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Electrical & Plumbing for Finished Basements

A basement finishing project is much like finishing an entire floor on your home. Local building codes vary by community and your building department is the final authority on what is correct and legal. They will have specific requirements for the plumbing and electrical systems. Bathrooms, wet bars and kitchenettes require water supply, waste, drain and vent plumbing and every finished room has specific electrical requirements.
  1. Water Supply

    • Bathrooms and other rooms or features that require water will have their own plumbing. Newer materials such as PEX and CPVC make doing your own plumbing easier, but these materials are not allowed in some communities. Copper plumbing provides the water supply for most homes. The large pipes for the water heater make good connection points for basement plumbing. To reduce sudden temperature changes, use 3/4-inch pipe to distribute water to different rooms, and 1/2-inch pipes to make specific fixture connections.

    Sewer Connections

    • If you're adding a bathroom in the basement and the builder did not include a toilet or shower rough-in, you will cut the floor, break up the concrete and add the drain pipes. Each basement plumbing fixture must connect to the home's plumbing vent pipe. The septic system or municipal sewer line enters many newer homes above the level of the basement floor. Waste and water are routed into an enclosed pit and stored there until it reaches a set level. A pump activates which ejects the sewage into the main drain pipe of the home.


    • Plan on a different circuit for each room. A subpanel adds room for more circuit breakers if the main service panel doesn't have enough room for each new branch circuit. Bathrooms, kitchenettes and wet bars need separate 20-ampere circuit breakers, 12-gauge wire and ground fault interrupter receptacles. Other rooms with standard branch circuits can use 14-gauge wire, 15-ampere breakers and standard outlets. Check local codes for specific basement wiring guidelines.

    Building Codes

    • Basement plumbing and wiring are not much different than the rest of the house. The same rules and codes apply with few exceptions because some local codes may have different requirements for basements. Unfinished basement space doesn't have many requirements for electrical and plumbing beyond appliances such as furnaces, water heaters and sump pumps. Some localities have restrictions that prevent the addition of certain fixtures in unfinished spaces. Finished basement space has specific requirements for receptacles, lighting and plumbing fixtures which must adhere to building codes.