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From the 2018 UPC Illustrated Training Manual, Chapter 8, INDIRECT WASTES

804.1 Standpipe Receptors. Plumbing fixtures or other receptors receiving the discharge of indirect waste pipes shall be approved for the use proposed and shall be of such shape and capacity as to prevent splashing or flooding and shall be located where they are readily accessible for inspection and cleaning. No standpipe receptor for a clothes washer shall extend more than 30 inches (762 mm), or not less than 18 inches (457 mm) above its trap. No trap for a clothes washer standpipe receptor shall be installed below the floor, but shall be roughed in not less than 6 inches (152 mm) and not more than 18 inches (457 mm) above the floor. No indirect waste receptor shall be installed in a toilet room, closet, cupboard, or storeroom, or in a portion of a building not in general use by the occupants thereof; except standpipes for clothes washers shall be permitted to be installed in toilet and bathroom areas where the clothes washer is installed in the same room.

One of the primary duties of the design professional and the plumber concerning indirect waste is to ensure that the receptor is large enough in physical dimensions and in pipe size to accept the waste flowing into it. The receptor must be deep and wide enough so that there will be no overloading or splashing on the floor that could cause a slip hazard. The size of the receptor should be determined using the parameters set forth in Section 702.0, Fixture Unit Equivalents, Table 702.1 and Table 702.2(2).

The clothes washer standpipe is considered an indirect waste receptor, not a fixture tailpiece, and, as such, has specific requirements for its use. The minimum and maximum elevations of the trap and the standpipe allow for flexibility in installation resulting in a total rise above the floor between 24 and 48 inches, the two possible extremes.

A 24-inch flexibility in the height of the standpipe is helpful, for example, when installing a standpipe with a wash basin (see Figure 804.1b). In this example, it would be good practice to elevate the height of the standpipe above the flood level height of the wash basin. In the event of a blockage downstream, the waste would back up in the wash basin before it would overflow through the standpipe. The allowable range of height for the trap and standpipe will allow the clothes washer standpipe to terminate above an adjacent sink (see Figure 804.1a). Also, the 18-inch minimum height of the standpipe intends to prevent the possibility of the clothes washer’s pumped waste from overflowing the standpipe.

The 2018 Uniform Plumbing Code Illustrated Training Manual is available for purchase here.

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