LPG Pigtail

The propane tank and regulator connection is commonly called the pigtail or hogtail. The pigtail connects to the service valve of the propane tank and the inlet connection of the regulator. This connection is relatively small in diameter, which initially restricts gas flow from the tank to the regulator. Pigtails must be replaced when the regulator is replaced.

 Propane Regulators and Flexible Connectors

The NFPA defines the tank and regulator's regulator connection (pigtail) as a flexible connector. Flexible connectors must be 36 inches or less, meaning the regulator will be installed no more than 36 inches away from the service valve. The primary reason for this 36-inch maximum length is protection against tank pressure being delivered to the downstream piping in the event of a leak. If there is a leak in the system, the regulator acts as a protective device and will not allow the tank's full LP Gas vapor pressure to reach downstream. Pigtails also function as a protective measure against the movement in the gas line. They are "flexible" and will absorb the shock of sudden movement or jarring of the gas service line if accidentally bumped or moved out of place. Without the flexible regulator connection, the piping would be rigid and more susceptible to leaks forming if the piping, tank, or service line moves, either gradually or suddenly. See Figure 1 below

Figure 1

Propane regulator connections are available in varying lengths and bends. Although many of the pigtails installed are straight, the technician bends the connector to ensure that the regulator easily fits underneath the tank dome. Pigtails bent during fabrication are primarily used where space is an issue, such as in an underground tank installation. As per figures 2 and 3 below, the regulator connections are 90-degree bend pigtails. Notice that the longer bent pigtail allows the regulator to be installed closer to the service valve.

Because pigtails can catch or trap debris from the propane tank over time, they should be replaced any time the regulator is replaced.

Remember that this type of connection does not require any sealant like Teflon on the thread. The seal is made through the pigtail cone and the valve seat.

Benefit 

• Flexible metallic connectors (pigtails or hogtails) provide a critical safety function as they allow for movement in the gas piping at the container. This flexibility reduces stress on rigid piping and fittings, absorbs vibrations and reduces shocks to the piping system at the container.
• Kinks in the flexible connector, which can restrict the flow of vapor and create a place for debris to collect, should always be avoided, and excessive bending or twisting can stress the tubing, which can lead to a crack and cause a leak.
• Copper offers a relatively inexpensive material for service line composition. Copper has the ability to be formed in long service line coils. This flexible copper can easily install around obstacles between the propane tank and the house, as opposed to the black pipe which requires 90-degree turns for manoeuvring around an obstruction. As a result, installation and material costs decrease, making copper an appealing material choice.

Corrosion concerns

• It is important to understand how flexible connectors can react with propane vapor. The interior surface of a copper flexible connector can become brittle as the hydrocarbon (propane) gas flows through it. Copper sulfate can form along the copper surface, resulting in flakes that can come loose and travel to the inlet of the regulator. Therefore, you don’t want to reuse or reposition flexible connectors that have been installed. It is important for propane professionals to be mindful of how debris can affect the safe operation of a propane (LPG) system.
• Flexible connectors (pigtails or hogtails) can catch or trap debris coming from the container. Debris can obviously cause a blockage that can obstruct the flow of gas vapor to the regulator. Debris like a corrosion (copper sulfate) flake or excess thread sealant can get stuck on the seat disc, resulting in the regulator orifice not sealing completely, which stops the regulator from reaching lock-up. Debris of any sort that enters the inlet of a regulator can cause the regulator to “creep,” which can lead to increased outlet pressure, causing the internal relief valve to activate.
• Although it may be a small item in the total propane vapor distribution system, remember that if you are replacing a regulator or switching a container, always replace the flexible metallic connector (pigtail or hogtail). By properly selecting and correctly installing these connectors, you are ensuring the safety of the operating system that helps ensure you provide clean, efficient propane energy to your customers.

Copper Line Considerations

In 1999, the International Association of Plumbing & Mechanical Officials (IAPMO) designated that copper tubing and fittings are allowable for gas-distribution systems, including propane. However, some individual states still have limitations on copper use for gas distribution tubing. Consumers should verify an individual state's laws with a certified propane professional before installing copper tubing.

Copper Limitations

Copper is typically corrosion-resistant but can develop problems if placed in specific soil types underground. Soils high in sulfate and chloride levels, deemed aggressive soils, can chemically react with the copper tubing surface. A catalyst for aggressive soil corrosion is water. Water within the soil, that cannot drain properly, provides a corrosion-friendly area for copper tubing. Installers must survey the installation site before laying any copper tubing, ensuring that the underground soil is stable for long term copper lines.

Copper Line Protective Measures

Propane (LPG) service lines must be installed at least 12 to 18 inches deep underground. This prevents damage to the line from vehicles or animals crushing the tubular shape, causing possible leaks. Copper lines can have protective tape or PVC (Polyvinyl Chloride) sheathed around the tube's exterior for extra protection against underground corrosion.

Mixing Metals

Copper is a metal that has Galvanic properties, developing corrosion when touching other metals, such as iron or steel. Copper lines must not mix with other metal line tubing. Installers should install pure and complete copper lines between the propane tank and the home.

Warning

Propane leaks can easily cause a fire hazard. Shut off the propane tank at its flow valve connection. Contact a propane service provider immediately for repairing the leak. Do not attempt to access the leak without a professional's guidance.