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R & D – Reamed and Drifted. Pipe commonly used in water wells having a special, heavy-duty coupling and a guaranteed I. D. clearance.

RF – Recovery Factor – Rating based on the efficiency of the product which is input required to raise 1 gallon of water 1 degree Fahrenheit.

Rail Fittings – Fittings with setscrews rather than threads, which hold pipes used for hand railings. Available in various sizes and configurations to suit a number of applications. Not used for plumbing or conduit.

Rated Storage Volume – Volume Quantity of water stored in a tank.

Raw Water – Water supplied to the plant before any treatment.

Reamer – A grinding tool used to level or remove burrs from valve seats in faucets so that the valve stem will fit properly.

Recessed Tub – A tub that has a decorative finish on one side only, and surrounded by three walls. The apron, or skirting, may not be included and must be ordered separately. The most popular style.

Recirculating Harness – PVC tubing setup that circulates water throughout a whirlpool system, delivering water to the jets.

Recovery – The amount of water in gallons that can be heated in one hour. (gph).

Recovery Capacity – The amount of water in gallons per hour raised 100 degrees F at a given thermal efficiency and BTU per hour input.

Red Water – Water which has a reddish or brownish appearance due to the presence of precipitated iron and/or iron bacteria.

Reducer – A pipe fitting used for joining pipes with different diameters together. A bushing is threaded on both the inside and outside.

Reed Switch – A serviceable, magnetic sensing switch that triggers the water flow to stop when the neck jet pillow (with magnet) is removed from the whirlpool.

Refill Tube – The tube that directs water from a ballcock into the overflow tube to refill the bowl after a siphon break.

Reflective Glass – Glass that bounces back at least some of the light that strikes it.

Relief Valve – A valve that opens to relieve excess temperature.

Repair Clamp – Sleeve type clamp used to repair a split pipe, held in place by bolts.

Return Circulation System – Tempered water from or near the point of usage which eliminates waste of hot water used for long runs and adds storage to the system.

Revent – Pipe installed specifically to vent a fixture trap. Connects with the vent system above the fixture.

Reverse Osmosis – A water treatment method whereby water is forced through a semi permeable membrane which filters out impurities.

Reverse Trap Water Closet – A water closet having a siphonic trapway at the rear of the bowl, and integral flushing rim and jet. Min. dimensions are 9″ x 8″ water spot and 1 �” ball pass.

Rich Mixture – A mixture of gas and air containing too much fuel or too little air for complete combustion of the gas.

Rigid Pipe – Pipe designed to transmit the backfill load to the foundation beneath the pipe. Rigid pipe must be supported on the bottom portion of the pipe.

Rim – The inside edge of a toilet bowl or the edge of a lavatory or sink.

Rim Holes – A series of small holes in the underside of a toilet rim, around the circumference of the bowl. Incoming water flows down into the bowl through these holes, creating a rinse effect or wash over the entire inner surface of the bowl.

Riser – A vertical metal or plastic tube or assembly that connects a faucet to the water supply stop valve. Usually made of copper. Metal Flex Risers are corrugated to facilitate bending. Also a supply line that rises from one story to the next.

Roller Hanger – A pipe hanger similar to a clevis hanger except that the yoke bolts to a roller rod instead of a metal strap. This roller rod supports the pipe and permits horizontal movement.

Roman Spout – Deck-mounted faucet spout.

Roof Drain – A drain installed at the low spot in a roof that channels water into a drainpipe to prevent pooling.

Roof Flashing – Sheet metal installed at any break in a shingled roofline to prevent leaks. Also around sewer vents, fluepipes.

Root Valve – A multi-port valve commonly used on gauges or switches in high pressure, high temperature, or under otherwise severe process conditions. Typically built with non-rotating and non-threaded stems.

Rough-In – Installation of the drain, waste, vent, and supply lines in a structure to the proposed location of each fixture.

Rough-In Dimensions – Standard shape of the front of a toilet bow, having dimensions of 14″ wide by 16 �” long from center of seat hinge holes to front outside rim edge.

Round Front Bowl – Standard shape of the front of a toilet bow, having dimensions of 14″ wide by 16 �” long from center of seat hinge holes to front outside rim edge.

Run – A complete or secondary section of pipe that extends from supply to fixture or drain to stack.

Running Trap – An in-line trap mounted in a horizontal drainpipe, where the inlet and outlet are parallel.


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