Whether for plumbing or ventilation, a flexible coupling works in the tight spaces and at the unusual angles that a traditional, rigid coupling simply can't handle. Flexible couplings are made of a variety of materials, including PVC, rubber, and metal, and each type belongs in a particular piping system. Learn about the types of flexible couplings, understand their applications and choose the type best suited to your repair or building project. Flexible Plastic Drain Connectors This type of flexible coupling performs a variety of repairs and modifications below kitchen and bathroom sink fixtures. Although not a PVC pipe, these couplings appear in a similar white color. Typically, each end of the flexible plastic drain connector attaches to a plastic drain tubing by means of a rigid compression fitting. Like the flexible area of the average drinking straw, the entire center segment of this type of coupling features a thin-walled, collapsible and expandable portion of tubing. The flexible portion of tubing expands or contracts to alter the coupling's length. The flexible drain connector usually twists and turns over 180 degrees and, once stretched into place, holds its new position. Flexible Rubber Coupling While the flexible rubber coupling proves useful across a variety of plumbing applications, its primary application is the installation and repair of drain, waste and vent lines. This type of coupling appears as a thick-walled, tubular piece of rubber. Flexible rubber couplings arrive as a straight cylinder, bent at a 90-degree or 180-degree angle or formed into a P-trap. ABS, PVC or cast iron drain line fits snugly into the openings at either of the flexible rubber couplings. Hose clamps attached to each end of the flexible coupling allow a plumber to tighten the fitting around inserted pipes. Flexible Ventilation Duct Coupling Heating, air conditioning and ventilation (HVAC) technicians use flexible duct couplings to create unusual twists and turns in ventilation and exhaust systems. This type of flexible coupling typically appears as an aluminum cylinder. The cylinder is composed of a series of interlocking rings. The end of each ring connects and slides within the end of the following ring, allowing an HVAC professional to twist and turn the cylinder into complex shapes, such as S shapes and offset U shapes.
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