(a) Except as otherwise stated in subdivision (b) below, the water supply for new sprinkler systems may be tapped from the domestic water supply system provided the supply to the sprinkler system is of adequate pressure, capacity and reliability and provided that the following requirements are met:

1. (1) The sprinkler connection shall be made to a main or branch from a main with no intervening means of shut-off from the main.
2. (2) Water pressure from the main shall be sufficient to maintain at least 12 pounds per square inch at the highest sprinkler head. Where the water pressure is insufficient to maintain 12 pounds per square inch at the highest head but is sufficient to maintain at least five pounds per square inch at such head, an automatic booster pump shall be used as an auxiliary means of furnishing the required supply. The booster pump shall be caused to operate when the flow of water through any portion of the sprinkler piping is equal to or greater than that flowing from a single sprinkler head. The booster pump shall be capable of supplying sufficient water for a period of at least 20 minutes to at least 25 per cent of the total number of sprinkler heads at a pressure of at least 12 pounds per square inch at the highest sprinkler head. Such booster pump shall be so connected as not to restrict the flow of water in the system.