A water closet is the plumbing and building code term for a flush toilet: the fixture that removes waste with a flush of water into the drainage system. On drawings and fixture schedules it is usually abbreviated WC. In the UK and some other countries, “WC” also means the small room that contains a toilet.
Codes use the term so specifications are precise. A “lavatory” in code language is a hand-wash basin, not a toilet.
Types of water closets
| Type | Description | Typical use |
|---|---|---|
| Tank-type (gravity) | Tank stores water that flushes the bowl by gravity | Homes and light commercial |
| Pressure-assist tank | Pressurized vessel inside the tank gives a stronger flush | Busier washrooms without flushometers |
| Flushometer (flush valve) | No tank; valve on the supply line delivers the flush | Commercial and public washrooms |
| Floor-mounted | Bowl sits on the floor over a floor flange | Most residential work |
| Wall-hung | Bowl is mounted to the wall on a concealed carrier | Commercial, healthcare, easy floor cleaning |
Installation notes
- Rough-in: in North America the distance from the finished wall to the centre of the drain is commonly 12 inches, with 10 and 14 inch models available. Confirm against the fixture cut sheet before the slab or floor is poured or framed.
- Carriers: wall-hung WCs need a carrier anchored to the floor and enough wall depth to house it.
- Flush volume: in the US, federal rules have capped new toilets at 1.6 gallons per flush since the 1990s, and WaterSense models use 1.28 gallons or less. Local codes may be stricter.
- Accessibility: accessible WCs need specific centreline distances from the side wall, seat heights, grab bars and clearances under the ADA or the local accessibility code.
- Venting: each WC connects to the drainage and vent system so its trap seal is protected.
Related terms
Related templates and guides
- Washroom partitions: the definitive construction guide
- Water closets and urinals AutoCAD blocks
- Quality checklist: plumbing and sanitary works
Frequently asked questions
Why is a toilet called a water closet?
The name dates from the 1700s, when flushing toilets were installed in a small room or closet and flushed with water, unlike privies and dry closets. Codes and drawings kept the term, and in the UK the abbreviation WC is still common for the room.
What is the difference between a water closet and a lavatory?
In plumbing codes and on drawings, a water closet is the toilet and a lavatory is the hand-wash basin. In everyday British English ‘lavatory’ can mean the toilet or the room, which causes confusion, so specifications use the code meanings.
What is a flushometer water closet?
A flushometer (flush valve) water closet has no tank. A valve connected directly to the water supply delivers the flush, so it needs adequate supply pipe size and pressure. Flushometers are common in commercial and public washrooms because they recover quickly between uses.
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