They are a type of quick connector along with quick disconnect couplings and quick disconnect fasteners. These terms are sometimes used interchangeably by different industries, and there is frequently overlap in their definitions.
Generally, quick release fittings are able to provide fast connections for pipes and hoses without the use of tools. They can be attached and removed by hand quite easily. There are no valves or seals, but the connections are typically leak proof. Fluids are free to flow through them, and if the fitting is removed, there are no shut-off valves to prevent the fluids from coming out, unlike quick couplings.
Quick release fittings are also called quick disconnect fittings and are usually as easy to remove as they are to install. If any extra effort is required, it is a basic twist-and-pull technique, though some fittings need a simple tool in order to be disconnected. Quick release fittings are hollow shells made of plastic, brass, stainless steel or aluminum; other materials such as glass reinforced resin are available as well. These fittings can accommodate high pressures and temperatures.
Quick release fittings are used with fluids, whether liquid or air, and many are resistant to chemicals or mildly corrosive substances. Fittings are commonly used in plumbing or sprinkler systems for water transport.
There are three common shapes for quick release fittings: straight, tee or a 90° elbow. These can be combined for more connections or for use in tight spaces with difficult angles. Most fittings are push fit or use hose barbs to make connections. Push fit quick release fittings use lubricated gaskets or stainless steel teeth to hold a pipe or hose in place once it is firmly inserted inside the fitting.
Installation is straightforward and takes only a few seconds to complete because it does not require flame, heat, crimping, twisting or any other action. Different fittings use hose barbs to make connections. Various hose barb designs are shaped like bolts and have threading on one side with a tapered end on the other. The tapered end has low ridges called barbs that catch and grip the material that slides over them. Stainless steel clamps are often used to encircle the fitting and keep the connection tight.
Other hose barb fittings are not threaded; hose barb unions for instance have two tapered ends and are used to join two hoses. The Society of Automotive Engineers has established certain standards, and JIC and SAE threaded hose barbs are manufactured accordingly. There are many variations of quick release fittings, and custom designs are available.