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Newbie ? On Vinegar/baking Soda


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#1 mrutkaus

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Posted 13 May 2008 - 09:48 AM

Just wondering, all these $14/bottle chemicals, what is the prevailing wisdom, especially from green people, about just using white vinegar to lower PH or baking soda to raise it?

And for that matter, laundry bleach for sanitizing?

A very open sensitive environmentalist here, a democrat and unitarian...

Mike
Winchester VA

#2 chem geek

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Posted 13 May 2008 - 10:59 AM

Mike,

Vinegar is a relatively weak acid and is in relatively low concentration of only 5% for white vinegar. It is acetic acid which is an organic acid. Generally speaking, one wants to avoid adding organic compounds into the spa water and acetic acid is an organic that will not get broken down readily by chlorine. It takes about 20 times the weight amount of white vinegar (5% acetic acid) to be equivalent to dry acid (93.2% Sodium Bisulfate). In terms of volume, it takes about 29 times the volume of vinegar to the equivalent volume of dry acid. Dry acid may be sold for pools and be less expensive than for spas, but the quantity will likely be more than you need. Another alternative for acid is Muriatic Acid, but this is very strong, can fume (especially the full-strength 31.45%), and would need to be measured out in very small quantities at roughly the same volume as with dry acid. Generally speaking, for spas, dry acid is the most convenient and safest to use (it is inorganic and adds to sulfates).

For raising pH, one can use Arm & Hammer Washing Soda (careful: not the laundry detergent) as this is just sodium carbonate (aka soda ash) and is in most (but not all) Spa Up products. This will raise the pH and also raise the Total Alkalinity (TA) some. Another alternative for raising the pH is 20 Mule Team Borax which is added by weight in double the amount as for Washing Soda (a little more than double by volume -- 2.15 times) and has half the impact on TA. Borax adds borates (mostly boric acid) to the water and is sometimes used in mineral waters.

Arm & Hammer Baking Soda is just sodium bicarbonate and will raise the TA more than the pH.

Clorox Regular and most off-brand Ultra bleaches are 6% sodium hypochlorite and are a source of chlorine. However, unlike Dichlor powder/granules, they do not add any Cyanuric Acid (CYA) when added to water. The usage of chlorine is acidic so using Dichlor regularly will help keep the pH more stable as the outgassing of carbon dioxide (from TA) tends to make the pH rise. So spas with an ozonator or aerating jets or other sources of significant aeration are not good candidates for using bleach as the pH rises too quickly. Though this can be mitigated through the regular addition of acid, adding two chemicals is too much trouble for most people. For spas that have minimal aeration, then some have found that bleach works well, but one should use Dichlor first for about a week to get some CYA (around 20 ppm or so) in the water and then switch to bleach. If one uses bleach without any CYA in the water, then this is over-chlorinating and will be too harsh on spa covers, swimsuits, skin and hair.

When adding any chemicals to the spa, one should do so slowly pouring over a return flow with the pump running (but jets off to prevent splashing).

I'm not so sure what you are considering "green" -- your examples seem to lean more towards reducing cost by using store-bought chemicals. Most people don't consider chlorine to be "green", probably due to the disinfection by-products that it can produce. An alternative that is more expensive but uses minimal chlorine is Nature2 which uses metal ions plus non-chlorine shock (potassium monopersulfate, MPS) as the primary source of sanitation with occasional shocking with chlorine. There is debate as to its degree of sanitation (though it's still far higher than not using a sanitizer and use of MPS with the Nature2 for sanitation is only for spas due to the higher temperature) and most people using Nature2 don't follow the instructions of having either chlorine or MPS at high levels before they soak (most people add either chlorine or MPS after they soak).

Richard

#3 mrutkaus

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Posted 14 May 2008 - 02:12 AM

Thanks for all the info,

Mike




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