TA reading question

[just ducky]

I'm two days into having the new spa up and running, and I've been working on the water chemistry.  When I was talking with my dealer just after I bought the spa, he specifically said I should work to get the TA in the 120-150 range.  Yes, this is what he said...I asked him a couple times and took notes.  When I read the info in my owners manual and on the test strip package, it says ideal TA is 80-100.  My dealer has been in business for years, and has a reputation in the area for knowing his stuff.  But now I'm second-guessing him.  Any thoughts?

[just ducky]

I just tried the spa calculator that someone posted previously.  When I plug all of my current numbers in, with my TA up around 120, it tells me the levels are good.  So I guess I answered my own question.

Here's another newbie question that I don't quite get...I initially had very high levels of TA, so as instructed I've been using "Spa down", and apparently now have TA in control.  However the PH level is still high, so my instructions say to keep using Spa Down every couple hours, and continue doing tests, until the PH is acceptable.  But won't this also keep bringing down the TA?  Am I going to cause problems with the TA by continuing to use this product?

[chem geek]

If your spa tends to go high in pH, then lower the TA level.  If you try and keep a higher TA level then the pH will tend to rise and you'll be in a catch-22.  You basically need to adjust your TA to a level where the pH is roughly stable.  There is no single TA level recommendation one can give for this since it depends on the chemicals you are adding to the spa and on the amount of aeration.  Generally speaking, when using Dichlor or some MPS brands, then a higher TA level (100-140 ppm) is needed to keep the pH stable.  When using a hypochlorite source of chlorine (e.g. bleach), then a lower TA level (60-80 ppm) is needed to keep the pH stable.

Pools and spas are intentionally over-carboanted and Total Alkalinity (TA) is mostly a measure of that carbonation (technically, it mostly measures bicarbonate).  Just as a carbonated beverage that you stir will outgas carbon dioxide and lose its carbonation, the same is true for a pool or spa.  This outgassing causes the pH to rise (and the TA to remain the same for technical reasons I won't get into here).  When you add acid to the water, this lowers both the pH and the TA.  This is why adding acid and aerating is an easy way to lower the TA (especially if this is done at a lower pH which makes the process go faster).

If you want to balance your saturation index, then you adjust your calcium hardness (CH) last, after you've adjusted your TA to get your pH to be stable.

Richard

[just ducky]

If your spa tends to go high in pH, then lower the TA level.  If you try and keep a higher TA level then the pH will tend to rise and you'll be in a catch-22.  You basically need to adjust your TA to a level where the pH is roughly stable.  There is no single TA level recommendation one can give for this since it depends on the chemicals you are adding to the spa and on the amount of aeration.  Generally speaking, when using Dichlor or some MPS brands, then a higher TA level (100-140 ppm) is needed to keep the pH stable.  When using a hypochlorite source of chlorine (e.g. bleach), then a lower TA level (60-80 ppm) is needed to keep the pH stable.

Pools and spas are intentionally over-carboanted and Total Alkalinity (TA) is mostly a measure of that carbonation (technically, it mostly measures bicarbonate).  Just as a carbonated beverage that you stir will outgas carbon dioxide and lose its carbonation, the same is true for a pool or spa.  This outgassing causes the pH to rise (and the TA to remain the same for technical reasons I won't get into here).  When you add acid to the water, this lowers both the pH and the TA.  This is why adding acid and aerating is an easy way to lower the TA (especially if this is done at a lower pH which makes the process go faster).

If you want to balance your saturation index, then you adjust your calcium hardness (CH) last, after you've adjusted your TA to get your pH to be stable.

Richard

That actually made sense to a newbie like me    Thanks.