D.C. Mun. Regs. tit. 12, r. 12-E1007
Strike Section 1007 of the International Mechanical Code in its entirety and insert a new Section 1007 in the Mechanical Code in its place to read as follows:
Return water connection. The return water connection to every low pressure steam or hot water heating boiler shall be arranged to form what is known as a "Hartford Loop" so that the water cannot be forced out of the boiler below the safe water level. This connection shall be installed on each boiler, with the inside bottom of the return pipe close nipple, where it connects to the equalizing loop, at the same level as the top of the bottom nut of the water gauge glass.
Equalizer pipe. Each boiler shall have a separate equalizer pipe installed between the bottom opening of the boiler and the boiler stop valve, when used. The equalizer pipe shall not have a valve in it at any point and shall not be used as a means to connect two or more boilers together below the water line. Equalizer pipe sizes shall not be less than the schedules indicated in Table 1007.2.
TABLE 1007.2 EQUALIZER PIPE SIZES
GRATE AREA (square feet) | S.V.R.C. a (pounds per hour) | PIPE SIZE (inches nom.) |
Under 4 | 250 or less | 1 1/2 |
4 to 15 | 251 to 2000 | 2 1/2 |
Over 15 | 2001 or over | 4 |
For SI: 1 square foot =0.0929 m2, 1 inch = 25 mm, 1 pound/hour = 0.4536 kg/h.
Stop valve. When a stop valve is used in the return line of the loop it shall be located within 6 feet (1829 mm) of the floor. A drain valve shall be provided at the lowest point of the return line. Galvanized pipe and fittings shall not be used in any part of the equalizer pipe or return line.
Public water system mechanical feed. Each boiler shall be provided with a mechanical feed line supplied from a reliable public water system. The feed line shall not connect directly into any part of a boiler exposed to the direct radiant heat from the heat source. It shall be connected to the equalizing line between the boiler and the condensate return connection and shall have a check valve in the line as close to the boiler as possible.
Boiler feed line. The boiler feed line shall be designed so as to adequately take care of the maximum demand of the boiler.
Public water system shut-off valve. All connections from the public water system shut-off valve shall be made of brass pipe with screwed fittings. Tubing shall not be used.
Exceptions:
Condensate return pump. A condensate return pump shall have capacity to supply the boiler or boilers it serves with sufficient water to maintain a normal water level when the boilers are operating at maximum capacity. When more than one boiler is served by the pump, the condensate return line shall be arranged to supply all boilers adequately.
Stop valve. A stop valve shall be installed in each supply and return connection of two or more boilers connected to a common system. When a stop valve is used in the supply pipe connection of a single boiler, there shall be one used in the return pipe connection and vice versa. If there are multiple branch connections, each one shall be valved. When stop valves over 2 inches in nominal size are used they shall be of the outside screw-and- yoke type.
Stop valve location. Stop valves shall be located as close to the boiler as possible and when over 7 feet (2134 mm) above the floor shall be made accessible for operation by means of either (1) a permanent steel ladder and platform; or (2) a chain or motor operated mechanism.
Blow-off connections. Each boiler shall have one or more blow-off connections fitted with straightway valves connected directly with the lowest water space. Plug or bob cocks shall not be used. A discharge pipe shall be run to the floor, full size, with an "ell" at the bottom to direct the water away from the operator, or to a blow-off tank. A "tee" fitting shall be used at the boiler in order to provide a cleanout for the line. Blow-off valves and discharge pipes shall not be smaller than the schedule indicated in Table 1007.9 based on the equivalent direct radiation rating of the boiler. If a surface blow down is used, it shall be run full size to the floor with an "ell" at the bottom, or to an approved drain.
TABLE 1007.9 BLOW-OFF VALVES AND DISCHARGE PIPES
BOILER RATING (square feet E.D.R.) | Valve and Pipe Size (inches nom.) |
Under 1000 | 3/4 |
1001 to 3500 | 1 |
3501 to 8500 | 1 1/2 |
8501 and over | 2 |
For SI: 1 square foot = 0.0929 m2, 1 inch = 25 mm.
Wash-out and hand-hole openings. All wash-out and hand-hole openings shall be accessible and shall not be obstructed or blocked by pipe or other obstacle. Capped pipe nipples and plugs shall be installed in wash-out openings.
Cross connections. There shall be no cross connection below the water line, for any purpose, between two or more boilers.
D.C. Mun. Regs. tit. 12, r. 12-E1007