Fittings are devices used to connect pipes. Those used in DWV systems are called drainage fittings.
DWV fittings are made from many different materials, including copper, brass, lead, steel, cast iron, clay, glass, and various types of plastic. Cast iron and plastic are the most commonly used materials.
General DWV Fitting Requirements
The following are the general requirements for drainage fittings:
• Drainage fittings should not slow or block the flow of materials in the pipe. Because of this, sanitary drainage fittings are made with sweeps designed to allow for the smooth flow of materials in the system.
• The direction of hub type fittings should not go against the flow of the system, i.e., the waste should flow from the bell to the spigot end of the pipe.
Sanitary fittings are used to connect DWV branches to the main DWV systems. The branch inlets of these fittings may be reducing (going from larger pipe to smaller pipe). If so, they can be joined to the system without reducers.
The next slide presents some of the basic DWV fittings used by plumbers. These are bends, cleanouts, tees, and wyes.
The term bend is often used in reference to cast iron fittings. With other types of fittings, the term elbow is more common. To join pipes of different materials, plumbers use fittings called adapters.
Click on each type of DWV fitting to know more:
Bends are used to change the direction of a run of pipe, and are expressed as fraction of a complete circle.
Bends are available with heel inlets and side inlets to allow smaller lines to be connected to the bend.
Short sweep 1/4 bends and long sweep 1/4 bends may be used at the base of DWV stacks. They are required by various codes because the longer radius of their turn greatly decreases flow resistance and back pressure.
Double 1/4 bends (also called twin ells), are used to collect and combine the flow from two opposite runs into a single run of pipe.
Codes allow the use of vent ells only in vent lines. If they were placed in drainage or waste lines, their sharp turn radius would restrict the flow of materials.
Fittings are also available for cleanout. Cleanout fittings have internal threads on the branch fitting to accept a threaded cleanout plug.
A cleanout adapter may be installed in one end or branch of fittings to provide cleanout access.
Sanitary fittings are available in single and double patterns. The double pattern is used to connect two branch lines entering the system from the opposite direction. This allows for central placement of horizontal runs and vertical runs.
Sanitary branch fittings consist of tees, wyes, and a combination of the two. Sanitary tees are used for branches that run from horizontal to vertical. Sanitary tees are available with side inlet. The side inlet allows smaller drains to be connected from the right or left.
Sanitary wyes are used to provide a smooth-flowing DWV system, in keeping with code requirements. If the correct fittings are not used, soil and wastes may collect on the pipe wall opposite the branch.
Sanitary upright wyes are used to connect the vent stack to the lower ends of the soil and waste stacks.
Vents branches are used to join the upper end of the vent to the top of the soil and waste stacks. Inverted wyes may be used in place of vent branches.
Other DWV Fittings
Plumbers also make use of fittings such as sanitary combination and sanitary increasers.
A sanitary combination is a fitting that combines a wye and a 1/8-bend.
Sanitary increasers are used to enlarge the diameter of vent stacks and are usually placed at least 1 foot below the stack’s intersection with the roof.
Sanitary increasers are necessary in cold climates to keep condensing water vapor from freezing and gradually closing the vent opening. The loss of the vent could cause the loss of the trap seals, allowing sewer gas to enter the building.