Why are 2-way and 3-way Valves Necessary?

In this blog post, you’ll read:2-way and 3-way valves often have "A," "B," and "AB" markings on their intake and output ports. Different systems use these valves. You can use them for basic on/off tasks. You can also use them for more intricate tasks involving pumps and variable frequency drives (VFDs).
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2-way and 3-way valves often have “A,” “B,” and “AB” markings on their intake and output ports. Different systems use these valves. You can use them for basic on/off tasks. You can also use them for more intricate tasks involving pumps and variable frequency drives (VFDs).

How Does a 2-Way Valve Work?

Imagine a valve with an adjustable stem. The valve opens when you raise the stem and closes when you lower it. The flow usually goes straight through, often to a coil in an air-handling unit.

Types of Control for 2-Way Valves

These valves can be just on/off, or they can help control the flow.

Normally Open or Normally Closed?

In the world of 2-way valves, you’ll often hear “NO” for Normally Open and “NC” for Normally Closed. These terms tell you the valve’s default state when there’s no power. For example, in heating systems, valves are often set to fail normally open to prevent coils from freezing. Want to know more about control signals?

isolation ball valve
Isolation ball valve 2-way

Different control signals, from hauling off to modulating to pulse width modulation

Pulse Width Modulation (PWM)

Pulse width modulation (PWM) is a powerful digital technique that controls analog circuits through microprocessors’ digital outputs. It finds extensive measurement, communications, power control, and conversion applications.

Analog Circuits

Analog signals have continuously varying values with infinite resolution in both time and magnitude. They are distinct from digital signals, which have finite predetermined values. For instance, a volume knob on a car radio controls analog circuits, where the output is linearly proportional to the input.

Digital Control

Digital control of analog circuits offers cost and power savings. Microcontrollers and DSPs often include PWM controllers, reducing power consumption and costs. Digital control eliminates drift, making it ideal for precise applications.

PWM in a Nutshell

PWM encodes analog signal levels digitally. High-resolution counters modulate the duty cycle of a square wave to encode a specific analog signal level. The PWM signal remains digital as it switches the DC supply on and off in cycles. PWM can encode any analog value.

Example 1: Varying Duty Cycles

PWM signals with different duty cycles encode analog values. A 10% duty cycle means 10% of the signal strength, and a 90% duty cycle means 90%.

Example 2: Practical Application

A simple circuit driven by PWM involves powering an incandescent light bulb with a 9V battery. Adjusting the duty cycle controls the effective voltage applied to the bulb, affecting its brightness.

Modulation Frequencies

The modulating frequency of PWM must be sufficiently high for loads to respond effectively. Expected frequencies range from 1kHz to 200kHz.

PWM Controllers

Many microcontrollers include PWM controllers that allow users to set the period, on-time, and direction of PWM output. Enabling the PWM controller initiates the modulation.

  •  Digital vs. Analog:

PWM keeps the signal digital, minimizing noise effects and simplifying communication.

  • Noise Immunity: 

PWM enhances noise immunity, allowing more extended communication channels.

  • Applications: 

Various systems use PWM, including brake control, to offer precise pressure control for optimal performance.

What is a 3-Way Valve?

A 3-way valve has three ports: “A,” “B,” and “AB.” Port “AB” can connect to either port “A” or “B.” These valves usually appear in systems where the flow is constant and can be either mixing or diverting valves.

3 way angle valve
3-way angle valve

Mixing vs. Diverting in 3-Way Valves

A mixing valve has two inputs from the supply side and one output to the return side. It blends the two inputs before sending it out. On the other hand, a diverting valve has one input and two outputs. It channels the flow to one of the two return pipes.

What is Diverting Valves:

Diverting valves, another type of 3-way valve, redirect the fluid flow between multiple paths.

Diverting valves guide fluid down one path while blocking the other, unlike mixing valves that blend two streams.

A diverting valve, often known as a “three-way valve,” is an essential component of any HVAC system. These valves allow fluid distribution from the same source to two separate exits.

How Does it Work?

Anyone may utilize a diverting valve; expertise or training are not prerequisites. The provided valve body has one intake and two different exits. The valve’s internal mechanism can change to discharge fluid through either port singly or together. This function allows you to control the airflow and temperature in a room.

3 Way Shower Diverter Valve works
3 Way Shower Diverter Valve works

Applications in HVAC Systems

Diverting valves serve several functions in HVAC systems, including:

Temperature Control:

Hydronic heating systems use diverting valves to mix hot and cold water to reach the desired supply temperature. This maintains a steady and comfortable temperature inside.


In multi-zone HVAC systems, valves control the flow of conditioned water or air to specific areas in a building. This zoning capability may help save energy and accommodate people’s unique preferences for indoor climates.

Chilled Beams:

A common way to control chilled water flow in a business HVAC system is diverting valves.

Energy Efficiency:

Using a diverting valve to control the flow of hot and cold water may increase efficiency and cut costs.

Zonal Comfort:

They enable precise temperature control in different zones, ensuring occupants are comfortable throughout the building.

System Flexibility: 

Diverting valves provide flexibility in system design, making it easier to adapt to changing requirements or expansions.


Suitable diverting valves last a long time and are reliable, which helps HVAC systems work well.

Where to Install 3-Way Valves?

If the valve is in the supply, we use a diverting valve. Suppose you use a mixing valve in the return. Mixing valves is usually cheaper, so placing them in the return is a good idea.


Practical Examples of Valve Types

You might use a diverting valve in a fan coil unit. You might find mixing valves on the return side, passing water through a coil or bypassing it.

In HVAC, controlling air and fluid flow is essential for keeping indoor environments comfortable. One essential component that plays a significant role in this process is the diverting valve.

Understanding 2-Way and 3-Way Valves in HVAC

In HVAC (Heating, Ventilation, and Air Conditioning), precise fluid flow control is paramount for maintaining optimal indoor environments. Two valves instrumental in achieving this control are 2-way and 3-way valves.

1. 2-Way Valves

Effortlessly Regulating Flow:

2-way valves, or 2-port valves, are fundamental components in HVAC systems. They have two openings: one for inlet and the other for outlet. A 2-way valve controls fluid flow, like water or refrigerant, in a system.

maintains a constant flow rate
maintains a constant flow rate

Versatile Applications:

Several uses involving temperature control exist for these valves. Such valves regulate the circulation of fluids like hot water in hydronic heating systems and refrigerants in air conditioning systems. Their adaptability makes them essential for maintaining an ideal environment and maximizing the system’s efficiency.

Zonal Comfort:

Use a three-way valve instead of a two-way one for better fluid flow control. There is one intake and two outputs on these valves. HVAC systems commonly employ them to regulate temperatures and redirect fluids.

Fantastic Hotspots:

Multi-zone air conditioning and heating systems commonly use three-way valves. Such a system can control temperatures in different building parts separately. Each zone can have its temperature control for hot and cold air or water through a three-way valve.

Choosing and Using the Right Valves

The needs of your HVAC system will determine whether you need 2-way or 3-way valves. While two-way valves are enough for many uses, three-way valves provide more control over temperature and zoning.

Key Takeaways:

 Two-way valves are essential in controlling fluid flow in climate control systems. Three-way valves are beneficial in zoned HVAC systems for managing individual room temperatures. Your HVAC setup will require different valves, depending on the details.

If you want to know more about HVAC systems and 2-way/3-way valves, you’re in the right place! We extensively investigate how these factors affect a building’s thermal comfort and energy efficiency.


Versatile 3-Way Design

Typical applications

The type of valve you need for an application depends on the flow, the degree of control, shut-off, and pressure drops over the valve. Such as

1.   Controlling a single-acting cylinder

2.   Controlling a double-acting cylinder

Features and Benefits

  • Temperature adjustment tool in the valve cap for easier maintenance
  • You can easily install the portable adapter in 2-tap setups. A 4-in-1 fitting attaches to it. The fitting connects to a cold tap.
  • Works in more extensive systems with higher pressure differences between hot and cold water supplies, surpassing the industry standard.
  • Features Viton seals instead of EPDM to improve performance at higher temperatures significantly
  • Suitable for shower, bath, basin, and bidet hot water applications
  • Compatible with copper pipe only

Enhanced Actuation Speed and Control

Our valve integrates advanced technology to elevate actuation speed and enhance control, reducing response times for precise pneumatic circuit control. Please note that this valve is explicitly designed for AC voltage and does not function with DC coils.

Durability and Robust Construction

3-way and 2-way valves have a reputation for their durability and robust construction, which makes them reliable in various industrial settings. They use suitable materials to make them so they can handle harsh conditions and last a long time with little upkeep.

Wide Industrial Applicability

Many industries use these valves, such as chemical, petrochemical, HVAC, and pharmaceutical manufacturing. They can handle different fluids and control flow and direction, making them essential for fluid control in various sectors.

 Quality Assurance

We rigorously adhere to strict ISO9001 standards throughout manufacturing to ensure the highest quality. The valve’s thoughtful design seamlessly integrates into existing manifold setups, aligning with standard industry sizes. This positions it as an outstanding upgrade for various applications, delivering consistent and dependable performance.

Differentiating 2-way and 3-way valves

1.    Flow and Pressure Requirements

2.    Pressure and Actuation Response

3.    Integration with Hydraulic System Components

4.    Ergonomic Valve Configurations

5.    Maintenance and Replacement Requirements

6.    Temperature Resistance

Additional Valve Selection Considerations

1.    Ease of Maintenance

2.    Superior Seal Performance

3.    Nominal Pressure Drop During Flow

4.    Exceptional Actuation Response

5.    Convenient On-Line Procurement

6.    Manual Override

Predictable Availability and Serviceability

3 way valve works
3 way valve works

Three 2-Way Valve Description:

A three-way or three-way two-position valve is essential in fluid control systems. This valve regulates the flow of fluids in two directions within a pipeline. It features two ports, an inlet, and two outlets, allowing for versatile fluid movement control.

Different industries, like HVAC, pneumatic, and hydraulic machinery, use three 2-way valves. They are essential for controlling the flow of liquids or gases.

3-Way and 2-way Position Valve Diagram:

It is possible to use a graphic to explain the construction and operation of a three-way valve. The three primary parts are the inlet, the exhaust, and the internal mechanism. The valve can close one outlet while keeping the other open, as shown in the diagram. This switching action applies to various fluid circuits because mechanical or electrical input can trigger it.

Three 2-Way Valve Symbols:

In engineering and industrial schematics, we typically represent a three-way valve with a rectangle. This rectangle has three lines coming out of it. There are two outlet connectors and one intake plug included.

Depending on its construction, a valve can either be “normally open” or “normally closed,” and the icon depicts both states. Engineers and technicians may better regulate fluid flow thanks to quickly identifying three 2-way valves in system schematics.

Three 2-Way Valve Normally Open:

A “normally open” valve allows fluid to flow from the inlet to one of the outlets without any extra force. This setup is often employed when continuous fluid flow is critical, but no external control signals are available. The valve’s actuator or control mechanism briefly switches the flow from its typically open exit to the opposite outlet. For this reason, it is well-suited for uses where security and dependability are of fundamental importance.

2 Way Valve Operation

The two-way valve is the most frequent form of control valve. Mainly, it regulates the flow of fluids by letting some in and keeping others out. A two-way valve may be used with minimal effort.

electric two way valve body
electric two-way valve body

When the valve is open, fluid can flow freely through it. On the other hand, when the valve is closed, no liquid can flow through it. Applications where flow regulation is critical benefit from two-way valves’ on/off functionality.

On/Off Applications:

A two-way valve’s on/off design is handy when temporary flow regulation is needed. These valves may be found in most industrial settings because of the frequent requirement to regulate fluid flow.

They also have a use in climate control systems, where they help maintain a steady temperature by controlling the flow of water or other fluids. Two-way valves are used in various industries, including manufacturing, irrigation, and oil and gas.

Variable Flow Systems:

Two-way valves have more applications than simple on/off systems since they allow varying flow rates. In such arrangements, the flow rate is regulated by a valve that is neither entirely open nor closed. Changing the position of the valve allows for fine regulation of fluid flow to match individualized needs.

To maintain a comfortable temperature in a building, regulating the flow of chilled or heated water is necessary, making 2-way valves an essential component of climate control systems.

Chilled or Hot Water Applications:

In most cases, two-way valves are installed in systems that use cooled or heated water. These valves are a standard fixture in heating, ventilation, and air conditioning (HVAC) systems, regulating the flow of conditioned water. Changing the velocity of chilled water flow or the temperature of hot water will alter the cooling or heating impact accordingly. Two-way valves are often used in HVAC systems since they may be operated with cold or hot water.

3 Way Valve Operation

Connections Between Valves:

Three-way valves are more cost-effective than several two-way valves for applications that require diverting and mixing. These valves have three ports, allowing fluid to be routed in various directions.

Since a 3-way valve may be used independently, it streamlines the assembly process. Typical applications include temperature control, water treatment, and industrial operations requiring precise flow regulation.

Mixing Valves:

A three-way mixing valve regulates the fluid’s temperature or concentration. These valves are typically installed in homes with domestic hot water systems to control the water temperature coming to fixtures like showers and sinks. Mixing valves adjust the hot and cold water ratio, allowing for consistent comfort with little energy cost.

water shower thermostatic valve
water shower thermostatic valve

Diverting Valves:

This type of valve is frequently used in industrial settings and home plumbing to regulate the flow of fluids, such as water in an irrigation system or various media in a chemical processing plant.

Internal Linking:

Connecting a 3-way valve’s ports internally is what’s meant by “internal linking.” Depending on their internal construction, these valves may mix or divert them. The valve’s internal components may be adjusted to direct or mix the flow of a fluid precisely.

Internal linking is essential in ensuring proper operation and achieving the desired outcome in various applications where 3-way valves are employed.


In conclusion, choosing between 2-way and 3-way valves is essential for fluid control systems. 2-way valves are versatile, serving well in on/off and variable flow scenarios. On the other hand, 3-way valves offer advanced fluid control, whether it’s diverting flow or mixing.

For precise temperature regulation, mixing valves are invaluable, while diverting valves efficiently manage flow redirection. The decision between these 3-way and 2-way valve options depends on specific application requirements, with 3-way valves granting enhanced control, particularly in HVAC and industrial settings. Have you got more questions?


What are a two-way valve and a three-way valve?

A two-way valve has two ports and controls fluid flow by allowing or blocking it, while a three-way valve has three ports and directs fluid flow between two different paths.

What is the difference between a 2-piece- and 3-piece valves?

A 2-piece valve is constructed from two parts bolted together, whereas a 3-piece valve consists of three separate components that can be disassembled for easier maintenance and access to internal parts.

What is the difference between 2-port and 3-port motorized valves?

A 2-port motorized valve controls fluid flow in a single direction with two ports. In comparison, a 3-port motorized valve offers multiple configurations to control fluid flow between any two of its three ports.

What is a 3-way valve?

A 3-way valve features three ports and is used to divert or mix fluid flow between two different paths, providing flexibility in fluid distribution in various industrial applications.

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