It is not clear if you want to use the 'same' water pipes for drinking/showering and electricity.
Assumption 1: Same pipe with water for both water and electricity
Because if you would touch water that has too much voltage/current, you die.
Actually, what happens is:
- Assuming the water has a voltage of 220 V (or 120 V in the US)
- As soon as you touch the water, there will be (in most circumstances) a connection between the water (110/220 V) and ground (GND).
- The electricity will flow through your body
- Depending on the resistance more or less current will start to flow: through your body.
- This high likely is way too much for your heart, or if not, burn wounds will occur.
Even if the water would have the voltage of a battery, you don't want to brush your teeth with water having a voltage different from ground.
Assumption 2: Different pipes with water for water and electricity
Water has much more electrical resistance than copper, which means it would cause a lot of voltage reduction after long pipes filled with water.
I think this is the main reason, other reasons can be (thinking out loud):
- Water pipes can leak if broken
- If a water pipe (plastic) is broken, dirt can get in, resulting in no or less good conductivity.
- A copper wire always has a certain diameter which is fixed, with water it depends on the pressure of the pipe
- Pressure is needed to keep the water on such a pressure there are no bubbles.
- Water can freeze, possibly resulting in different conductivity properties
- You need multiple pipes, if a pipe breaks the chance is that the water will be 'mixed' resulting in a short cut. A clean copper wire cut will not result directly in a short cut.
Assumption 3: Only inter-house/building pipes
(meaning only using water to distribute electricity within a single building/house).
- Water generally doesn't go to the same end location as electricity. You don't need a socket near the toilet flush, and you don't need a tap near your TV set. So this is pointless, except maybe for the kitchen (see comment of dim below).