Tap water conducts electricity whereas distilled water does not because:

i. Tap water has certain salts and chemicals dissolved in it.

ii. When electricity is passed through tap water, these salts and chemicals change into ions.

iii. These ions are responsible for the conduction of electricity in tap water.

iv. Whereas distilled water has no such salts and chemicals dissolved in it.

v. When electricity is passed through distilled water, no ions are formed. Thus, no conduction of electricity in distilled water.

Hence, due to the presence of dissolved salts in tap water, the tap water conducts electricity and distilled water due to the absence of these salts do not conduct electricity.