I cannot change the PH value

Maybe you know the problem: You measure a pH value of over 7.6. You add pH-Down and the next morning you still measure a too high pH value. Meanwhile, maybe your water is slightly cloudy?

This is probably because the alkalinity of the bathing water has not been set correctly.

Alkalinity is the water's pH buffer - the greater the buffer, the greater the water's resistance to changes in pH.

Too high alkalinity (>150 mg/l CaCO3) means that you cannot change the pH value. If you add pH-Down, the pH value is "pushed" back again.

Alkalinity can be reduced by Alka-Down.

Too low alkalinity (<60 mg/l CaCO3) means that the pH value cannot be controlled and the pH value varies widely. At the same time, too low alkalinity can cause corrosion (rusting) of your spa. Alkalinity can be increased by Alka-Up.

Feel free to use the hot tub calculator, you will know exactly how much to add of either Alka-Down or Alka-Up.

NOTE! Remember, when adding treatment to the spa, the circulation pump (massage pump) should be running, but the air inlet (air screws on the top of the spa) should be closed.

This is how the alkalinity is adjusted:

1. Measure the alkalinity (TA) using the test equipment. 
2. Adjust the alkalinity to 80-120 mg/l. Take the help of the hot tub calculator to measure the correct amount.
3. If alkalinity is to be lowered, it is important that the pump is switched off so that the water is completely still before Alka-Down is added.
4. Wait 3-4 hours and check the alkalinity again.
5. Measure the pH value with a digital SmartTest or tablet tester (do not measure the pH value with sticks, it is not accurate enough). Then adjust the pH value to 7.0-7.4 with either a pH-up or pH-Down.