Threaded pipe, also referred to as steel or iron pipe, carries hot and cold water to sinks, fixtures and radiators. In larger diameters, it serves as drain, waste and vent pipe. Today, copper and plastic have taken over most of threaded pipe’s duties, but you may need to repair existing pipe -- and it continues to be used for gas piping.
Galvanized pipe is rust resistant and used for water lines. Black pipe is less expensive but susceptible to rust and should be used only for indoor natural gas and propane lines. Usually, you can have pipe cut to exact lengths and threaded at your local hardware store for a small fee. Standard nipples, short pieces of pipe threaded on both ends, are normally kept in stock. Any time you work with threaded pipe, keep these tips in mind:
- Loosen rusted or stubborn joints by applying penetrating oil and using a large pipe wrench or a cheater bar on the wrench handle to gain leverage.
- Don’t hammer on pipes. Hammering can loosen mineral deposits, which will clog valves and faucets.
- Check for leaks in gas-line fittings by brushing soapy water around joints, then watching for bubbles.
- Many electrical systems are grounded by the cold-water pipes, so replace any grounding wires you remove.
Tapered threads on threaded pipe provide an ever-tightening
seal as a pipe and fitting are screwed together making threaded pipe joints
particularly strong. Female fittings and couplings are likewise tapered. 
When
measuring, account for the distance the pipe and its fittings overlap once joined. Mea sure distance between fit tings and add 1/2 in. (19 mm) per threaded end for 3/4-in, pipe. For 1/2- in.
pipe, add 7/16 in. (11 mm) per threaded end. 
Wrap Teflon plumbing tape in clockwise direction around
threads to lubricate, protect and seal joints. Use at least three clockwise
wraps to provide a tight seal.(continue ...)
Recommended Reading
Illustrated Guide to the International Plumbing and Fuel Gas Codes
Issues covered: chief plumbing inspector, plumbing chief, local plumbing official, maximum gas demand, total dfu, lint interceptor, peak draw period, service supply pipe, receiving fixture, correct pipe size, indirect waste pipe, horizontal branch drain, circulating pump returns, diaphragm pressure tank, clear water waste, sand interceptor, most remote outlet, horizontal drainage pipe, building drainage system, interactive multimedia video that shows, sanitary drainage system, grease interceptor, maximum vertical drop, waste receptor, water service pipe.
For anyone involved in home plumbing installation or repair...Accessibly written by Howard C. Massey (a master plumber with over 30 years of experience), Illustrated Guide To The International Plumbing and Fuel Gas Codes is a solid manual developed expressly to make the new 2003 international pumbling and fuel gas codes understandable to everyone. Extensive instructions, diagrams, self-test questions and answers, clarify the complexities of vent systems, sanitary drainage systems, hot water supply systems, gas piping, and a great deal more. A direct, no-nonsense resource, Illustrated Guide To The International Plumbing and Fuel Gas Codes is an authoritative reference confidently recommended for anyone involved in home plumbing installation or repair.
Basic Plumbing With Illustrations
Issues covered: service supply pipe, peak draw period, drainfield absorption area, plumbing plans examiner, water service supply, bathtub waste, minimum toilet facilities, water closet bowl, soil pipe cutter, ratchet threader, water closet trap, water service pipe, combination faucet, water main pressure, interactive multimedia video that shows, water closet tank, inlet tee, sanitary cross, overflow rim, cutting plastic pipe, hydropneumatic tank, asphaltum paint, pipe compound, compression faucet, chain vise.
Reviews:
Quality reference material: Basic Plumbing with Illustrations is a
handy reference book for designers, engineers, and draftsmen. There
are a lot of illustrated examples showing best practices when laying
out residential and light commercial plumbing that minimize extra fittings,
are UPC compliant, and work for stacked and flat systems.
Also handy are rough-in dimensions for common fixtures, drain, waste and vent sizing charts, and cold and hot water supply sizing info.
that includes a neat explanation of solar hot water heating methods.
this reference goes hand in hand with another Massey authored Publication
entitled "Planning, Drain, Waste, and Vent Systems".
Deal for students, apprentices and practicing professionals: Now in a completely revised and updated edition, Howard Massey's Basic Plumbing With Illustrations is the definitive "how to" manual for installing code-approved plumbing in residential and light commercial buildings. Systematically laid out in twenty-three sections, Basic Plumbing With Illustrations covers all of the fundamentals of the plumbing trade including planning and sizing, installation, maintenance, common layout, materials, and code requirements. Invaluable and practical information is provided on inspections, floor plans and plot plans, drawing and reading isometrics, code definitions, and materials. Profusely illustrated with hundreds of charts, tables, installation diagrams, and rough-in measures, Basic Plumbing With Illustrations is enhanced further with a glossary of plumbing terms, plumbing abbreviations, extensive study questions at the end of each section, and a section with all the correct answers. This is the ideal text for students and apprentices, as well as practicing professionals in the field.
Everything is explained in this guide: This book shows you everything about plumbing, including septic systems, solar water heaters, and hooking up swimming pools and spas--not to mention the basic and industrial plumbing fixures and techniques. This book is extremely interesting.
Recommended Products
- NONE ICE-800 Ice Maker Hook-Up Kits (25-ft Bagged Plastic Tube) 25-ft Kit With Plastic Tube; Bagged;Includes 1 each: ; Roll of copper tubing; Self-piercing saddle valve; 1/4" compression union; 1/4" compression x 1/4" flare adapter.
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Loosen and tighten threaded steel pipe and fittings using a pipe wrench. The wrench has sharp teeth that bite into pipe and an upper jaw that pinches pipe as the wrench is turned. Always use two pipe wrenches, one to twist the pipe and one to hold the adjacent fitting.
Smart shopping: Shutoff Valves
When you visit a well-stocked plumbing supply store, you’ll discover dozens of shutoff valves for virtually every type of pipe, fitting and application. They’re commonly made of plastic, solid brass or chrome-plated brass. The valves can be connected by soldering, with threaded connections or with compression joints. Select a valve based on intended use and space limitations. Those marked WOG can be used for water, oil and gas. The heart of the valve—the internal shutoff mechanism -- will be one of only three types: stop, gate or ball. Stop valves are most often used as shutoffs for such fixtures as sinks, toilets and outdoor faucets.
Stop valves are washer-type valves that seal by screwing a rubber gasket against a seat. Flow is inefficient because the fluid takes a circuitous route. The valve must be oriented correctly so flow goes against bottom of rubber gasket. Gaskets sometimes need replacing.
Gate valves have a wedge-shaped brass gate that lowers into a machined slot to close the valve. This valve allows full, unobstructed flow for fluid. It should either be completely open or completely closed; water flowing through a partially open gate valve wears away the metal and causes premature failure.
Ball valves employ a stainless-steel ball with a port
drilled through it that pivots in plastic bushings. It allows full or
partial flow and completely opens and closes with only a quarter turn.
In the closed position, the lever is perpendicular to the pipes; when
open, it’s parallel. 