Why Don't People Use Pool Chemicals In Spas

[chris@cyclecat]

Why don't spa owners use liquid chlorine and so forth in tubs like a regular pool?

[chem geek]

Why don't spa owners use liquid chlorine and so forth in tubs like a regular pool?

Some do. Some spa owners use Dichlor and/or bleach. Others use bromine and some use Biguanide (PHMB aka Baquacil). There are advantages and disadvantages to each. Other pool chemicals, specifically baking soda (sodium bicarbonate or Alkalinity Up) are also used for pH buffering. Calcium is not usually added since tubs are not usually plaster.

[Brulan1]

Why don't spa owners use liquid chlorine and so forth in tubs like a regular pool?

Some do. Some spa owners use Dichlor and/or bleach. Others use bromine and some use Biguanide (PHMB aka Baquacil). There are advantages and disadvantages to each. Other pool chemicals, specifically baking soda (sodium bicarbonate or Alkalinity Up) are also used for pH buffering. Calcium is not usually added since tubs are not usually plaster.

You should have a calcium hardener to the water especially when dealing with bromine because it prevents excessive foaming. Generally when you use bromine you constantly have to add alkalinity to set the PH in range. When you constantly do that your TDS builds and foaming starts. TO prevent excess foaming, hardener should be added.

[chem geek]

You should have a calcium hardener to the water especially when dealing with bromine because it prevents excessive foaming. Generally when you use bromine you constantly have to add alkalinity to set the PH in range. When you constantly do that your TDS builds and foaming starts. TO prevent excess foaming, hardener should be added.

You are right. I forgot about that. However, you don't need to saturate the water with calcium carbonate so don't need Calcium Hardness (CH) to be near 300. I believe waterbear found that a CH of somewhere around 100-150 works well to reduce the foaming. Again, thanks for reminding me about the need for at least some calcium.

[Whoneedsavacation]

I also understand that bromine (or at least the acid that is formed when using bromine as a sanitizer) is more effective at the higher temperatures than chlorine alone. Thus you can use less of it and still have a well-sanitized tub.

[chem geek]

I also understand that bromine (or at least the acid that is formed when using bromine as a sanitizer) is more effective at the higher temperatures than chlorine alone. Thus you can use less of it and still have a well-sanitized tub.

Actually, that is not correct. Both are more effective at higher temperatures. The issue isn't effectiveness, but the fact that the chlorine can outgas faster than bromine (at equivalent concentrations) so can get reduced in concentration and THAT would make it less effective. This problem can be lessened by using some CYA in the water as by using Dichlor as a chlorine source, at least for a short while (about a week; possibly two) and then switching to bleach so as to not accumulate too much CYA.