What is the reason why there is electricity in the tap water at home?

There is no leakage protection switch and no repeated grounding wire. If not, there is a fire line touching the water pipe. Turn off the main power. If there is still electricity, it may be that the fire line of someone else's home or the main line touched the tap water pipe. If not, it is that your fire line has touched the water pipe. If you don't understand, please ask a professional electrician to repair it. Remember the danger.