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All sprinkler pipes and fittings shall be so installed that they can be completely drained. On wet pipe systems, sprinkler pipes may be installed level. In dry pipe systems and portions of pre-action systems subject to freezing, branch lines shall be pitched at least one- half inch per ten feet and mains shall be pitched at least one-quarter inch per ten feet.
Drain pipes for system risers and mains shall be not less in size than given in the following table:
Size of Riser or Main | Size of Drain |
Two inches or less | 3/4 inch |
Less than four inches but greater than 2 inches | 1 1/4 inches |
Four inches or greater | Two inches |
Where sectional or floor control valves are provided, they shall be provided with a drain sized as shown in the above table to drain that portion of the system controlled by the sectional valve.
Where installed underground, drains shall be galvanized with galvanized fittings or other corrosion resistant material. Where exposed to the weather they shall be fitted with hoods or elbows turned down to prevent stoppage with ice.
Drain pipes shall be so arranged as not to expose any portion of the sprinkler system to frost and shall be so connected that they will not overflow domestic or other piping. Direct connection shall not be made between sprinkler drains and sewers.
On wet systems all piping for sprinklers in excess of 20 which may be trapped, shall have a separate drain valve and drain connection; piping for 20 or less sprinklers shall be provided with non-ferrous drain plugs except the drop to an individual sprinkler head. On dry pipe systems, piping for sprinklers in excess of 20 which are trapped shall be equipped with a drain consisting of two one-inch valves separated by a 12-inch length of two-inch in diameter pipe. Where fewer than 20 sprinklers are trapped the drain may consist of a valve not smaller than one-half inch.
(Prior code § 91-25; Amend Coun. J. 10-30-96, p. 31216, § 1)