to 20). Scroll down to the "Added Chlorine" section and add whatever type of chlorine you want, say bleach or chlorinating liquid, by typing in a number in the yellow-orange section that is the same as shown in the blue section and then press Return. Then click on the "Calculate pH/TA" button and see that the pH and TA rise quite a bit. You can then lower the Initial pH and click on "Calculate pH/TA" to see how this lowers the resulting pH after chlorine addition. You should see that lowering the pH to 7.2 before adding chlorine keeps the pH below 8.0 at around 7.9 whereas starting with 7.5 has the pH go to nearly 8.4.

Hopefully, that gives you enough to get started. Let me know if you have further questions or want to do something more advanced.

Richard

Just want to say I've been using the spreadsheet for the last two seasons and love it.

I have high alk in my fill water and need to reduce TA constantly. The pool calculator can't tell me how much acid to add to reduce TA so I always use the spreadsheet.

thanks for a great tool!

dave

Where is this spreadsheet???

The spreadsheet is always accessible at a link near the end of the first post in this "Pool Water Chemistry" thread. The link to the spreadsheet is here. Again, it is not for novice users.

Actually, if you are wanting to lower the TA, the amount of acid it takes to do so is at a fixed relationship. If you use The Pool Calculator and put in an amount of acid (near the bottom of the web page), it will tell you how much the TA is lowered. For every 10 ppm TA to lower, it takes 25.6 fluid ounces of Muriatic Acid (31.45% Hydrochloric Acid) in 10,000 gallons. Of course, that tells you the total cumulative amount of acid you would need, but doesn't tell you how much it takes to lower the pH to 7.0 or 7.2 in the first step nor how much to add after aeration to get from, say, 7.4 to 7.2, etc. So that's where the spreadsheet can be useful until we get these much more complicated calculations in The Pool Calculator at some point. Nevertheless, The Pool Calculator was updated a while back to roughly help with these calculations and isn't that far off (unless you have Borates in the water).

Richard

Chem Geek, thanks so much for the instructions. This is exactly what I needed. Thanks again for all your contributions to the forum.