Tapped left or tapped right: what does that mean? We get asked this often. If a rad is tapped left it means the threads in the connections are counterclockwise, the opposite of conventional pipe thread. If a rad is tapped right, the threads are clockwise.
When installing a radiator it’s important to be aware of the size and the orientation of the tapping in the radiator. The vast majority of radiators are tapped left hand thread. This happens for two reasons. Firstly, for a rad with connections at opposite ends, in order to assemble the radiator one side is tapped left and the other tapped right to facilitate connecting the sections together when it was manufactured. Secondly, for radiators with the connections on the same side, the tapping was done left, to allow for connection to the system before unions were invented.
To make a connection to a radiator, you can either use left/right nipples or left/right bushings. The purpose of the bushing is to reduce pipe size from the size of the connection in the radiator to accommodate the piping size the rad will connect to. The pipe thread direction can also be changed using a bushing.
At Ironworks we offer a comprehensive line of bushings and nipples. There are situations where manufactured parts are not available in the sizes needed to complete the connection, but we are now able to create custom adapters for those crafty connections.