Pipe Joints

Over the last 200 years there have been close to a hundred different types of pipe joints manufactured. This includes the Dawson Joint, Stewart’s Loose-Flange Joint, the Albion Loose-Flange Joint, the All Gunmetal Expansion Joint, the Cement Mortar Joint, the Push-On Restrained Joint, the Hot-Pour Compound Joint, the Ammonium Pipe Flange Joint With Aluminum Ring, and on and on and on.

Some of these were used only in plumbing or other ISP applications. Some were manufactured for only 20 or 30 years before they were discontinued. And some are simply variations of standard joint designs.

Not including the ancient pipes and joints from thousands of years ago, the oldest pipe joints are Bell & Spigot joints on cast iron pipe (also known as Ball & Spigot). The oldest known Bell & Spigot joint in the United States was used on cast iron pipe in 1785.

Throughout the 1800’s the Bell end of Bell and Spigot joints were cast separately from the pipe, then pushed onto the pipe, and this is rather noticeable. Somewhere around 1900 or so the Bell end was now being cast as a part of the pipe.

The Mechanical Joint was developed in the 1920’s, and the Push-On Joint was developed in 1956. Today there are a wide variety of pipe joints being used.

One of the many interesting pipe joints is the “Bell and Spigot Lap Weld Joint” This is steel pipe with a thin bell end to it. The smaller “spigot” end is pushed in to the bell end, then the steel is welded. This type of pipe usually has concrete lining. These are common for steel water transmission and sometimes for wastewater transmission.

Almost any pipe we see above ground will be a flange joint, either ductile iron or steel. This is also true inside of manholes. A poly water pipe will convert to iron with flange joints where it enters a manhole – then convert back to poly pipe outside of the manhole. So, although there are numerous types of joints, the most visible pipes will tend to be restricted to flange joints only.

The illustrations below do not represent at all the diverse options in joint design, but are only meant to help give an easy identification for common joint designs. The locking joint is the only one here that is shown in cross section to help clarify how it functions.

Saddle Fusion – Poly Pipe only
Thread & Bonded (T&B) – also called Screwed Socket
Bell & Spigot – the example shown is the Open-Type Socket and Spigot
Butt Welded Joint for Steel pipe or Butt Fusion for Poly Pipe
Locking Joint
Push-On Joint
Flange Joint – the example shown is the Plain-Faced Flange Joint
Mechanical Joint – the example shown is commonly used as an additional brace for Flange or Bell & Spigot
Saddle Mechanical
Collar Joint – commonly used on sanitary sewer pipes