On wet fire systems, the pressure gauge located above the clapper of the alarm valve indicates the ________.

On wet fire systems, the pressure gauge located above the clapper of the alarm valve indicates the ________.

• A. System pressure
• B. Alarm pressure
• C. Supply pressure
• D. Main pressure

Answer: (A)

In a wet pipe system, the alarm valve (with the clapper) holds back water in the piping until a sprinkler head is activated. The gauge mounted above the clapper is connected to the water-filled system side of that valve, so it shows the system pressure—the pressure inside the sprinkler piping downstream of the valve. This reading reflects how much pressure is actually available to the sprinklers once the valve trips. It is not the upstream supply pressure in the feed line, which would be on the other side of the valve, and it isn’t an alternate “alarm pressure” reading.

In a wet pipe system, the alarm valve (with the clapper) holds back water in the piping until a sprinkler head is activated. The gauge mounted above the clapper is connected to the water-filled system side of that valve, so it shows the system pressure—the pressure inside the sprinkler piping downstream of the valve. This reading reflects how much pressure is actually available to the sprinklers once the valve trips. It is not the upstream supply pressure in the feed line, which would be on the other side of the valve, and it isn’t an alternate “alarm pressure” reading.