The First Rule of plumbing is that water flows downhill, but how can you get downhill from a basement? You must solve that problem if you want to put a bathroom there. All the fixtures you install have to drain somewhere, and according to the Rule, that somewhere has to be at a lower elevation than the fixtures.

One way to solve this problem is to do what I plan to do with my cabin — which is at a lower elevation than the septic system for the property — and use a macerating (up flush) toilet system. The one I intend to buy can handle waste from the toilet, shower and sink and feed it under pressure to a sewer pipe several feet higher in elevation.

If you have a sewer that runs underneath your basement floor, you can rely on gravity, but since most basement floors are concrete, it will take some extra work to bury your new pipes. They form what plumbers call the drain/waste/vent (DWV) system for your new bathroom, and installing them is the focus of this how-to. We won’t cover the water supply system, because you install it the same way you would in any other part of the house.

The materials you need for this project shouldn’t cost more than about $250, but you’ll save a lot by doing the work yourself. A plumber would typically charge between $1,500 and $2,000. Even if you run into complications requiring a plumber’s help, you’ll save money by doing most of the grunt work yourself.

Here’s a schematic of the floor plan for the project we describe. Note that the red lines are waste pipes, which connect to the sewer, and the green ones are vents that connect to the building’s vent system.