How to recognise an elbow, tee, reducer, coupler and stop-end, and what each one is for.
Recognising the shapes
Plumbing fittings come in a small number of standard shapes, and knowing them by sight is as useful as knowing how they joint.
An elbow changes the direction of a pipe run. A common example is a 90-degree elbow, but other angles are available; match the fitting to the route and service.
A tee has three openings and provides a branch from the main run. An equal tee has same-size connections, while a reducing tee changes size at one or more connections.
A reducer has one larger opening and one smaller one, and joins two lengths of pipe of different sizes in a straight line.
An equal coupler joins two pipes of the same size in a straight line. A reducing coupler also changes the bore, so check the stated connection sizes rather than relying only on its general shape.
A stop-end seals an open pipe end. When taking an unused water branch out of service, remove the redundant length and cap close to the live supply instead of leaving a long, stagnant spur.
Count the openings and compare their sizes when identifying a fitting. A tee has a branch; a straight coupler has two ends. The equal tee and equal coupler in the practice diagram keep the same bore, while its tapered reducer joins different sizes.