Tips for Planning New Plumbing Routes

House floorplan on large rolled paper with plumbing tools and materials on top

The Spruce / Michelle Becker

Any significant plumbing renovation job may require you to run new plumbing lines—whether this means replacing old pipes or running new ones for the first time. The first step in this kind of project is deciding where to run the pipes. This is often easier said than done because pipes will usually be concealed in wall spaces and covered by finished surfaces.

Two Common Ways to Run Plumbing

Most often it is easiest to simply run new pipes in the same cavities that contained the old plumbing. These spaces are already designed to allow for long, unbroken runs for pipes. When using modern plumbing materials, such as PEX tubing that is flexible, this is often the best choice. 

If the new plumbing plans call for changes in the fixture layout, it may be easier to run them up from the basement (if you have one). For example, instead of running a bathtub drain over floor joists, the drain line can be dropped into the basement and connected to the main drain line beneath the joists.


It is never advisable to notch out or cut into floor joists or support beams, as this may weaken the structural integrity of the building. Check with local building codes to determine the proper route for tackling any issues with support beams.

Alternative Ways to Run New Plumbing

These are additional ways to run new plumbing in your home. Remember, it's always easier to work in open spaces than in tight spots inside walls. And if you are ever uncertain about the legitimacy of a plumbing plan, check with local inspectors and city officials to ensure that everything you planned will be up to code.

Building a Wall Chase

A chase is a false wall that creates a cavity used to conceal plumbing. The chase can be stacked from floor-to-floor of the home. This allows plumbing to run from the basement to the attic. The chase is most commonly used for running new vent stacks. Similar to the chase is the soffit. Instead of running from floor-to-ceiling, a soffit runs across the top of a wall. Inside pipes can be run vertically to accommodate new plumbing.

Convert an Unused Laundry Chute

An unobstructed, unused laundry chute is perfect for running new pipes. They often run through most of the floors, usually terminating in the basement where connections are easier to make. The chute door can also be left intact and used as an access panel for shut-off valves.

Probing Wall Cavities

A long piece of pipe can be used to check prospective plumbing routes for any obstructions. Once the route is determined to be adequate, the pipe can serve as a guide for running larger- diameter plumbing. This is easily done by sliding the larger pipe over the guide pipe.