What Is a T-Splice?

Mary McMahon
Mary McMahon

A T-splice is an electrical connection where a branch wire is brought to the middle of a main wire to connect it into the system. This is also known as a tap or T-tap splice, depending on regional preferences for electrical terminology. Such connections can be used with electrical wiring of a variety of types, as well as cable, telephone, and other kinds of wiring that uses electrical signaling. Each splice needs careful inspection to confirm that it is installed properly and safely, and will not fail with future use.


One method for wiring a T-splice is manually. A technician can carefully strip some of the insulation from the main wire and the end of the branch wire, and twist the branch wire around the main. If the twists are snug and secure to wrap the wire tightly, it shouldn't give way under pressure. Once the connection is complete, the technician can wrap it with electrical tape to provide insulation and security, and may add weatherproof taping or other insulation options, depending on the setting.

Another option is a snap-in connector. A T-splice connector snaps over the main wire, biting in to create a connection between the wire and a small connector inside the device. The technician can attach the branch wire to this connector, and the connection will be securely sealed inside the case. Some are lined with gel and other materials to provide additional insulation and limit incursion from the elements. T-splices can be weak points in wiring, and it is important to protect them from corrosion and other potential sources of damage.

There are a number of reasons why a technician may need a T-splice. In street lighting, for example, workers can add new lights by splicing onto a line, rather than running fresh wiring. Since they are all on the same circuit and need to activate at dusk to provide safety lighting, splicing allows the new light to run at the same time as the other lights on the same line. T-splices can also provide a method for running secondary lines, as seen in home telephone wiring systems.

This is one among a number of types of electrical splices. People in training for careers in this field learn about the variety of options available and the best choices for various applications. These kinds of connections need to be installed with care, as errors can create safety problems. Loose wires may generate shorts that could damage the wiring and the system, for example. An improperly installed T-splice can also be a problem with a communications line, as it might cause interference that leads to crackling, buzzing, or poor image quality.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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