How To Move a Toilet

During a bathroom remodel, maintaining the bathroom's basic footprint is essential to controlling costs and mess, as well as keeping on schedule. But sometimes a bath remodel calls for a change in the layout. Moving the toilet, even just sideways or a few inches over, is one of those changes in the bathroom layout that is sometimes necessary.

Trying to relocate a toilet is not a change to be taken lightly. But if needed, it can be accomplished with substantial plumbing work and a great deal of peripheral work, such as opening up a floor or ceiling, rerouting pipes and drain flange, and re-installing the toilet and other fixtures. This is normally a job for a construction crew and professional plumber, but some very skilled DIYers can successfully do the work. Taking on the job requires a good understanding of the basic steps, as well as considerable experience with all the skills involved.

How a Toilet Is Moved

Moving a toilet is not so much about moving the actual fixture—in fact, installing a toilet is a simple job that takes less than an hour—as it is about moving the drainage and the water supply plumbing to the new location. Once all of the plumbing is in place, installing the toilet is a relatively easy task.

Moving the Toilet Drain

The below-floor toilet drainage pipes are wide in diameter—usually 3 inches—and difficult to route around or through flooring joists. Other services running underneath floors further complicate matters: water supply pipes, electrical cables, insulation, cross-bracing for the joists, recessed lights, and more.

Also, toilet drainage pipes are gravity-fed, which means that they must drop at a vertical rate of 1/4-inch for every horizontal foot. While usually this can be managed, it can limit the distance of the new toilet location, since the toilet needs to remain close enough to the vent stack or main drain to accommodate the necessary slope.

If possible, then, try to plan your new toilet location so that the new drain can run in the spaces between joists, and try to avoid notching out joists to run the pipes. Do so may require adding structural reinforcement if the alterations are substantial enough to compromise the strength of the floor framing.

Moving the Toilet Water Supply

A second part of the project is less difficult: running a water supply line to the toilet. Toilets need a supply of fresh water to fill the tank after every flush. Because these pipes are smaller, they can more easily be routed through joists or even inside of wall systems. A relocated supply line might even tap into the existing toilet supply line and send it to the new location. Bendable plastic PEX pipes make this job easier for do-it-yourselfers when compared to the older classic method of running copper pipes and sweat-soldering the connections.

About This Project

The project described here does not move the home's main drain/vent system, as this feature is shared by other drainage pipes for other fixtures and sometimes even by other rooms. In our example, the toilet is moved 5 feet (many bathrooms are 5 feet wide) for a total drainage line vertical drop of 1 1/4 inches. The drainage line and water supply line run in the spaces between parallel joists—not across the joists, which makes for a more complicated installation.

Our example assumes that the existing waste-vent stack and toilet drain are made from ABS plastic pipe—which is the most common scenario. If your waste-vent stack is made from a different material—cast iron or PVC plastic are other common possibilities—this may slightly change how to connect the new toilet drain to the stack. For example, you will need to use PVC fittings if you are connecting to a PVC waste-vent stack.

Before You Begin

Depending on where your toilet is being moved to, the precise drain fittings needed may vary. Be prepared to use additional PVC or ABS fittings as necessary to route the toilet drain to the waste-vent stack. It is critical, however, that the flow into the waste-vent stack use the gradual bends provided by sweeps and wye fittings, not sharp elbows that interfere with smooth drain flow.

Use a roughing guide to provide the dimensional data and exact location for the waste and water piping from the finished walls, allowing you to prep the piping before relocating the fixture. This is called a "layout." A good mechanic always does a layout prior to starting the work to check for obstructions such as beams or electrical wiring, and also to correctly locate the main stack. Knowing this information may alter your layout of the fixture and can save you from either buying the wrong fixture or starting the work at all.

When To Call a Professional

If your home is built on a concrete slab, you will typically need to call a professional to move a toilet. The process is more involved and requires destroying the slab to access the necessary parts to relocate a toilet.