Installing a central vacuum system in an existing home can be a bit tricky, especially when it comes to installing inlet valves and PVC pipe in the walls. Here we show you how to do this if you have access from under the floor for the horizontal runs of pipe. If you do not have under-floor access, you may be able to modify these instructions to run the horizontal pipes through the attic. For installing a central vacuum system in new construction, a much easier job, see “Installing a Central Vacuum in New Construction.”

Start by selecting locations throughout the house for the vacuum system’s inlet valves. Space the inlets so the vacuum hose can reach every corner of the house. If you will be using an electric cleaning head, install an electrical receptacle within 6 feet of each vacuum inlet.

Mark the positions of the inlet valves on the interior walls at the same height as the electrical outlets. It is best to mount the receptacles next to wall studs, but it is not essential. Fittings are available for mounting valves directly to wallboard only. Use an inlet valve as a template to mark the wallboard for cutting the inlet hole.

Using a keyhole saw or wallboard saw, cut the hole.

Drill a 1/8-inch-diameter hole through the floor directly below each inlet hole (do this where the base shoe or the base molding will cover the hole). Push a wire through the bored hole so you can find it when you go under the floor.

Go below the floor and use the wire as a reference point for measuring the location for the pipe that will go up through the center of the wall. Cut a 2-inch-diameter hole up through the floor and through the 2-by-4 bottom plate of the wall, using a hole saw. You’ll probably have to do this in stages, using a combination of cutting with the hole saw and prying out chunks of wood with a chisel. Be sure to wear eye protection whenever using these types of tools!

Run a suitable length of the vacuum system pipe up into the wall cavity to the inlet hole and have a helper hold it there. Go back into the room above and cement on a 90-degree elbow, then slip the mounting plate through the hole and onto the elbow.