Step 1: The digging
Step 2: The Toilet and the Sewer
Step 3: The wiring
THE WATER WIRING:
For the water wiring, you put a button in the wall, reverse the signal and plug it to the water piston.
THE LAVA WIRING:
The lava wiring is very simple, as it is slower, a button doesn't work, so we use a lever plugged directly to the piston.