Toilets are the largest single use of water in American homes. In the United States it has been illegal since January 1, 1994, to make toilets for residential use that use more than 1.6 gallons per flush, a restriction extended to toilets for business and industry in 1997. (What do you suppose an industrial strength toilet is?)
Two types of toilet seats are sold in the United States, matching two different toilet bowl shapes. If the distance from the centers of the toilet seat mounting holes to the outside front of the bowl is 16½ inches, the toilet requires a “round” toilet seat. If this distance is 18½ inches, an “elongated” or “elliptical” seat is needed.
The rim height is the distance from the finished floor to the rim of the bowl. Rim heights of 14, 15, 17, 18 and 19 inches are available.
Accessibility requirements (ADA) are based on seat height, which of course is higher than the rim height. In the United States, toilets in public rest rooms are required to have a seat height of 17 inches to 19 inches (432 to 483 mm) above the finished floor.¹ A rim height of 16½ inches is sufficient to meet this requirement. For residential dwelling units, the legal minimim is relaxed to 15 inches.
1. Section 604.4, 2010 ADA Standards for Accessible Design. See also ANSI 117.1a 2003.
The standard “rough-in,” the distance from the wall to the center of the waste pipe in the floor, is 12″; however, toilets requiring 10″ and 14″ rough-ins are also made.
If you are interested in toilet design, you may want to read about the "unit" unit.
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Last revised: 16 March 2012.