Raising Total Alkalinity Vs. Adjusting Ph

[Whoneedsavacation]

My book came, but I'm disappointed in the amount of detail on water chemistry. Sigh. Is there a good reference out there at a sort of Scientific American level of technicality? I want to know a bit more about WHAT chemicals and HOW they work and HOW to decide how much of WHAT to use.

I've noticed the total alkalinity in my spa beginning to drift down. My startup package came with two products for adjusting pH -- "Spa Up" and "Spa Down". Nothing in any of the references I have says anything about what to use to adjust total alkalinity, although the book agrees with this board that you should adjust it first before worrying about pH. It does NOT say what to use. Upon closer examination, the Spa Up is sodium bicarbonate -- baking soda. A search on this board turned up some posts suggesting use of baking soda (as bought at the grocery) for adjusting total alkalinity. If I want to raise TA by something like 60 ppm in a 300g spa, how much should I add? What is different in the composition of pH increasers and TA increasers when bought commerically. Are the commerical products any more pure or otherwise more desirable than grocery store products?

If I dump baking soda in and the TA goes up, but so does the pH, what do I do next? Wait 24 hours, or add acid?

Sorry to be so dense!

[chem geek]

You aren't being dense at all and are asking excellent questions.

This link to the stickies at TroubleFreePool gives a lot of the info on various chemicals, what they are, what they do, etc. Click on the sticky "BBB and basic chemistry explained". As for a calculator, click on the stick "Pool Calculator".

Your Spa Up product is most likely sodium carbonate which is the same as in most pH Up products and is the same thing as Arm & Hammer Super Washing Soda (careful: this is not the laundry detergent). The Spa Down product is most likely sodium bisulfate. Because the Spa Up product is sodium carbonate, it will raise both pH AND alkalinity. It is technically identical to adding lye / caustic soda / sodium hydroxide AND Alkalinity Up / Baking Soda / Sodium Bicarbonate. And yes, Arm & Hammer Baking Soda is identical to Alkalinity Up products.

If by commercial products you mean brands specifically targeted to pools and spas and sold in such stores compared to grocery store brands, there is absolutely no difference with most of them. Some pool/spa store products have extra items in them, but the basic item is identical and usually you don't want the extra items anyway. Usually, such "extras" are found in the chlorine products, not in the pH or alkalinity adjusting products.

If you want to raise the pH without raising the TA as much, then you can add 20 Mule Team Borax and you add twice as much by weight as you would if you used sodium carbonate. If you want to be even more "pure", then you can use Lye / Caustic Soda / Sodium Hydroxide to raise pH, but for a spa that is VERY difficult to measure since it's so powerful. If you want to raise your pH with NO change in Total Alkalinity (TA), then just aerate your water, which with a spa should be very easy to do by running the jets. The outgassing of carbon dioxide will raise the pH with no change in TA (the spa water is intentionally over-carbonated, like a tasty beverage though not nearly as carbonated, in order to provide a pH buffer).

Richard

[104 Degrees]

Richard

I would like to thank you for all the help in the past

John 104

[anewspa]

Richard,

Yes Thank You. You have been very helpful!

L anewspa

[navsav]

Richard nice response. I have another question for you.

Di-chlor is not cheap if you get the 99 percent pure stuff. A salesman at the pool place told me I could use the 60 % stuff for the spa - is this ok? Whats the other 40 percent made of - will that clog my filters or cause other issues?

[chem geek]

I don't know what is in the other stuff. I you have a specific brand, then I can try and look up the MSDS to see what is in it or you can read the ingredients label, but it may just say "inert ingredients". Dichlor isn't that expensive -- you can get it a Leslie's online for $2.60 per pound and for spa amounts that's way more than you need. You should only use Dichlor for about a week after a fresh water fill and then switch to bleach after that. Otherwise, the Cyanuric Acid (CYA) level will keep building up making the chlorine less and less effective and unable to kill the bacteria that causes hot tub itch. Most people don't get that, however, so you can just use Dichlor if you want -- I'm just giving you a conservative option.

The most common form of Dichlor is dihydrate (as opposed to anhydrous) and I didn't even know they made any Dichlor less than 100% pure.

[tony]

Richard nice response. I have another question for you.

Di-chlor is not cheap if you get the 99 percent pure stuff. A salesman at the pool place told me I could use the 60 % stuff for the spa - is this ok? Whats the other 40 percent made of - will that clog my filters or cause other issues?

Some pool places just don't give good information. All Dichlor is 99% pure. The available chlorine of the two Dichlors is 56% and 62%. Both will add almost as much CYA as chlorine to your water.

[chem geek]

Ah thanks for thinking about that. Yes, the dihydrate form of Dichlor, which is the most common, is 55.4% available chlorine (usually quoted as 56% as you indicated) while the anhydrous form of Dichlor is 64.5% available chlorine (quoted as 62% in your example). The ingredients label will list the weight percentage of each chemical and probably says nearly 100% of "Sodium dichloro-s-triazinetrione dihydrate" or something like that. There may be a separate entry that says "XX% Available Chlorine".

And yes, for every 1 ppm FC added by Dichlor, it will also add 0.9 ppm to Cyanuric Acid (CYA) levels.