Kitchen plumbing packs a lot into a small cabinet: supply lines, drain, dishwasher connection, disposal wiring-adjacent plumbing, and sometimes a water line for the fridge. Sink installation runs $200–$600+, dishwasher hookup $150–$350. This section covers what each piece costs, how they connect together under the sink, and the common leak points to check yearly.
The under-sink audit
Once a year, empty the cabinet and look with a flashlight: supply valve corrosion, damp particleboard, loose slip nuts, and disposal discharge leaks. Ten minutes catches the leaks that rot cabinets silently for years.
Dishwasher drainage done right
A high loop or air gap in the dishwasher drain hose prevents dirty sink water from siphoning back into the dishwasher — required by code in most places, skipped in most DIY installs. Our guide shows both methods.