Installing A Basement Bathroom

Installing a basement bathroom is not a project that can be completed by a beginning DIYer. This an advanced, multi-stage project that requires planning, determination and know-how. We’ve written this post as your guide to getting started, because it helps to know what stages lie ahead. You can use this post as your rough plan, but each step involves many mini-steps. Don’t get started on this project until you really understand the full extent of those mini steps.

Plumbing the Basement

Installing basement plumbing after the house has been built can be challenging. Above grade plumbing relies on gravity to carry waste water away from the home. Below grade plumbing installed after the fact is sometimes too low to rely on gravity.

    1. Find your home’s main line. To do this, you can use a line locator and metal fish tape, which is a tool that can be rented from online sources. To show you how to do this, we found this handy video online:

  1. Pencil in the location of the fixtures relative to the main line.
  2. Determine the possible slope of the lines from fixtures to the main line. The lines need to slope downward 1/4 inch per foot. Determining the possible slope can be complicated. Take a look at this website for detailed instructions. At this point, you may determine that the slope will not be enough to drain the toilet. To fix this, you can do one of two things. Either:
    • Move the fixtures to a point where it’s possible to slope the drain lines enough that they’ll drain on their own.
    • Install an above ground solution. Check out this site for a lengthy rundown of possible above ground solutions.

    If you find out that the drain lines from your fixtures to the main line can be sloped properly, move on to the next step.

  3. Cut through the concrete from the future fixture drains to the mainline. You can use a sledgehammer or a combination of circular saw and sledgehammer for this part. Check out this online video:


  1. Use a reciprocating saw to cut into the main line and splice a Y-fitting into the line.
  2. Run the pipes from the main line to the fixtures. You can see this process up close on this website.
  3. Run lines to the plumbing vents elsewhere in the house. This process has been documented here.

Installing Floor, Fixtures and Electrical Wiring

Once you’ve plumbed in the bathroom, the rest of the work is much like installing a bathroom above ground. Unless you’re a certified electrician, you should hire one to do your electrical work for you.

Next, install the floor tiles. This part is relatively easy compared to what you’ve been doing. Get the floor tile down before installing fixtures, because your fixtures will need a surface to sit on. You can check out the process in this video:

Once the floor and the electrical work is finished, move on to installing the toilet, vanity and sink. For more information on that process, check out this website where the entire process of installing a basement bathroom was documented.

This sounds like a lot of work, doesn’t it? If you’re not up to the challenge, don’t feel bad. Just call Terry’s Plumbing. We can plumb your basement and install the fixtures for a reasonable rate.