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Engineering ToolBox > Drainage Fixture Unit Values (DFU)
The Drainage Fixture Unit Values (DFU) are defined by the Uniform Plumbing Code (UPC), and can be used to determine the required drainage capacity from the fixtures and their service systems.
| Individual Appliance, Appurtenance or Fixture | Minimum Size | Drainage Fixture Unit Values DFU | |
| (inch) | Private Installations | Public Installations | |
| Bar sink | 1 1/2 | 1 | 1 |
| Bathroom (water closet, lavatory, bidet and tub or shower) | 6 | - | - |
| Bathtub | 1 1/2 | 2 | 2 |
| Bidet | 1 1/4 | 1 | |
| Bidet | 1 1/2 | 2 | |
| Clothes Washer | 2 | 3 | 3 |
| Dishwasher, domestic | 1 1/2 | 2 | 2 |
| Drinking fountain | 1 1/4 | 0.5 | 0.5 |
| Floor drain | 2 | 2 | 2 |
| Shower | 2 | 2 | 2 |
| Laundry tub | 1 1/2 | 2 | 2 |
| Lavatory | 1 1/4 | 1 | 1 |
| Bar sink | 1 1/2 | 1 | |
| Kitchen sink, domestic | 1 1/2 | 2 | 2 |
| Laundry sink | 1 1/2 | 2 | 2 |
| Service or mop basin | 2 | 3 | |
| Urinal | 2 | 2 | 2 |
| Water closet with gravity tank | 3 | 3 | 4 |
| Water closet with flushometer tank | 3 | 3 | 4 |
Note that this conversion is only true for one or a few fixtures. Since the fixtures in a system are never used all at the same time, the total units (capacity) achieved by adding the numbers for all fixtures must be compensated for intermittent use if we want a realistic estimate of the total drainage load.