What Is a Hot Tap? How Live Pipe Connections Work

WHAT IS A HOT TAP?

A hot tap is a controlled method of creating a new connection on an existing piping system while the line remains in service. Instead of shutting down and draining the entire system, specialized hot tapping equipment is used to install a branch connection and cut an opening into the live pipe under controlled conditions.

Hot tapping is commonly considered when a facility needs to add a new branch, valve, bypass, instrument connection, equipment connection, or future tie-in point while maintaining operation of the existing piping system.

The key advantage is continuity. When the piping condition, operating parameters, connection design, and field conditions are suitable for live work, a hot tap can reduce the amount of shutdown-related work required for a system modification.

HOW DOES A HOT TAP WORK?

Every hot tap starts with planning. Before equipment is installed, the existing piping system must be reviewed to determine whether the proposed live connection can be carried out safely and effectively.

Typical information reviewed before a hot tap includes:

• Pipe size
• Pipe material
• Wall thickness
• Operating pressure
• Operating temperature
• Line contents
• Pipe condition
• Branch connection size
• Fitting type
• Valve requirements
• Available access and clearance
• Tapping-machine capacity
• Connection orientation
• Site operating requirements

Once the connection has been reviewed, the branch fitting is installed on the existing pipe. The required isolation valve is then installed on the new branch.

The hot tapping machine is mounted to the valve and aligned with the branch connection. The machine contains the cutter and pilot assembly used to create the opening in the live pipe.

After the setup has been checked, the valve is opened and the cutter is advanced through the branch fitting and into the existing pipe wall. The cutter removes a circular section of pipe while the system remains contained.

That removed section is known as the coupon.

After the cut is completed, the cutter and coupon are retracted back through the valve. The valve can then be closed, allowing the tapping machine to be removed while the active piping system remains contained.

The result is a new branch connection that can be used for future piping, valves, equipment, bypasses, instruments, or other system modifications.

WHAT IS COUPON CAPTURE?

Coupon capture is one of the most recognizable parts of a hot tapping operation.

When the cutter passes through the existing pipe wall, it removes a circular section of material. The tapping assembly is designed to retain this section so it can be removed with the cutter after the opening has been completed.

Verified coupon recovery helps confirm that the cut section has been successfully removed rather than left loose inside the piping system.

For this reason, coupon retention and recovery are an important part of hot tap planning and execution.

WHY USE A HOT TAP INSTEAD OF A FULL SHUTDOWN?

A conventional piping modification can involve much more than simply stopping flow.

Depending on the system, a shutdown may require:

• System isolation
• Drain-down
• Product transfer
• Temporary storage
• Lockout procedures
• Refill
• Air removal
• Water treatment adjustment
• Pressure restoration
• System balancing
• Restart
• Recommissioning
• Coordination with occupants, production, operations, or tenants

Those activities can add time, cost, scheduling complexity, and operational risk to a project.

When the existing piping and operating conditions are suitable for hot tapping, a live connection can reduce many of those shutdown-related requirements.

This can be especially valuable in facilities where heating, cooling, utilities, production systems, or other critical services need to remain available.

HOT TAP PLANNING AND ENGINEERING CONSIDERATIONS

Hot tapping is not simply a matter of drilling into a live pipe.

The success of the operation depends heavily on what happens before the cutter touches the pipe.

The existing system must be reviewed to determine whether the pipe, fitting, valve, equipment, and field conditions are compatible with the proposed live connection.

Pipe material is one important factor. Different piping materials behave differently during fitting installation, cutting, sealing, and field handling.

Wall thickness also matters because the connection design and cutting process depend on the physical condition and dimensions of the existing pipe.

Operating pressure and temperature are important because the hot tapping equipment, valve, fitting, seals, and field procedure must all be suitable for the system conditions.

The line contents must also be understood. Water, glycol, cooling water, heating water, nitrogen, and other services each introduce different planning considerations.

Access can become a major part of the job as well. Mechanical rooms, underground spaces, congested piping areas, tanks, and large-diameter systems can limit how equipment is positioned and supported.

For larger hot taps, equipment alignment and loading become increasingly important. The valve, tapping machine, cutter assembly, and branch components can create significant physical loads. The setup must be planned so the equipment can be installed and operated in a controlled manner.

HOT TAP EQUIPMENT

A typical hot tapping setup can include several major components.

Branch fitting:
The fitting creates the new connection point on the existing piping system.

Isolation valve:
The valve allows the branch to be opened for the tapping operation and then closed after the cutter has been withdrawn.

Hot tapping machine:
The tapping machine controls the cutter as it advances through and retracts from the live pipe.

Cutter and pilot assembly:
The cutter removes the required opening while the pilot assembly helps retain the coupon.

Adapters and connection hardware:
These components connect the tapping machine to the valve and branch arrangement.

The exact equipment configuration depends on the pipe size, branch size, system conditions, fitting design, and project requirements.

HOT TAP VS. LINE STOP

Hot tapping and line stopping are related live-system services, but they perform different functions.

A hot tap creates a new opening or branch connection on an active piping system.

A line stop creates a temporary isolation point inside an active line so a section of piping can be repaired, replaced, modified, or removed while the larger system remains in operation.

In some projects, hot tapping is used first to create the access points needed for a line stopping operation.

For example, a project may involve hot tapping the active pipe to install the line stop equipment, isolating a section of the system, completing the required repair or valve replacement, and then restoring normal operation.

That is why hot tapping and line stopping are often discussed together, even though they serve different purposes.

WHERE ARE HOT TAPS USED?

Hot tapping can be used across a wide range of mechanical, utility, and industrial piping applications.

Examples can include:

• Heating systems
• Cooling systems
• Chilled water systems
• District energy systems
• Water mains
• Utility piping
• Process piping
• Glycol systems
• Storage tanks
• Commercial mechanical systems
• Institutional facilities
• Industrial facilities

The suitability of hot tapping still depends on the specific system and project conditions. A live connection should be reviewed individually rather than treated as a one-size-fits-all solution.

LARGE-DIAMETER HOT TAPPING

As hot tap diameter increases, the physical setup becomes more demanding.

Larger valves, fittings, tapping machines, cutters, and support arrangements require more space and careful equipment positioning.

Alignment becomes especially important because the tapping machine must remain properly positioned through the entire cutting and withdrawal process.

WellFab has completed large-diameter hot tapping work, including a 24-inch live hot tap on an active pipeline.

On projects of this scale, the work plan must account for equipment setup, valve alignment, cutter control, coupon recovery, system monitoring, and safe removal of the tapping equipment after the connection is complete.

HOT TAPPING ON COOLING SYSTEMS

Cooling systems are one area where shutdown avoidance can provide significant value.

A conventional connection on an active cooling main may require draining the line, refilling the system, removing air, restoring operating conditions, and recommissioning the affected loop.

WellFab has completed two 8-inch live hot taps on active cooling mains at an MDE facility.

The connections were completed while the cooling system remained in operation, reducing the amount of shutdown-related work required to establish the new branch points.

HOT TAPPING A STORAGE TANK

Hot tapping can also be used for certain tank connections when the tank condition, product, design, and proposed connection are suitable for live work.

WellFab completed a 14-inch live hot tap on an active glycol storage tank.

That project required planning around the curved tank shell, wall condition, access limitations, cutting requirements, and protection of the glycol product.

Completing the connection live avoided tank drain-down, temporary storage, product transfer, and extended shutdown activities.

HOT TAPPING A NITROGEN LINE

Different system contents create different planning requirements.

WellFab has also completed a 3-inch turnkey hot tap on an active nitrogen line.

The scope included planning, material supply, branch welding, hot tapping, testing, inspection, and system reinstatement.

This type of project highlights the importance of reviewing the entire system and execution method, not just the branch size.

PVC HOT TAPPING

Not every hot tap is performed on metallic piping.

WellFab has also completed a 6-inch hot tap on an existing PVC piping system.

PVC requires a material-specific approach because branch preparation, cutting, sealing, connection support, and field handling differ from metallic piping.

This is another example of why the piping material should be confirmed during the early planning stage.

WHAT INFORMATION SHOULD BE PROVIDED FOR A HOT TAP REVIEW?

Providing accurate project information early helps determine the appropriate connection method and equipment.

Useful information can include:

• Existing pipe size
• Branch connection size
• Pipe material
• Wall thickness
• Operating pressure
• Operating temperature
• System contents
• Pipe condition
• Connection orientation
• Proposed fitting or valve requirements
• Available working space
• Photographs of the existing piping
• Drawings or sketches
• Shutdown limitations
• Site access requirements

The more complete the information, the easier it is to review the proposed connection and identify potential constraints before mobilization.

WHEN SHOULD A HOT TAP BE CONSIDERED?

A hot tap may be worth considering when a new connection is required and a full system shutdown would create significant operational disruption.

Typical reasons can include:

• Adding a new branch connection
• Supporting system expansion
• Installing new equipment
• Creating a future tie-in point
• Preparing for a bypass
• Supporting a line stopping operation
• Adding valves or instrumentation
• Modifying active mechanical infrastructure

However, not every pipeline or operating condition is suitable for hot tapping.

The existing piping condition, material, pressure, temperature, contents, access, fitting design, and proposed connection must all be reviewed before proceeding.

REAL HOT TAP PROJECTS

WellFab's hot tapping project experience includes a range of diameters, system types, materials, and field environments.

Examples include:

24-inch Hot Tap – Live Operation
A large-diameter live connection completed on an active pipeline without a full shutdown.

10-inch Hot Tap – Tonisco Valve Solution
A live branch connection completed using a Tonisco hot tapping valve system.

MDE – 8-inch Cooling Hot Taps
Two live hot taps completed on active cooling mains while maintaining system operation.

14-inch Live Hot Tap – Glycol Storage Tank
A live connection completed on an active glycol storage tank with planning around tank geometry, access, and product protection.

6-inch Hot Tap – New Connection Installation
A new branch connection created on an active pipeline using a Tonisco valve.

3-inch Hot Tap – Turnkey Nitrogen
A complete turnkey connection including material supply, welding, live tapping, testing, and reinstatement.

6-inch PVC Hot Tap
A new connection completed on an existing PVC piping system using a material-specific execution approach.

HOT TAPPING SUPPORT FROM WELLFAB

A successful hot tap starts long before the cutting operation.

The project should begin with a clear understanding of the existing piping system, operating conditions, connection requirements, access, equipment needs, and the operational reason for performing the work live.

WellFab supports hot tapping projects from initial review through field execution, including connection planning, fitting and valve requirements, equipment selection, tapping-machine setup, controlled cutting, coupon recovery, system monitoring, and final connection verification.

For hot tapping capabilities, operating ranges, equipment information, and additional project examples, visit WellFab's Hot Tapping Services page.