A.O. Smith Dscale Descaling Instructions page 12

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English
11. Leave the mixture in the appliance for 2 hours.
12. Open the drain valve.
Dispose of the mixture appropriately.
13. Check whether the limescale has been removed sufficiently, by looking at
the colour of the mixture. DScale is red. If the mixture has turned orange /
yellow, then limescale is still present. Repeat the descaling procedure.
14. Open the filler tap slowly and flush the device thoroughly with tap water.
Rinsing is required because DScale is acidic.
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A.O. Smith Dscale