What is a Ball Valve? How It Works and Types Explained
Ball valves are among the most widely used valves in UK water supply, industrial pipework, and liquid storage systems. Simple to operate, fast to actuate, and available in sizes from a fraction of an inch to several hundred millimetres, the ball valve is the standard choice for on-off flow control across an enormous range of applications. Yet despite how commonly ball valves are used, the differences between valve types, port configurations, and construction designs are poorly understood by many of the engineers, farmers, and facilities managers who specify them every day.
For anyone managing a water storage tank installation, whether for potable water, irrigation, slurry, trade effluent, or industrial process water, choosing the right valve for each connection is as important as choosing the right tank and liner kit. This guide covers everything you need to know: what a ball valve is, how it works, the main parts, the different types available, how ball valves compare to other common valve types, and how they are specified on UK water storage tank systems.
What is a Ball Valve?
A ball valve is a type of quarter-turn shut-off valve that uses a rotating ball with a hollow bore drilled through its centre to control the flow of liquid or gas through a pipeline. When the valve handle is turned ninety degrees, the ball rotates inside the valve housing so that the bore either aligns with the pipeline to allow flow or sits perpendicular to it to block flow completely.
The ball valve gets its name from the spherical closure element at its heart. Unlike a gate valve, which uses a sliding gate that moves linearly into the flow path, a ball valve controls fluid flow through rotation. This makes it one of the fastest and most reliable valves for on-off isolation, operable in a single quarter turn by hand or by actuator. Ball valves are suitable for use with water, gas, oil, chemicals, slurry, and a wide range of industrial fluids, and ball valves are commonly used across water supply networks, agricultural systems, industrial process plants, and liquid storage installations of every scale.
How Does a Ball Valve Work?
Understanding how a ball valve works starts with the hollow ball at its core. The ball sits inside the valve body, held in position by two seats, one on either side, that create a seal against the surface of the ball when it is in the closed position. A stem connects the ball to the handle or actuator on the outside of the valve housing.
When the valve is open, the ball can be rotated so that the hole in the ball runs in line with the pipe on both sides. Fluid flows freely through the valve with minimal restriction. When the valve handle is turned ninety degrees, the ball rotates so that the solid side of the sphere faces the flow path, blocking it completely. The valve is closed and flow stops entirely.
The critical operational characteristic of a ball valve is this: it moves from fully open to fully closed in a single quarter turn of the handle. This makes it extremely fast to operate and gives a clear visual indication of valve position at all times. When the handle is parallel to the pipe, the valve is open. When it sits perpendicular to the pipe, the valve is closed. There is no ambiguity about the position of the valve at any point in its operation, which makes it a practical and reliable choice for tank connections operated regularly by site personnel.
Ball valves are designed for fully open or fully closed operation. They are not suited to flow throttling or regulation. Using a ball valve in a partially open position causes erosion of the seats and ball surface over time and reduces the service life of the valve considerably. For applications requiring flow modulation, a butterfly valve or a dedicated control valve is the correct specification.
Parts of a Ball Valve
A ball valve consists of several key components, each of which affects how the valve performs in service.
The valve body is the outer shell that houses all internal components and connects to the pipeline at each end. Valve bodies are typically manufactured from stainless steel, brass, carbon steel, or PVC depending on the application and the liquid being controlled.
The ball is the spherical closure element with a bore drilled through its centre. Metal ball construction, typically stainless steel or brass, is standard for water supply and industrial applications. The diameter of the bore relative to the pipe determines whether the valve is full-port or reduced-port, covered in the types section below.
The seats are the sealing rings that contact the surface of the ball on either side and create a watertight seal when the valve is in the closed position. PTFE seats are the most common material for water and general industrial use.
The stem connects the ball to the handle or actuator outside the valve housing. When the valve handle is turned, the rotational movement transfers directly through the stem to the ball inside the valve body.
The handle is the external operator. On manually operated ball valves this is typically a lever. On larger or automated systems it may be replaced by a pneumatic actuator, hydraulic actuator, or electric motor drive.
The valve housing seals the stem from the outside environment and prevents leakage along the stem axis. The overall construction and material specification of the housing determines the pressure rating and service life of the valve in the installed condition.
Types of Ball Valve
Understanding the different types of ball valves matters because valve construction, port configuration, and actuation type directly affect which application each valve is suited to.
Full-Port vs Reduced-Port Ball Valves
The port configuration is one of the most important specifications for water storage tank applications. A full-port ball valve has a ball bore diameter equal to the internal diameter of the connected pipe. This means the valve has no obstruction to water flow when it is open, producing minimal pressure drop and allowing unrestricted flow through the valve opening.
A reduced-port ball valve has a bore smaller than the pipe diameter. This creates a slight restriction even when fully open, producing a small but measurable pressure drop and reduced flow rate. For high-volume tank outlets, irrigation distribution connections, and potable water supply lines, full-port ball valves are the correct specification. Reduced-port valves are suited to applications where the small restriction is acceptable and where cost is a priority.
Two-Piece vs Three-Piece Ball Valves
Two-piece ball valves have a body made from two sections that are permanently assembled. They are compact, cost-effective, and the most commonly used configuration for standard water supply and general industrial applications where routine disassembly is not required.
Three-piece ball valves have a body made from three sections: a central body housing the ball and seats, and two end caps that bolt to the pipeline connections. The central body can be removed entirely for inspection, seat replacement, or cleaning without disturbing the pipeline. Three-piece ball valves are the preferred choice for larger tank installations and industrial process lines where maintenance access and long service life matter most.
Floating Ball vs Trunnion Ball Valves
In a floating ball design, the ball is held in position by the two seats and is free to move slightly under line pressure. This movement presses the ball firmly against the downstream seat, creating a tight, reliable seal. Floating ball valves are the standard configuration for most water storage and supply applications up to moderate pressure and pipeline size.
In a trunnion ball design, the ball is supported by additional mechanical anchoring points above and below the ball as well as by the seats. This prevents the ball from moving under line pressure, reduces the operating torque required, and extends seat life. Trunnion ball valves are specified for larger valves and higher-pressure applications where the forces exerted on the seats in a floating ball design would cause accelerated wear.
Vented Ball Valves
A vented ball valve has a small hole drilled into the ball itself. When the valve is closed, this vent allows any pressure trapped in the valve body between the two seats to equalise, preventing pressure build-up that could force the valve to open or damage the seats over time. Vented ball valves are specified in applications where thermal expansion of trapped liquid, or pressure cycling in the pipeline, could otherwise create problems.
3-Way and 4-Way Ball Valves
A standard ball valve controls flow in a single direction through one flow path. A 3-way ball valve has three ports and a ball designed to direct flow between them in different configurations depending on handle position. This makes a 3-way ball valve useful for diverting flow between two outlets, mixing flow from two inlets into one, or isolating one branch while allowing flow through another. A 4-way ball valve has four ports and provides even more complex flow direction options for specialised process applications. These are used across water distribution systems where multiple simultaneous flow paths must be managed through a single valve body.
Manual, Pneumatic and Hydraulic Ball Valves
Manually operated ball valves are operated directly by hand via a lever handle and are the standard choice for most tank inlet and outlet connections operated infrequently or where automation is not required. Pneumatic ball valves use compressed air to actuate the quarter-turn movement, allowing remote or automated operation in larger installations. Hydraulic ball valves use hydraulic pressure for actuation and are used in applications where the valve must be operated frequently or remotely without manual intervention.
Ball Valve vs Other Valve Types
Ball valves are frequently compared to gate valves, butterfly valves, globe valves, and plug valves. Each type serves a different purpose and the right choice depends on the application, the liquid being controlled, and how often the valve will be operated.
Compared to a gate valve, a ball valve opens and closes in a single quarter turn rather than through multiple rotations of a handwheel. Ball valves are faster to operate and better suited to connections requiring frequent use. Gate valves are generally preferred for larger bore isolation where operating frequency is low and full-bore fluid flow with absolutely no internal restriction is the priority. Ball valves are the more practical choice for smaller and medium bore connections on tank systems that are opened and closed regularly.
Compared to a butterfly valve, a ball valve provides a tighter seal in the closed position and has no disc remaining in the flow path when fully open. Butterfly valves are lighter, more compact, and more cost-effective for large-diameter applications, but the disc creates a permanent small restriction and they are more susceptible to wear from particulate matter in the flow.
Globe valves and plug valves use different closure mechanisms and are generally less suited to simple on-off water isolation than ball valves. Globe valves are better specified for flow regulation and throttling. Plug valves are used in applications handling slurry or solids-laden liquids where the seats inside a ball valve would wear quickly under abrasive conditions.
Ball Valves in UK Water Storage Tank Applications
Gate valves, ball valves, and butterfly valves are all available as standard fittings across our accessories range for corrugated steel water storage tanks, in inlet and outlet sizes from 2 inches to 12 inches, specified to match the tank, the liner, and the application. Ball valves are the most commonly specified fitting for smaller bore connections on tank installations where the valve will be operated regularly in day-to-day water management.
On a Butek Tanks corrugated steel water storage tank, ball valves are typically specified on secondary outlet connections, draw-off points, sampling connections, and smaller diameter inlets where fast, reliable on-off isolation is needed. Their quarter-turn operation makes them practical for operators who need to open and close connections quickly, and their compact form makes them easy to integrate into tight pipework layouts around the tank base.
For tanks storing potable water, all ball valves must comply with the Water Supply (Water Fittings) Regulations 1999 and carry WRAS approval, confirming that the materials used will not contaminate the stored drinking water. Stainless steel and brass ball valves with PTFE seats are the standard specification for WRAS-compliant potable water connections on corrugated steel water tanks.
For tanks storing trade effluent, slurry, digestate, or industrial process liquids, the valve material specification must be matched to the chemical composition of the stored liquid. Valves on slurry tanks must resist ammoniacal nitrogen and the abrasive nature of the stored material. Valves on trade effluent or chemical storage tanks must be specified for compatibility with the specific effluent type. Our team specifies valves as part of the overall tank design, ensuring every fitting is matched to the liquid and the application alongside the correct liner kit and roof kit selection.
Full professional installation services are available for every tank configuration, with valve and pipework installation carried out as part of a complete commissioning package.
Frequently Asked Questions About Ball Valves
What is a ball valve used for?
A ball valve is used to start or stop the flow of liquid or gas through a pipeline. It is a quarter-turn shut-off valve suited to water supply, industrial pipework, agricultural systems, and liquid storage tank connections where fast, reliable on-off isolation is required. Ball valves are not suited to flow throttling or regulation.
What is the difference between a ball valve and a gate valve?
A ball valve uses a rotating ball with a hollow bore and opens or closes in a single quarter turn of the handle. A gate valve uses a sliding gate that moves linearly and requires multiple turns of a handwheel to open or close fully. Ball valves are faster to operate and better suited to frequently used connections. Gate valves are more reliable for large bore isolation where operating frequency is low and completely unrestricted full-bore flow is the priority.
What is a full-port ball valve?
A full-port ball valve has a bore diameter equal to the internal diameter of the connected pipe. This means the valve produces no restriction and no pressure drop when fully open, making it the correct specification for high-volume water supply connections, tank outlets, and irrigation distribution lines where flow rate matters.
Can a ball valve be used for flow control?
No. Ball valves are designed for fully open or fully closed operation only. Using a ball valve in a partially open position causes erosion of the ball and seats, vibration, and accelerated wear. For applications requiring flow modulation or throttling, a butterfly valve or dedicated control valve should be specified instead.
What materials are ball valves made from?
Ball valves are available in stainless steel, brass, carbon steel, PVC, and other materials depending on the application. For UK potable water applications, stainless steel and brass ball valves with PTFE seats and WRAS approval are the standard specification. For industrial and chemical storage applications, the material must be selected for compatibility with the specific liquid being controlled.
What is a 3-way ball valve?
A 3-way ball valve has three ports and a specially designed ball that can direct flow between them in different configurations. It is used to divert flow between two outlets, mix flow from two inlets into one, or isolate one branch while allowing flow through another, making it useful in more complex pipework layouts than a standard two-port ball valve.
Need a Bespoke Water Storage Tank with the Right Valve Specification? Butek Tanks Can Help
Whether you are specifying a new potable water storage system, an agricultural slurry tank, a trade effluent containment solution, or a large-scale industrial process water installation, Butek Tanks supplies gate, ball, and butterfly valves in all sizes and materials as part of a complete tank solution alongside our liner kits and roof kits. As a specialist division of Butyl Products Ltd, we design, manufacture, and install corrugated steel storage systems for water, wastewater, effluent, slurry, and a wide range of liquid storage applications across the UK and internationally. Our solutions are ISO 9001:2015 certified, CE marked, and deployable globally.
Get in touch today. Call us on +44 (0)1277 653 281 or email enquiries@butektanks.co.uk, or visit our contact page to submit your project requirements. Our team will respond promptly to discuss your needs.