The Dry Pipe Automatic Sprinkler System

The Dry Pipe Automatic Sprinkler System is similar to the wet pipe automatic system except that there is no water in the riser above the dry pipe valve. In a dry pipe automatic sprinkler system, the riser is pressurized with air or nitrogen. The air or nitrogen pressure is typically 15 to 20 pounds above the public water system distribution system static pressure. The pressurized riser keeps the dry pipe valve closed. The dry pipe sprinkler system is connected to the public water system and there is typically a fire department connection connected to the riser. The fire department connection is installed upstream of the dry pipe valve and downstream of the main control gate valve. The fire department connection is equipped with a check valve. Another check valve is installed on the public water system connection before the main control gate valve. This check valve is not an approved backflow prevention device for cross-connection control. An evaluation of the fire system connection to the public water system distribution system shall be made to determine the appropriate type of backflow protection required for this system, if any. Studies conducted and published by reputable firms show that dry pipe automatic fire sprinkler systems do not require additional backflow protection for cross-connection control.