We have had a Hot Tub for 30+ years. Read lots of articles, bought lots of chemicals. Now we have a simple formula for care.

Our water comes from a well, it's hard and contains iron. If your water is brown it may be iron or tannin's. An easy test for iron - 1/2 bucket of water add 1/4-1/2 cup bleach, leave overnight.
Bleach will oxidize the iron, leaving clearer water. You can also test with Iron Out, but do not use Iron Out in Hot Tub.

Only use liquid chemicals. Powdered chemicals will eventually make the water cloudy requiring you to drain and refill.

Filling - - (Our tub is 1022L or 270 Us Gal.)
• Use an old filter, add about 1 cup of bleach and run pump. Repeat until water is clear. Replace filter.
• If you have Iron(water is brown) start with 2 cups of bleach.
• We know our PH is high, ∴ we start with 1 cup of Muriatic Acid.
• Using test strips determine the PH. Add chemical to obtain neutral PH. Best not to use 'til PH is stable.
  • Baking soda (powder is ok) to raise. Muriatic acid to lower.
  • Take your time, test again after 8-10 hours.
  • If your PH strip shows very high or low, your PH may be higher/lower that the strip can show.
  • High PH (8.0+) will reduce the effectiveness of bleach.

Using
• After using Hot Tub add 1/4-1/2 cup of bleach daily.
• Once a week add 1/2-1 cup of bleach.
• Use test strips daily until you get into a working routine.
• Check PH every week and adjust. Bleach will tend to increase the PH.

Other
• If the tub develops a cloudy condition that bleach will not remove add clarifier.

Almost all skin reactions are NOT caused by bleach, the culprit is PH.    PH, either high or low will burn your skin.

We use our Hot Tub almost daily 8-9 months of the year and have no tub related reactions. Controlling Ph is the key to a happy Hot Tub!