LC113 -- Why does a chalky/hard coating form on the surface of the whirlpool tub?

Chalky / hard coating on the tub surface

Why does a chalky/hard coating form on the surface of the whirlpool tub?

The cause is probably chalkiness - you probably have hard water.


Lower the pH of the water to 5.0 for one to two days. The low pH will cause the limescale to dissolve again.


  • Never let the pH value rise above 7.4. Always lower it in time with pH-Minus.
  • Add more SpaBalancer SoftWater to the water.
  • Use partially softened water for filling (water hardness 7° German hardness is ideal)
  • If you have hard water (more than 14° German hardness - you can ask your water supplier for the water hardness), you should lower the pH value to 5.0 for 2 days every 4 to 8 weeks and then increase it again to 7.0. This will dissolve any limescale deposits in the pipes. Be sure to use the SpaBalancer pH-Minus Liquid for this, as it contains special limescale dissolvers. You can use any commercially available pH lifter to increase the pH.

Do not remove hard deposits in the whirlpool tub mechanically

Under no circumstances should you remove the rough coating mechanically. This coating also sits in the pipes and would lead to biofilms if you do not remove it there. The rough coating consists of lime. By lowering the pH value of the water, it becomes "acid" and thus dissolves the basic lime. A pH value of 5.0 is not corrosive to the technique for this short time. You can also use the whirlpool during this time. The skin has a pH value of 5.5 and tolerates this water well.

When the limescale has disappeared, increase the pH value again to 6.5 to 6.8. If the pH value is below 7.0, no limescale can form. You also don't have to worry about corrosion at 6.5 to 6.8. Since the SpaBalancer products, unlike chlorine, do not add acid to the water, the water is not corrosive to the technology at these pH values.

You can find more information on water hardness, limescale and pH value here

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