5703.6.9 Flexible Joints
Flexible joints shall be listed and approved and shall be installed on underground liquid, vapor and vent piping at all of the following locations:
- Where piping connects to underground tanks.
- Where piping ends at pump islands and vent risers.
- At points where differential movement in the piping can occur.
Fiberglass-reinforced plastic (FRP) piping is not required to be provided with flexible joints in locations where both of the following conditions are present:
- Piping does not exceed 4 inches (102 mm) in diameter.
- Piping has a straight run of not less than 4 feet (1219 mm) on one side of the connection where such connections result in a change of direction.
In lieu of the minimum 4-foot (1219 mm) straight run length, approved and listed flexible joints are allowed to be used under dispensers and suction pumps, at submerged pumps and tanks, and where vents extend above ground.