Chemicals for hot tubs

[PoolDoc]

Nope. Adding sodium bicarb INCREASES the tendency of water to scale. There are various 'saturation' indices that give you some idea whether the water is likely to deposit calcium carbonate (often, the primary component of scale); these indices mathematically combine values for pH + temp + calcium + carbonates (alkalinity). Positive values tend to scale; negative values tend to dissolve calcium carbonate. In all of these indices, the index value INCREASES as any one component value increases.

Bicarb is added to pool and spa waters for 2 reasons: to 'balance' the saturation index, and to stabilize (buffer) the pH. For complex reasons, it does NOT work well for this purpose in heavily aerated spas ( this page explains http://www.poolsolutions.com/gd/lowe...p-by-step.html ).

If you can find it, borax would work better for you. It can help you adjust (raise) pH, buffer pH, and will not be aerated away like carbonates are. Even if not, I would recommend NOT adding bicarb to your pool, unless you have a concrete spa, have accurate test results for pH + temp + hardness + alkalinity, have calculated your S.I., and know you have aggressive water.

[chem geek]

Having the Calcium Hardness (CH) at 120-150 ppm can help reduce the amount of foaming (harder water foams less). The least expensive way to maintain the spa is the Dichlor-then-bleach method where you use Dichlor initially to build up a 30-40 ppm Cyanuric Acid (CYA) level and then switch to using bleach (using Dichlor once a month to make up for CYA loss). You need to get your Total Alkalinity (TA) down to around 50 ppm and use 50 ppm borates (say, from adding boric acid) as this will reduce the rate of pH rise. However, with chlorine, you need to add it to the tub every day or two. If you soak every day or two, that's no problem and you dose after each soak. If you only use the tub infrequently or just on weekends, then using bromine may be a better choice for you.