water in one direction only.

3way valves have three ports, labelled A, B, and AB. With three ports, the 3-way valve passes the water in two directions.

These are two criteria to determine if you need a 2way valve or a 3-way valve: water flow, and the type of valve operation you require.

Water Flow

Use a 2way valve in a system with a variable water flow that experiences changes in flow, pressure, and temperature. 2-way valves allow operators to run heating and cooling systems at variable flow rates, increasing process efficiencies, and lowering their operating costs.

The 3-way valve is used in a system with constant water flow.

Valve Operation

2way valves only have a simple On/Off operation. They can immediately stop fluid flow to a specific location and are essential components in many process safety systems.

3-way valves have two different operations: They can be used as mixing valves or diverting valves.

When used as a mixing valve, fluids of varying temperatures and pressures from ports A and B are mixed inside the valve body. The mixed fluid is transmitted out of port AB.

When used as a diverting valve, the fluid can either flow from AB to B and vice versa, or AB to A and vice versa. The 3-way valves have an L-shaped or T-shaped bore, which affect the circuit function (flow direction). This can be seen in Figure 3. As a result, various circuit functions can be achieved such as distributing or mixing flows.