SWG Cost Calculator - seeking feedback

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mitchellb said:
I do not think this is correct. As you lose chlorine through outgassing from the pool, you will end up with a relative increase in NAOH as a byproduct of the electrolysis reaction. This gradually raised the pH in SWG pools.

The cost of lowering pH on a regular basis should be factored in here and can be substantial in some cases. I have to add quite a bit of MA regularly.
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Unless the SWG is installed incorrectly, chlorine gas loss never happens. The chlorine gas produced by the SWG has a very high solubility in pool water and completely dissolves and hydrolyzes before ever leaving the return lines. The bubbles that come out are hydrogen gas bubbles because hydrogen gas has very low solubility in water. When chlorine reacts with anything in the water, it gets reduced back to chloride ion. Those reactions all produce a proton (H+) and are acidic. Therefore the total hydrogen ion change is zero.

SWGs are pH neutral.
 
JoyfulNoise said:
Unless the SWG is installed incorrectly, chlorine gas loss never happens. The chlorine gas produced by the SWG has a very high solubility in pool water and completely dissolves and hydrolyzes before ever leaving the return lines. The bubbles that come out are hydrogen gas bubbles because hydrogen gas has very low solubility in water. When chlorine reacts with anything in the water, it gets reduced back to chloride ion. Those reactions all produce a proton (H+) and are acidic. Therefore the total hydrogen ion change is zero.

SWGs are pH neutral.
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Perhaps my use of "outgassing" is not responsible for the majority of chlorine loss, but there is no doubt that chlorine is consumed by our pools. The UV rays from the sun cause significant chlorine loss along with the process of sanitation and creation of CC. When we lose chlorine from the pool, this causes the pH to rise.
 
mitchellb said:
When we lose chlorine from the pool, this causes the pH to rise.
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Actually, chlorine loss is net acidic. It lowers pH.

Any pH rise that you are experiencing is not from the SWG.

It's probably from high TA or plaster dissolving due to low CSI.

Note: This discussion should not continue in this thread. Any further discussion should be in a new thread.
 
mitchellb said:
Perhaps my use of "outgassing" is not responsible for the majority of chlorine loss, but there is no doubt that chlorine is consumed by our pools. The UV rays from the sun cause significant chlorine loss along with the process of sanitation and creation of CC. When we lose chlorine from the pool, this causes the pH to rise.
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There is no chlorine loss at all. The chlorine is simply undergoing a change in oxidation state from it's oxidizing/sanitizing form (Cl+) to its reduced form (Cl-). The amount of chlorine does not change except for the fact that more chloride builds up over time in pools that are treated with chlorinating compounds as opposed to a salt water pool where the chloride level is fixed and the cell is doing all the work of turning chloride (Cl-) back into chlorine (Cl+). The formation or introduction of chlorine in the water raises the pH but then the oxidation & reduction reactions that occurs lowers the pH. Sunlight (UV) does not cause chlorine loss - the UV photons simply reduce the active chlorine (Cl+) to it's reduced form (Cl-). Again, no change in chlorine.

If you interested in further understanding the details of pool water chemistry, I suggest you read this thread - Pool Water Chemistry
 
lightmaster said:
Is there a way to change the purchase price for your SWG? Got my RJ-45 on sale, so I didn't pay the full price .
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Yep, you can scroll down on the 'User' sheet to row 44 or so, and enter it as a user-defined SWCG. It will then be Custom1, Custom2 or Custom3, depending which line you use. Then select your defined one (say, Custom1) in the drop down box at cell L10.

Thanks, JoyfulNoise, for asking that the chemistry be discussed elsewhere. My intent is for the calculator to be neutral with respect to some of the factors that are more complicated. If you feel your pool will need more acid because of SWCG aeration, you can have that in the figures, or zero it out. User-controlled :)

Green Goblin and others, I've added higher CYA loss to my to-do list, simply because of splashout/draining taking more CYA with it, when using TFPC guidelines. It could also be argued chemically, but in the spirit of user-control, it's worth considering.

Metal corrosion is difficult because all pools are pretty salty. The miles per jug was all I could think of that most anyone could relate to, lol. Some people go and get 20 jugs only when they're at Wal-mart anyway, so they might zero it out. Others go to a specific store and return an empty carboy and get it re-filled, so I just gave them a variable. I actually hoped it might help the odd pool enthusiast convince their financial partner (or controller) across the dining table of the merits of their proposal :)

And to anyone, don't hesitate to ask, argue, remind or cajole! That's how I can make it better :)
 
I've added a variable on the 'User' sheet so that people can allow for any concern about increased acid consumption arising from switching to SWG. Like others, it can be zeroed out to remove the cost.

I hope the calculator helps reassure people that costs are similar, and helps them understand what happens to their cash. For me, the convenience and avoided shopping/lifting/hauling is all the reason I need :)

Thanks again for your feedback so far.
 
Green Goblin, thanks again. CYA is added now, using an initial 35 ppm uplift for converting from liquid to SWG. The extra cost to cover splashout, backwash and overflow of the extra CYA is also added. I chose 35 ppm to cover the difference between TFPC recommended CYA for SWG vs. bleach

I'm hoping to make it as user-friendly as I can. Please let me know any aspects that make the calculator hard to use or not as obvious as it could be. It's hard to find the bad bits after working with it too much :)

Here are the links to keep them handy:

SWCG FC Cost Calculator.xlsx - Google Drive

SWCG FC Cost Calculator.xls - Excel 97-2003 version - Google Drive
 
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