Always earth the unit as it will not function properly unless this done. The unit uses zinc as a sacrificial anode. The zinc combines with the calcium bicarbonate (limescale) to produce zinc carbonate. This is the non-adhering lime that prevents the usual problems associated with limescale. The reaction produces a small charge and the bond will conduct this electrical charge to earth.
It is not uncommon to see a white powdery residue on taps and shower screens after installation. This is normal and is the non-adherent lime. It can easily be wiped away with a cloth. Householders may feel that this is a sign that the unit is not working, but it is simply residue of the lime in its new non-sticking format. Please inform the householder of this prior to installation. If they would like additional proof that the unit is functioning correctly, refer them to the “Kettle Test” Link.