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P Trap – P-shaped section of drain pipe that water is trapped in, blocking gases from escaping through the drain. Prevents sewer odors from escaping into your home.

P & T Relief Valve – Pressure and Temperature Relief Valve – Same as T & P

PB – Polished Brass finish

PDI – Plumbing and Drainage Institute

PE – Polyethylene plastic material. Also Plain End pipe.

PEX – Cross-linked polyethylene. PEX tubing is commonly used for hydronic radiant floor heat, but increasingly also used for water supply lines. Stronger than PE.

P O Plug – Lavatory drain with separate removable plug.

POS – Porcelain on Steel. A finish commonly used on sinks and tubs.

PP – Polypropylene Pipe

PPM – Parts Per Million. A unit of measure for impurities in water.

PR – Pressure Regulator. Usually required if water pressure ever exceeds 80 PSI on potable water supplies inside a structure.

PSI – Pounds per Square Inch

PSIG – Pounds per Square Inch Gauge

PVC – Polyvinyl Chloride. A rigid white or cream-colored plastic pipe used in non-pressure systems, such as drainage, waste, and vent systems.

PVD – Physical Vapor Deposition. A modern plating process used mostly with polished brass or gold finishes on faucets. Vaporized zirconium reacts with nitrogen and other gases to form a very durable surface, which will not tarnish or discolor.

Packing – Fibrous material that is used on faucets to prevent leaks.

Packing Nut – The nut that holds the stem of a faucet in position & holds the packing material.

Parallel System – Two or more identical size heaters piped with water connections, that is, cold water travels equal distance into the inlets of the heaters from a “T” connection and hot water travels equal distance from the outlet of the heaters to a “T” connection.

Peak Hour Demand – Time when the largest demand for hot water is needed.

Peak Load Period – The period of the day in which the system has the greatest demand.

Pedestal Lavatory – A lavatory in which the bowl is supported by a single pedestal leg.

Penal Valve – A commercial flush valve, so-named because of its use in penal institutions.

Perfect Vacuum – Theoretically, space without matter in it. A perfect vacuum has never been obtained.

Perforated Pipe – Pipe designed to discharge water through small, multiple, closely spaced orifices or nozzles, placed in a segment of its circumference for irrigation purposes.

Petcock – A small faucet for draining liquids or relieving air pressure.

Phase – For ease of production and distribution, A. C. is distributed in what is known as a 3 phase supply using three active wires and one neutral wire.

Phenol – A poisonous and carcinogenic chemical often found in municipal water supplies. Also known as carbolic acid, phenol is a benzene derivative.

Pickling – Pipe immersed into acid bath for removal of scale, oil, dirt, etc.

Piezo Switch – A device that provides a supply of water or its disposal, e. g. sinks, tubs, toilets.

Pilot – A small burner used to ignite the main burner.

Pin – External (male) threaded end of pipe.

Pipe Dope – Industry term for pipe-joint compound. Substance applied to threaded fittings to create a watertight seal.

Pitch – Downward slope of a drain pipe in the direction of the water flow.

Pivot Door – A shower door that rotates on two metal pivots at the top and bottom of the door.

Plumb – Precisely vertical. Also to test for, or to make vertical. Also to perform plumbing work.

Plumber’s Putty – Pliable putty used to seal joints between drain pieces and fixture surfaces.

Plumbing Tree – Prefabricated set of drain waste, vent, and supply lines.

Plunger – A rubber suction cup approx 6″ in diameter attached to a wooden dowel handle used to free drain clogs.

Pneumatic – Pertains to devices using compressed air.

Point of Use – Small water heater used for remote locations.

Pop-Up Assembly – The drain mechanism of a faucet installed on a lavatory. The drain stopper “pops” up and down.

Pop-Up Drain – Type of drain assembly for lavatory and bath. When a lavatory lift rod or bath overflow plate lever is lifted, the pop-up drain closes so the lavatory or tub retains water.

Poppet – Valve that rises perpendicularly to or from its seat.

Porcelain – White ceramic ware that consists of quartz, kaolin, and feldspar. It is fired at high temperature on steel or cast iron to make the surface of some bathtubs, kitchen sinks, and bathroom lavatories.

Porcelain Enamel – Vitreous enamel. Often refers to pressed steel products with a porcelain glaze.

Porosity – A measure of the volume of internal pores, or voids, in ion exchangers and filter media; sometimes expressed as a ratio to the total volume of the medium.

Port – An opening in a burner head through which gas or an air-gas mixture is discharged for ignition.

Positive Displacement Pump – Known as a “PD pump. ” Gear, sliding vane, progressive cavity, lobe etc. the capacity determined by the pump speed. The maximum head is determined by the horsepower available and the casing strength.

Portable Water – Water that is suitable for drinking.

Potentiometer – An adjustable resistor used to vary the sensing distance of the touch-less faucet.

Powder-Coat – A technique for applying paint to aluminum shower door frames. The aluminum is covered with a powder of dry paint particles and is baked in an oven. This causes the powder to melt and harden into a tough, colorful finish.

Power Venting – Mechanical draft exhaust to outside, usually utilizing room air to support combustion.

Pre-Charged Tank – A water storage tank pre-charged with air at factory featuring a vinyl bag to separate water from air which prevents water-logging. This tank design provides greater draw-down than standard tanks. Pre-charged tanks do not require air volume control.

Pre-Heated Water – Water that has been tempered (heated) for inlet supply.

Pressure Balanced Valve – A shower mixing valve that automatically maintains balance between incoming hot and cold water supplies by immediately regulating fluctuations in pressure. As a result, temperature remains constant, though the outlet pressure may drop. Also called an anti-scald valve.

Pressure Head – Pressure in a plumbing system. The unit of measure which is the vertical force exerted by water at a depth of one foot.

Pressure Loss – The term given for the loss of pressure that occurs whenever water moves through a pipe or when water moves uphill against the force of gravity. If the total pressure loss in a piping system exceeds the available static water pressure the water will not flow.

Pressure Reducing Valve – A valve that automatically reduces inlet water pressure to a specified value at its outlet under static cold water conditions.

Pressure Regulator – A device for controlling and maintaining a uniform outlet gas pressure.

Pressure Tank – Device used to pump water from a well.

Pressure Tubing – Tubing used to conduct fluids under pressure or at elevated temperatures or both, and produced to stricter tolerances than pipe.

Primary Air – Air which is mixed with gas before the gas leaves a burner port to burn. Ideal burning condition generally is 10 cubic feet of air per one cubic foot of gas.

Primary Air Inlet – The opening(s) through which primary air is admitted into a burner.

Priming Jet – Opening in bowl through which tank-supplied water flows, designed to propel waste up into the trapway.

Pull-Out Spray – Single-control kitchen faucet which offers a retractable hose and spray-head to be used for food preparation and cleaning.

Public Sewer – A common sewer directly controlled by public authority.

Pumping Level – The lowest water level reached during pumping operation.

Purged Line – A plumbing line in which the faucet has been opened and allowed to run for a specified length of time, usually1-5 minutes.


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