20.70.02.05

.05 Mains.

A. Depth of Mains. Water mains should be installed below the frost line or be otherwise protected to minimize the possibility of freezing and shall have not less than 30 inches of cover except where this depth is not feasible due to underground obstructions or rocky or hardpan conditions.

B. Dead Ends. The utility should design its distribution system so as to avoid dead ends in its mains. When dead ends cannot be avoided, the mains shall be flushed as often as necessary to maintain the proper quality of the water.

C. Segmentation of System. Valves shall be provided at reasonable intervals in distribution mains so that, in case of breaks or repairs, a minimum number of customers will be affected. When feasible, valves shall be provided in the mains at intervals not to exceed one continuous block or 500 feet, whichever is greater, except where a dead end run is not intended to serve any intervening customers.

D. Grid Systems. The distribution system should be laid out in a properly segmented grid so that, in case of breaks or repairs, a minimum number of customers will be affected.

E. Minimum Pipe Sizes. The distribution system shall be of adequate size and designed to maintain the pressures within the range required by COMAR 20.70.07.02. The pipe used in the system should be at least 6 inches in size. In special cases pipes of the sizes listed below may be installed. However, the maximum length from any connecting main at least 6 inches in size should not exceed the following:

(1) 1-inch ------------------ 150 feet;

(2) 1-1/2-inch -------------- 300 feet;

(3) 2-inch ------------------ 500 feet.