At first glance, switching your toilet and sink when remodeling your bathroom looks like a fairly easy project. How hard can it be to move the sink and toilet and plop them down in opposite places? In fact, while it looks deceptively difficult, toilet installation is a very easy do-it-yourself job.

The problem, though, lies in not the surface elements–sink and toilet–but in the underlying plumbing. Moving plumbing drives up bathroom remodeling costs in a big hurry.

Specifically, there are two issues to look at. First issue is providing hot water to the new sink location. The second issue, it moving the toilet drain/vent system and its wastewater system.

If your house is on a concrete slab foundation, you’ll have to break up the concrete to install the new drains. If it’s a raised foundation, you can run the new pipes under the floor joists. Plumbers can access this through the crawl space or basement. That’s the easiest option. If the bathroom is on a second floor, the same floor-joist rules apply. The only difference is you’ll have the added expense of demolishing sections of the first floor ceiling and then rebuilding it. Not impossible, but messy and costly.