No-Hub Couplings

How they changed the world of plumbing - and how, when, where, and why you should use them

In the 1960's No-Hub Couplings were the next best plumbing innovation to hit the market and transformed cast iron drainage pipe installations. This happened just before plastic piping became available and acceptable in the plumbing industry and transformed the industry all over again. In this article we hope to provide you not only a brief history but also useful information regarding the versatility of no-hub couplings and their ability to be used for plastic piping as well.

The History of No-Hub Couplings

example of a no hub coupling

No-hub couplings revolutionized cast iron drainage pipe installations from a hazardous, tedious, skilled craftsman trade, to a simpler, quicker, less tools needed, safer occupation.

Before no-hub couplings were invented, hub and spigot cast iron piping would be connected into fittings with hubs or bells by using lead, oakum, melting pots, burners, special clamps, cast iron ladles, joint runners and caulking irons.

All of these tools were needed in order to ensure the plumber could pour the melted lead into the fitting and get the lead to evenly flow around the entire pipe and seal the fitting properly. This technique was accepted as the best possible way to join and seal pipe. You not only had to be trained, you also had to have years of practice as first an apprentice and then as a journeyman, before you could be considered as a master plumber in this field.

In the 1950's the residential housing boom surfaced. The Servicemen's Readjustment Act of 1944, which came to be known as the G.I. Bill, gave military veterans access to affordable college education. This in turn led to highly-educated, productive employees entering the work force and American businesses were willing to pay top dollars for management and engineering skills. Inexpensive oil from domestic wells was helping the engines of industry to move forward. New advances in science and technology increased work place productivity. And since any would-be competitors in Asia and Europe were in the process of recovering from the effects of the devastation brought about by World War II, our economy flourished, the baby boom had begun and new housing was desperately needed.

With the housing boom in full swing, plumbing and building contractors came to the conclusion that connecting pipes with lead and oakum was no longer cost effective because it required too much time and labor. Builders realized they needed a much faster way to connect pipe and reduce their building costs. The American pipe industry found and created a solution with the shielded no-hub coupling design.

However, how could something so simple be better than lead and oakum? New ideas are not always readily acceptable because people tend to be skeptical until something proves to be better. By the late 1960's contractors began to realize the no-hub coupling was not just a "band-aid" but a viable quality product that was indeed solid and secure and was passing the test of time.

As you can see, the invention of no-hub couplings streamlined the drain pipe installation process tremendously, and with just a 15 minute training period needed, hub and spigot lead and oakum installations soon became a thing of the past.

When, Where, and Why You Might Need a No-Hub Coupling

Cast iron piping is still used in most commercial buildings like hospitals, hotels, vehicle dealerships, banks, office buildings, schools, lube shops and countless other facilities. Even though ABS or PVC piping can be used for commercial buildings according to the Uniform Plumbing Code (UPC), oftentimes other local or state building codes may specify cast-iron pipe be used due to various reasons. Some codes limit plastic piping to no more than two story buildings. Some buildings may fall under local codes for health or safety and cast iron piping may be specified because it is not susceptible to burning like PVC or ABS piping, should a fire occur.

Cast iron piping is often used in many residential multi-story housing projects because it provides a much quieter flow of waste water than either ABS or PVC plastics. If you have ever been in a room on the first floor of a two story building where ABS or PVC was installed and someone flushes the upstairs toilet, you would know what we mean.

Although no-hub couplings were designed for cast iron they are also a very handy way to repair ABS or PVC. They can be especially helpful when the piping is in a hard to reach spot or the pipe is unable to be moved in either direction to allow the repair to be made with a solvent (glue-on) coupling. The pipe can be cut to remove the damaged area and a no-hub coupling can be installed along with the replacement piping.

ABS and PVC schedule 40 piping have a slightly larger overall outside diameter than cast iron pipe. There is not a significant difference when comparing the outside diameter of 1-1/2" or 2" cast iron to 1-1/2" or 2" ABS/PVC pipe. For these two smaller sizes you could use a no-hub coupling to connect ABS or PVC directly to cast iron piping without a problem. However, if you are using a no-hub coupling to connect 3" or 4" cast iron to ABS or PVC then you will notice a more defined difference between the outside diameters of the cast iron and the ABS or PVC pipe.

To make it easier to adapt ABS and PVC to cast iron, the ABS and PVC fitting manufacturers created the ABS and PVC No-Hub Adapter fitting. One side glues over ABS or PVC and the other side is the same size as no-hub cast iron pipe. Without the use of these special adapters, the inner gasket of a no-hub coupling will stretch too much and not provide the best seal possible. Note: ABS and PVC are not compatible to glue together so if you are using PVC then you will need a PVC No-Hub Adapter fitting, and if you are using ABS you will need an ABS No-Hub Adapter fitting.

How to Install a No-Hub Coupling

No-Hub couplings have an inner gasket made of a synthetic rubber compound, polychloroprene (neoprene). The inner gasket is surrounded by an outer stainless steel shield or band with stainless steel worm clamps strategically riveted to the shield to keep them in place. Series 300 stainless is used for corrosion resistance. With the use of a No-Hub Torque Wrench, the installer applies 60 inch-pounds torque to the 5/16" hex-head screw for optimum and proper assembly.

Example 1
Step 1: Simply slide the outer stainless steel shield over and down the pipe first. Then put the inner gasket onto the pipe.

Example 2
Step 2: The inner gasket can then be placed on the end of the pipe and folded down in order to align the pipe back in place close enough to be folded back over and onto the pipe.

Example 3
Step 3: Fold the inner gasket back over onto the pipe.

Example 4
Step 4: And finally, slide the shield back over the gasket and tighten the clamps. For proper tightening use a 60 inch-pounds torque wrench

Not to be confused with...

no-hub couplingNo-Hub Coupling
flexible rubber couplingFlexible Coupling

No-Hub Couplings are often confused with Flexible Rubber couplings which are a much thicker walled rubber coupling with two stainless steel clamps but do not normally include a stainless steel shield. As defined in the Uniform Plumbing Code section 705.4.2. a mechanical joint shielded coupling for hubless cast-iron pipe and fittings shall have a metallic shield where installed aboveground. Flexible rubber couplings with stainless steel clamps, without a shield, are designed for use below ground.

The no-hub coupling shield is designed to adjust to variations in diameters of pipes to be connected. As the stainless steel worm clamps are tightened, the corrugated shield interlocks with itself. As further tightening occurs, pressure is exerted both parallel and crossways against the inner gasket, tightening it against the pipe and providing a solid reliable seal. The shield keeps the pipes aligned with each other, preventing sagging or shifting, which could cut or break the inner gasket. The gasket creates the seal between the pipes (or pipe to fitting) and also helps prevent the pipes or fittings from pulling out of the coupling.

We hope we've provided you answers to any questions you may have had about no-hub couplings and if not, please do let us know. As you can see, there are many uses for no-hub couplings that can make your plumbing experience a little easier and possibly more enjoyable yet still provide a sound, solid connection.

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