Valve FAQs

A fusion bonded epoxy, abbreviated to FBE, is a powder based protective coating system that prevents corrosion.  It is applied by spraying the dry powder epoxy onto a pre-heated surface, causing the powder to melt and adhere on contact.

A product carrying the WRAS approved logo has undergone independent testing by the Water Regulations Advisory Scheme, ensuring functional performance and that materials do not have a detrimental impact on the media quality.

Products that features WRAS listed components have not undergone this same testing, but feature a non-metallic component that individually carries approval for potable water usage.

The following T-T Flow valves carry WRAS approval:
• Aquavault resilient gate valves
• Swing check valves
• Aquabrake air valves
• Butterfly valves
• Pressure reducing valves
• Equilibrium float valves
• Twin plate check valve
• Brass gate valve

View the range here.

When you install a valve it's best to put it at least five pipe diameters away from anything that might make the flow of fluid in the pipe turbulent, like an elbow or a pump - this supports the valve's operations and prevent damage occuring from unstable flow.

Also consider how the valve will be accessed for future maintenance and the direction of flow in the system - some valves are unidirectional (will only work in one direction).

Our valves are coated in a durable fusion bonded epoxy coating, the colour is RAL5005.

Yes, the flange drilling of the valve (the size and shape of the holes on the valve flanges) can be different from the valve's pressure rating (maximum pressure that the valve can handle, marked on the body).

This means that the valve can be connected to pipes or equipment that have flange drillings of a different size or pressure rating, as long as the pressure rating of the valve body is not exceeded.

T-T Flow's valves are designed for clean/potable water or wastewater applications, with a maximum media temperature of 70°C and a maximum velocity of 3 m/s.

For valves with specifications outside of these parameters, T-T can design and manufacture a bespoke product to perfectly match the requirements of your application. Find details about our custom valve capabilities and solutions here.

To discuss your needs with a member of the team, please call +44 (0)1630 647200, email response@ttpumps.com or complete an online enquiry form.

Safety guards can be installed on both sides of a swing check valve to provide protection from moving parts in the valve.

Basic hand tools will be required - be sure to relieve pipeline pressure and isolate the flow before starting any work to prevent accidents or injury. Safety guards can help to prevent accidents, but proper safety procedures and precautions must always be taken.

For expert technical and mechanical advice, contact T-T Flow on +44 (0)1630 647200, email response@ttpumps.com or complete our online valves enquiry form.

Each individual valve at T-T is subjected to a hydrostatic pressure test as it leaves the production line. The body is tested to 1.5 x PN and seat to 1.1 x PN to guarantee the valve will perform safely and to its expected standard.

A valve interlock is a mechanical lock that only allows access to valve controls in the order that they are designed to be operated in. This prevents incidents or damage from occuring due to incorrect operation.

To operate the valves in sequence, the operator must insert a key into the first lock, unlocking the first valve. Once the first valve is opened, a key is released and can be used to unlock the next valve. This process continues until all valves in the sequence have been opened in the correct order.

A valve operating element is a mechanism that transfers torque to the valve, this could be a handwheel, lever, extension spindle, gearbox/actuator or interlock. These options are interchangeable across the T-T Flow range but may not fit valves from other manufacturers.

Handwheels are wheels attached to the valve's stem, allowing for manual operation via wheel rotation. They are usually designed for operating and adjusting smaller valves that do not require fine control or rapid opening/closing.

Levers use manual, linear or rotational force to operate the valve, ideal for larger valves, those requiring fast opening/closing and those that require a large force than a handwheel can provide.

Extension spindles extend the length of the valve stem to allow for the operation of valves in deep, confined or otherwise difficult-to-access locations.

Gearboxes (also known as actuators) provide automated valve opening, closing and adjusting via manual or motor-driven input. Similarly to extension spindles, gearboxes can provide operators with a greater degree of safety by enabling remote operation.

T-T Flow fabricates operation equipment in a variety of materials to match site-specific requirements at our HQ in Cheshire, including remote operators that negate the need for operators to enter into hazardous areas such as confined or below ground spaces.

Extension spindles can be provided as a one-piece sectional or complete unit, extending the length of a valve stem so that it can be operated from a safe location.

Gearboxes can be operated either manually or motor driven, allowing for automatic or manual operation from a low-risk location.

Headstocks, also known as pedestals, are fabricated in complementing materials and can be thrust or non-thrust taking - providing a safe and stable foundation for operating equipment to be installed upon.

PN (Pressure Nominal) is an alphanumerical, standardised rating system for identifying the pressure ratings of various components in a pipe system, including valves. PN roughly equates to bar, meaning a PN 16 valves would be rated to 16 bar.

This helps to ensure that components are compatible with each other and that the overall system is designed to handle the expected pressure conditions.

All check valves are designed to prevent pipeline backflow and prevent water contamination, equipment damage and flooding; there are different models that are designed for optimal performance in varying applications:

• Spring check valve - uses a spring-loaded disc that sits on a seat in the valve body and is held in place by a spring. Pressure from fluid flow in one direction pushes the disc away from the seat and allows fluid to pass. When the flow stops, the spring forces the disc back onto the seat.

• Swing check valve - uses a swinging disc that is pushed open by fluid flow in one direction. When the flow stops or reverses the weight of the disc swings it back into a closed position.

• Recoil check valve - Similar to a swing check valve, however the recoil valve has an inclined seat and body profile to reduce the damaging effects of water slam.

• Double hinge flap valve - simple valves featuring a flap attached with two hinges that allows flow in one direction and closes when flow stops or reverses.

• Ball break valve -  a self-acting valve that uses a ball to prevent backflow.  As the flow subsides the ball falls back into the valve seat, creating a seal and stopping any media from passing in the wrong direction.

• Twin plate check valve - two half-circle shaped plates are hinged and located inside the valve body, the plates swing open to allow flow in one direction, swinging shut if flow reverses.

A spring check valve features an axially guided sprung loaded disc to prevent reverse flow. Swing check valves offer an obstacle-free passage and suitable for clean and wastewater applications.  Spring check valves are only suitable for clean media’s due to the disc in the flow path.

Swing check valves are generally installed horizontally, but they can be installed vertically depending on the required set-up. Contact our experts for more information.

The maximum working pressure is 16 Bar.

Both valves are suitable for wastewater, and the choice will depend on the final system design and usage. The ball check valve is self-cleaning by design, although generally rated to lower working pressures.

Wedge gate valves are designed for isolation duty, left in either fully open or fully closed positions.

Using a gate valve to regulate flow will likely cause damage to the seats and/or wedge. Other valve types are more suited to flow regulation, such as our range of control valves.

T-T's swing check valves work to a maximum operating pressure of 16 bar.

Knife gate valves are suited to isolating fluid networks with higher concentrations of suspended solids such as wastewater and slurries.

A multiturn gate valve is designed to isolate the flow but means of a wedge that travels through the media.  When fully open a gate valve offers an unobstructed clean bore.  A quarter turn butterfly valve is designed to isolate or regulate the flow by means of a rotating disc in the flow path.  As such the butterfly valves are designed for clean medias.

The main difference between Non-Rising Stem (NRS) and Outside Screw and Yoke (OS&Y) gate valves is how the stem moves to operate the valve.

• NRS gate valves - the stem does not rise or extend above the valve body when operating, instead rotating to move the gate up/down inside the valve body while the stem remains in full contact with the media.
• OS&Y gate valves - the stem rises/extends to move in/out of the valve body when operating, this raises or lowers the gate inside of the valve body.

• Cast iron is an alloy containing 96%-98% iron, 2%-4% carbon, and small amounts of silicone - it can withstand high temperatures and pressure ratings but has no flexibility.
• Ductile iron is a created by the addition of magnesium alloy to molten iron, resulting in an iron that has improved strength, corrosion resistance and flexibility.

T-T offer gate valves are designed to BS5163/EN1074 for either water or wastewater duties up to 70C and maximum velocity of 3m/s.  Resilient gate valves are suited to clean and neutral fluids, while metal seat gate valves are suited to sewage and wastewater duties.   For duties beyond these constraints please contact us. 

Gate valves are not recommended for use at the end of a pipeline (end of line duty) because they are not designed to handle the higher pressure and flow conditions that can occur at the end of a pipeline.

Suitability rated blanking flanges are recommended - a type of flange that is used to block off and prevent any flow through the end of a pipeline.

A range of gate valve operating elements are available, ranging from a manual handwheel or stem cap that allows for remote operation via a T-key or extension spindle.

For automatic operation, intelligent actuators can be fitted.

Air Valves are valves that intake and release gas (de-aerate) from fluid management systems to protect the equipment from accumulated air pockets that can cause damage through pressure surges or vacuums.

Air can enter into fluid management systems in several ways:

• Naturally dissolved from water and waste fluids.

• During routine maintenance.

• Introduced during the initial installation.

• Drawn into the system through other equipment (e.g. turbulence from pumps).

If left unmanaged the flow-rate of fluid through the pipes becomes unreliable and structural damage can occur, leading to increased running costs due to operational inefficiencies and extra maintenance needs.

Air valves come in three main design configurations:

• Single small orifice air valve (single function/air release valve) - releases gas that accumulates while operating.
• Single large orifice air valve (two function/air vacuum valve) - releases and intakes gas during the system's draining and fluid pressurising (charging) phases.
• Double orifice air valve (three function/combination air valve) - has a small and large opening for different rates of gas intake and release.

Air valve positioning can affect the overall reliability and efficiency of the fluid management system.

• Single-function air valves are most effective at system high points for the release of accumulated air.
• Two-function air valves are ideal at system low points for the release of air pockets as well as the intake of air if fluid pressure drops, as this could affect the uphill flow of liquid.
• Double orifice air valves are best positioned where bulk inflow or outflow of gas is needed, with the added small orifice function maintaining system stability and efficiency.

Read our handy How-to: Choose & Position Air Valves guide in the Knowledge Hub for more information.

The needs and demands of the planned application will determine the ideal air valve design, size, construction materials and installation point.

For expert advice on choosing an air valve email response@ttflow.com, call +44 (0)1630 647200 or complete an online enquiry form.

• Knife gate valves - control the flow of fluids using a gate with a sharp edge that slides across the valve seat. When the valve is open, the gate retracts to allow fluid to pass through. When the valve is closed, the gate is across the valve seat to cut off flow. Knife gates are ideal for handling fibrous fluids, such as in slurry management systems.  
• Eccentric plug valves - a cylindrical valve body with a rotatable plug inside, the plug is offset from the centerline of the valve body, creating a straight-through passage when open and a seal against the valve seat when closed. Eccentric plug valves are designed for modulating the flow of various fluids, air and viscous media.
• Butterfly valves - use a disc-shaped element on a rotating shaft (central or off-set) that turns and opens to allow flow in one direction, turning back and shutting to stop flow in the opposite direction. Butterfly valves are best suited for clean water and oil-free airflow control.
• Penstock valves - use a gate that slides up and down between the valve body guides to stop and start the flow of liquid. Penstocks are commonly used in waterways, land drainage, hydropower and flood control applications, as well as being used in water, wastewater and sewage treatment plants.

Isolation valves are needed for any situations where flow needs stopping completely:

• Isolating part of a system for maintenance and repairs
• Emergency shutdowns
• Flow control

Selecting the optimal isolation valve model for your application will require consideration to:

• The media being handled - characteristics of the medium passing through the valve - such as whether it is a gas or liquid, if it contains solid, the viscosity of the medium - will determine which model of isolation valve you require to ensure effective pipeline isolation.
• Conditions of the application - the temperature, required flow rate and pressures that are reached during operation will decide the size and material composition of the valve to ensure it operated safely and reliably.
• Actuation method - applications that require rapid valve operation for emergency situations, or that have high pressure ratings, will require suitable control methods. Other factors include whether remote operation is needed to prevent operators from entering into hazardous areas (such as below ground or confined spaces).

Contact T-T Flow to discuss your valve requirements today and our team can advise you on the best equipment for your application.

Penstock valves are also known as sluice valves and use a sliding door that opens and closes to allow or inhibit the flow of water or sewerage. Penstocks can either be manually operated or by an automatic actuator such as a gearbox, with T-T Flow's model offering bi-directional sealing and stainless steel construction for versatility and durability.

A control valve is used to control the hydraulic characteristics of the media being pumped through the valve - they are able to reduce, sustain and increase system pressure as well as regulate the medium's flow rate.

Preventing a system from exceeding its designed pressure and flow rate protects the equipment from the damaging effects of water hammer and ensures consistent operating perameters for more reliable performance.

Equilibirum ball float valves are designed to regulate flow into tanks in order to maintain a consistent liquid level. The float attached to the valve rises and falls with the liquid in the tank, opening and closing the valve at pre-set levels to prevent overflow when levels are high and refill the tank when levels are low.

Some models of control valves allow for complete open/closed adjustment in a pipeline, however specifically designed isolation valves will operate the most efficiently.

Pressure reducing valves react to upstream pressure fluctuations in real time in order to maintain a consistent pressure level within a system. Preventing the system from exceeding its maximum pressure rating will protect it from damaging incidents such as water hammer.

Relief vavles are similar to pressure reducing valves in that they are designed to maintain a consistent system pressure, however relief valves do this by releasing excess air/liquid through a designated outlet in order to decrease pressure and prevent surges.

A knife gate valve is an isolation valve that allows or stops flow through a pipeline - they feature a sharp (knife) edge that cuts through suspended and fibrous solids or viscous fluids that would otherwise hinder the valve's sealing performance. 

Knife gate valves are designed to be installed between suitably pressure rated flanges, where they will offer many years of reliable isolation services.  To get the best from your knife gate valve it should complete at least one cycle annually and be visually inspected for media leaks.

Knife gate valves are available in different construction materials, sizes, pressure ratings, actuation methods and more.

To find the most effective knife gate valve model for your application, consider the characteristics of the media in the system, the pressure that will be generated by the flowing media and how often the knife gate valve will need to be opened and closed.

We offer manually and pneumatically actuated knife gate valves.

Our manual knife gate valves are opened and closed via turning a handwheel attached to a rising or non-rising stem, whereas our pneumatic knife gate valves have double-acting pneumatic cylinders that can be operated via a handwheel or remote control system. 

Knife gate valves are comprised of several main parts, the main components are:

• Body – The main outer structure that contains and supports the internal components.
• Plate – Also known as the gate or blade, the movable part of the valve that controls the flow of media.
• Seat (seal) – Where the gate makes contact to form a seal when the valve is closed, preventing the passage or leakage of any media.
• Stem – Connects the actuator (if present) to the plate, transmitting the force from the actuator to move the gate and open or closing the valve.
• Gland follower – A mechanism that compresses packing material around the stem, preventing leakage of fluid along the stem where it passes through the valve body.

T-T offers several popular valve designs in brass construction materials, such as:

• Gate valve.
• Swing check valve.
• Ball valve.
• Spring check valve.
• Spring check valve with strainer.

View the range here.

Brass valves lend themselves to small pipe diameters and can be used for a variety of purposes such as flow rate control and wastewater handling - they also a high level of corrosion resistance and a low level of operational friction, maximising the valves longevity.

A flange is a lip/rim/edge that extends past a piece of equipment (such as a valve inlet or outlet) and provides a strong base with which to safely attach other fittings, such as pipes and pumps.

Flanges can sit either externally or internally on the respective equipment depending on factors such as space restrictions. A fluid-tight seal is formed by placing gaskets between the two flanged surfaces to prevent leaks, secured by bolts and washers.

For more information on valve flagging, read our How-to Guide: Valve Flanges, Bolts & Tightening.

Jointing is the process of connecting two components to create a leak-tight seal - such as flanged joints used on pipe and valve ends. T-T Flow stocks a range of PN16 joint set kits, including galvanised bolts, nuts, washers, and and EPDM gasket for each f; and joint.

Male and female flanges are designed to be used together in order to ensure a secure connection between two fittings.

Male flange faces have raised sections and female flange faces have grooves/depressions that match, allowing for more precise sealing.

BS EN (British Standard, European Norm) 1092 is a specification of requirements held in Europe regardings flanges and joints for safe use in various industries.

BS EN 1092 covers pressure tolerances, temperature ratings, surfaces finishes, flange surface finishes and more - these standardisations aim to ensure consistence and quality in the design and manufacture of flanges, promoting safety and ease of use across different applications.

T-Keys are a type of manual valve operating equipment, named after its shape with a vertical stem and horizontal crossbar/handle.

T-Keys attach to a valve's stem (typically square or rectangular) and are generally used to open and close valves that are installed below ground. This remote operation prevents operators from having to enter into confined or otherwise hazardous spaces in order to adjust the valve.

T-Keys and extension spindles are similar in that they allow for remote operation of a valve without the need for entry into a hazardous location. However, extension spindles are an extension of a valve's handle or handwheel rather than the valve stem (which a T-Key connects to for remote operation).

Extension spindles are used to add length to a valve's operating component, allowing for remote operation that bypasses the need for operators to enter into dangerous areas in underground or confined spaces.

A gearbox is an actuation device (meaning it controls the position of the valve) that can be operated either manually by an operator or automatically via hydraulic, electric or motor energy sources.

Gearboxes are designed to amplify the input force for a greater output force, allowing operators to manually adjust large valves or those that operate under pressure more easily.

T-T Flow stocks gearbox models suitable for different uses and applications, view the range here.