Flexible Rubber Couplings

Flexible Rubber Couplings                                                                                                                                                                                                                                                                                  

In the underground application, flexible rubber connectors are used to couple similar or dissimilar types of pipe.

The first manufacturer was Mission Rubber Coupling in the late 1950’s after the owner saw there was a need of a better way of coupling pipe together.

Size ranges are from 1-1/2”-27” but larger sizes can be manufactured when specific outside diameters are provided.

Couplings are made of rubber and PVC, the more rubber in the compound, the more flexible the coupling will be. Couplings are provided with two clamps made from stainless steel straps that use worm gear to tighten down with either a screwdriver or socket wrench.

Flexible Rubber Couplings

Standardized part numbers dictate what materials are being joined by flexible couplings.

For example, the 01 series joins clay to clay. The part number would then follow with the pipe diameters be joined (01-66 is to join 6” clay to 6” clay). All manufactures use these as a reference for SKUs while including minor additions for the own inventory systems (ex. 1001-66).

The common nomenclature is as follows:

  • 01 Clay to Clay
  • 02 Clay to PVC
  • 03 Clay to Ductile iron (DI)
  • 04 Concrete to Concrete
  • 06 Concrete to Plastic
  • 51 AC/DI to Plastic
  • 55 DI to DI
  • 56 PVC x PVC

Another type of flex coupling was introduced in the late 1970’s by adding a stainless-steel band around the flex coupling known as a non-shear coupling. This band helps to add extra strength when joining pipes, especially dissimilar pipes (ex. Clay to PVC).

Copper Tubing

The most widely used material in underground water service is Type K copper.

Available for water service in sizes 1/4” - 2”, it comes in coils of 40’, 60’ and 100’. Larger diameters are available up to 12” but come manufactured in straight lengths.

Copper tube is manufactured in strict adherence to ASTM B88 specifications with controlled inside diameter and inside diameter.

Copper is made from raw copper extracted through a mining process and turned into large cathodes or ingots with a 99.9% copper content after refinements. Scrap copper is widely used in pipe manufacturing as well due to lower cost. Tubing is made from a seamless process drawn from the plant.

Copper tubing is used due its high strength (1” = 1125 PSI) and long-life cycle.

Fittings copper tubing are brass fittings that are either connect via flare, compression or pack-joint for burial use. Solder joints are no longer accepted due to risk of failure at the joints.

Other materials used for water service are made of PVC with ratings of 100-200 PSI as well as braided pex-pipe.


There are various tools manufactured for the waterworks industry. Many were developed over time to aid in the field or to turn water on and off when needed.

Pipe wrenches, pipe shut-off tools, shut-off keys for main valves and services, pipe taps, test pumps and socket wrenches for repair clamps just to name a few.

Material is usually made of high-grade steel.



Castings date back to the mid 19th century and are used as access points for water, sewer, and storm lines for maintenance. They are all listed as confined spaces.

There are many sizes of manhole frames and covers in height, openings and widths.

They can be constructed of grey iron meeting specifications of AASHTO 105 or ductile iron, meeting AASHTO 360 either undipped or dipped in an asphalt coating.

Covers for manholes include solid, that can be marked with appropriate cover for water, storm, and sanitary. Inlet grates can be supplied for storm water drainage. Most manhole covers are round so they cannot fall into the manhole versus rectangular.

Other castings include drainage castings in the curb line known as curb basins. They are generally 3 pieces, including frame, back and cover.

There are different load types made such as non-traffic, medium duty, heavy duty & extra heavy. Traffic duty comprises of having a H20 designation for vehicle loads.

Testing for frames and cover must pass weight load testing under ASTM-A-8 specifications with non-traffic with a minimum testing of 1,000#, Medium duty of 18,000#, heavy duty of 25,000#, and extra heavy duty based on total wheels and weights, usually for airport applications.

Flexible Rubber Couplings