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O-Ring – Round rubber washer used to create a watertight seal, chiefly around valve stems.

OEM – Original Equipment Manufacturer

Oakum – Loosely woven hemp rope that has been treated with oil or other waterproofing agent; it is used to caulk joints in a bell and spigot pipe and fittings.

Obscure Glass – A glass that lets light through but is not totally transparent.

Oil Powered – A water heater that uses oil as its fuel source.

Offset – A tubular component which permits the offsetting of a drainage run in the same basic direction.

One-Piece Toilet – A toilet in which the tank and bowl are manufactured as a single vitreous china fixture. One-piece toilets usually have a lower profile than two-piece toilets.

Open Front – A colorless, odorless fuel derived from the earth, consisting primarily of Methane (CH4). Odors are added to aid in leak detection.

Orbital Weld – A circumferential, full fusion weld used to join together two lengths of tubing. It is a GTAW welding process. Usually to join coiled lengths.

Orifice – An opening through which gas is discharged and whereby the flow of gas is limited and/or controlled.

Outlet / Discharge – The opening through which the water exits the pump.

Outlet Sewer – Pipe section in a septic system which runs between the septic tank and the drainage field.

Outside Diameter / OD – The diameter of a pipe measured from the outside edge.

Overflow Hood – On a bath drain, the decorative hood concealing the overflow.

Overflow Tube – The vertical tube inside a toilet tank that directs water into the bowl in case the ballcock malfunctions. It is usually part of the flush valve. It prevents potential water damage caused by a tank overflow. A “constant-running” condition alerts the user to a problem. On most toilets, the overflow tube also has a refill tube flowing into it, which directs water from the ballcock through the overflow tube to the bowl, after a siphon break.


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Source: “Plumbing Terms” Standard Plumbing Supply. 11 Sept. 2008