D.C. Mun. Regs. tit. 12, r. 12-F715
Strike Section 715.1 of the International Plumbing Code in its entirety and insert a new Section 715.1 into the Plumbing Code in its place to read as follows:
Sewage backflow. Where plumbing fixtures are installed on a floor with a finished floor elevation below the elevation of the manhole cover of the next upstream manhole in the public sewer, such fixtures shall be protected by a backwater valve installed in the building drain or horizontal branch serving suc h fixtures, or shall discharge to a sump complying with Section 712.3 and served by a sewage pump or ejector complying with Section 712.4. Plumbing fixtures installed on a floor with a finished floor elevation above the elevation of the manhole cover of the next upstream manhole in the public sewer shall not discharge through a backwater valve or a sump. This section shall not apply to replacement in kind of compliant plumbing fixtures.
Exception: Where the code official deems it appropriate for the protection of existing multi- level buildings in flood prone areas, the retrofitting of backwater valves to be installed in the building drain or in a horizontal branch serving fixtures on a floor with a finished elevation above the adjacent manhole in the public sewer shall be allowed, thereby allowing such fixtures to discharge through the backwater valve.
D.C. Mun. Regs. tit. 12, r. 12-F715