D.C. Mun. Regs. tit. 21, r. 21-307
Fifteen inch (15 in.) meter pits shall be terra-cotta or fiber or plastic pipe. The frames and covers shall be in accordance with Drawing No. G-803-4A, latest revision.
Meters which are two and one-half inches (2 1/2 in.) or larger may be installed either inside or outside of a building. Such meters shall be installed at a location determined to be appropriate by the General Manager. The General Manager shall provide written notice of his or her approval of the location to the owner or occupant in advance of the installation.
Eighteen inch (18 in.), twenty inch (20 in.), twenty-four inch (24 in.), and thirty inch (30 in.) meter pits shall be terra-cotta, fiber, or concrete pipe. The frames and covers shall be in accordance with Drawing No. G-803-4, latest revision, and must be compatible with the Authority's Automated Meter Reading (AMR) technology.
Meter installation layout for compound meters located outside of a building shall be in accordance with Drawing No. G-808, latest revision.
A meter located inside a building shall have the same piping layout as indicated on Drawing No. G-808, latest revision, and shall have a floor drain within five feet (5 ft.) of the meter.
Meter installation layout for fire service type meters for use on fire and domestic combination services shall be in accordance with Drawing No. G-807, latest revision.
Meter installation layout for private and District regular service meters shall be in accordance with composite drawings showing meter settings five-eighths inch through two inches (5/8 in. -2 in.) and frames and covers for eighteen inch (18 in.), twenty inch (20 in.), twenty-four inch (24 in.), and thirty inch (30 in.) meter pits, Drawings Nos. G-815, G-803-4, and G-903-4A (latest revisions).
Meter installation layout for detector check fire service only shall be in accordance with Drawing No. G-813, (latest revision).
Each water meter that is three inches ("3") inches or larger shall be provided with a by-pass valve, and a valve will be placed on each side of the meter so that it can be removed without depriving the premises of water.
If placed on a pipe leading to a steam boiler or hot water boiler, or in any position where it may be exposed to a back pressure of steam or hot water, the water meter shall be protected by a check valve set between the meter and the vessel it supplies.
Whenever a check valve is installed on a private supply pipe to protect the meter from a back pressure of steam or hot water, a safety valve shall also be installed on that supply pipe between the check valve and boiler to relieve excessive pressure.
Before setting a water meter, the service pipe leading to it shall be well blown out in order to remove any accumulation of sediment.
The use of red lead in making joints in pipes connected with water meters is prohibited.
Pipe compound shall be applied to male pipe threads only.
Information and drawings pertaining to the installation of water meters pits and vaults is available from the Authority.
D.C. Mun. Regs. tit. 21, r. 21-307