Dry System Valves

The Most Reliable Dry System Valves

Reliable® dry system valves are designed to protect areas subject to temperatures below 40°F (4°C). Dry sprinkler systems have compressed nitrogen or air in the system piping, with water under pressure held below the clapper of the valve. When a fire occurs, and the sprinkler activates, nitrogen or air pressure is relieved from the system piping, causing the valve to open and water to flow into the system pipe and any opened sprinklers.

Model FX: Standard Pressure Differential Valve

The Model FX differential valve is lightweight, compact, and requires no priming water, making it a snap to install and maintain. The external reset plunger is housed within a protective brass assembly which protects the plunger from damage during shipping, but more importantly, from accidentally resetting the valve prior to draining the system.

The model FX valve is fully assembled and rigorously tested at Reliable’s Liberty, South Carolina manufacturing facility. It is available pre-trimmed, including optional butterfly control valve and/or accelerator. Alarm and high/low air pressure switches are included with pre-trimmed FX valves. The single FX valve assembly makes it easy to specify, order and install, which saves valuable time for designers, purchasing managers, and fitters. The Model FX is available in 2” (50 mm) through 6” and 165 mm sizes, with Groove/Groove, Flange/Groove, and Flange/Flange end connections.

Model DDX-LP: Low Pressure Mechanical Valve

DDX-LP without optional accelerator

The DDX-LP low pressure mechanical valve can improve water transit times following the operation of the valve, and in some cases, eliminates the need for a quick opening device. Crafted from stainless steel, the clapper, seat, and push rod assembly provide protection against corrosion. Resetting the clapper of the Model DDX Valve is easily accomplished using the external reset knob.

The Model DDX-LP is a mechanical dry pipe valve that utilizes a series of devices to latch the clapper in the closed position with air or nitrogen pressure and without using the clapper surface areas to provide a differential. Reliable has manufactured mechanical dry pipe valves for more than 25 years.


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