Water Flow

Differences in Firefighting Valves: Siamese, Gated Wye, Water Thief

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Date November 03, 2023
Date November 03, 2023
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On the fire ground, firefighters use a lot of different equipment to move and control water. One vital piece of their water flow equipment is the different types of valves they use. If you’ve heard firefighters talk about a siamese, gated wye, manifold, or water thief, you might have wondered what they are and what the differences are. Let’s clear it up!  

What is a Siamese Valve? 

A siamese valve placed below a hydrant under monitor 

A siamese valve allows firefighters to combine multiple water sources into a single output. There are two or more inlets and a single outlet for distributing water. This allows firefighters to supply large amounts of water to a single source. 

The siamese may or may not have valves at each inlet. Valves at each inlet give the firefighter greater control over the water flow during use but may not be needed for the scenarios they encounter. Inside of the siamese valve there may also be a clapper which can automatically adjust water flow based on whether one or multiple sources are connected. 

Firefighters might use a siamese valve to supply water to an aerial apparatus, a pumper, or a high-volume ground monitor. 

What is a Gated Wye?