The Rough-In Standards for a Water Closet

The correct name for a toilet is "water closet.

Distance to Wall

" Architects and manufacturers specify what the dimensions are for water closets, and what the installation dimensions are. The installation dimensions are critical, since they specify exactly where the outlet opening (called the flange) should be, along with where the water supply should be. Furthermore, minimum spaces are specified, since cabinets or sinks cannot interfere with a water closet's usage.

The distance from the wall to the middle of the flange opening is 12 inches. Water closet openings are standardized, and this measurement is an industry standard. If you wish to allow a little bit more room from the tank to the wall, this measurement can be a maximum of 14 inches. Any more than 14 inches, and the toilet will appear to be out in the middle of the bathroom.

Water Supply

The location of the water supply outlet is standardized as well. From the floor to the middle of the supply pipe, the distance should be 8 1/4 inches. From the center line of the water closet, it is 6 inches away, toward the left. To lay this out on the wall, first draw the center line of the closet. Draw a parallel line 6 inches away toward the left. On the offset line, draw a cross line 8 1/4 inches up from the floor. The middle of the supply pipe should come out where the crossed lines are. These dimensions can be varied a little bit, since most water closet supply lines are flexible to allow for variations in mounting. Do not vary more than an inch on either measurement, though, since codes may not allow for a wide variance. For example, a stud may be right where the hole is supposed to go, so you have to move the hole over a little bit.


You must allow enough room around the water closet for people to use it comfortably. Allow a minimum of 24 inches from the front of the unit to the nearest object, such as a sink. For the side clearance, allow a minimum of at least 15 inches away from the center line. If any of these clearances are less, a person will be cramped into a small space when using the water closet.

About the Author

Tony Oldhand has been technical writing since 1995. He has worked in the skilled trades and diversified into Human Services in 1998, working with the developmentally disabled. He is also heavily involved in auto restoration and in the do-it-yourself sector of craftsman trades. Oldhand has an associate degree in electronics and has studied management at the State University of New York.