Step 4 · Running Water Supply Lines

This is the step most people slow down on. Take it one move at a time — there’s no rush, and you can rewind the clip as many times as you need.

With the DWV system in place, you can now run the hot and cold water supply lines. First, shut off the main water supply to the house and drain the lines. Identify the nearest hot and cold supply lines to tap into, typically 3/4-inch main lines. Cut into these lines and install tee fittings. From the tees, run new 1/2-inch supply lines (PEX is popular for DIY due to its flexibility and ease of use) to the new bathroom. Route the lines through the wall studs to the locations for the sink, toilet, and shower valve. Use a PEX crimping tool to make secure connections if using PEX, or a soldering torch for copper. Secure the pipes to the framing using pipe hangers or clamps every 3-4 feet and at every change of direction to prevent movement and water hammer. Install stub-outs at the correct height for the toilet and sink, and install the shower valve body in the wall framing according to the manufacturer's instructions.