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Lead was used for plumbing pipes by the Romans 2000 years ago, and the word "plumbing" is derived from the Latin word for lead, "plumbum." Lead pipes were used through the 1950s. As a result, the U.S. Environmental Protection Agency (EPA) is concerned even today that lead may leach out of lead pipes and copper pipes joined with lead solder and enter the water supply. Fortunately, lead on the inside surface of a pipe quickly reacts with sulfates, carbonates, and phosphates in the water to form a coating that keeps it from leaching out of the pipe. Experts believe, however, that the lead content in water is likely to exceed safe guidelines when the water is highly acidic or is allowed to sit in the lead pipes for a long time.

Plumbing supply pipes are made of copper, red brass, galvanized steel, and plastic. Galvanized steel pipe was the standard for water supply until copper took over in the 1960s. Steel pipe is strong and inexpensive, but is subject to corrosion, and eventually rusts and springs leaks. Steel pipes last from about 20 to 50 years. Mineral deposits build up inside, reducing the inside diameter and resulting in reduced water pressure at faucets.

Red brass and copper tubing offer the best corrosion resistance, with copper being less expensive, easier to assemble, more resistant to acids, and lighter weight than brass. Copper pipe lasts about twice as long as galvanized pipe. However, it costs nearly twice as much by length. Both flexible (soft temper) and rigid copper tubing can be soldered, but only the flexible copper tubing will accept compression fittings or flare fittings without soldering.

Iron (ferrous) pipes and large brass pipes use threaded connections. Copper pipes are joined with solder. Solder, which was formerly made of lead, is now a tin and antimony alloy. The molten solder is drawn into the joint. This allows piping to be set up without turning the parts to be connected, greatly facilitating installation. It also permits pipes with thin walls, because no threads have to be cut into their thickness. The smooth interiors contribute less friction to flowing water.

Plastic pipe is lightweight, low-cost, corrosion resistant, and easy to work with. It is available in flexible form for outdoor use, and as rigid pipe. Plastic pipe is made from synthetic resins derived from coal and petroleum. Rigid polyvinyl chloride (PVC, white or gray)

The design for the hair salon would involve a lot of equipment. Right from the start, Harry made sure that the engineers had spec sheets for all his client's equipment. There was just one problem. The client was looking for a special shampoo sink for the project, and was having trouble finding a supplier.

The engineer had to specify something so that the building department could review and approve the plans and the contractor could submit a bid. It was decided to specify plumbing coming up into the cabinet behind the sink, then out horizontally to the sink. The drawings were prepared and sent to the contractor and building department.

Meanwhile, the client found a supplier for the shampoo sink. Once construction began, the contractor needed the specifications on how the sink would be plumbed. Despite repeated calls to the sink supplier, Harry couldn't get technical specs for the sink.

When the sinks arrived, the contractor discovered that they were designed to be plumbed up the pedestal from the floor below. The plumbing was already installed in the cabinets behind the sink. It was possible to modify the sink to accept pipes from behind, but they would be exposed. Harry and the contractor decided to bring the plumbing from behind through a cutout in the pedestal. The exposed pipes were covered by a laminate panel to match the cabinets, giving a finished appearance and hiding the pipes.

and acrylonitrile-butadiene-styrene (ABS, black) pipes are suitable for various cold-water applications. Both ABS and PVC are thermoplastics, which can be molded under heat. Because of their sensitivity to heat, however, ABS and PVC are not used for hot water lines.

Chlorinated PVC (CPVC) pipe, which is usually cream color, may be used for hot or cold water. It is a thermoplastic and can be solvent welded, but it can be used at higher temperatures than ABS or PVC. Poly-butylene (PB) pipe cannot be welded with solvent, and uses compression fittings. It is flexible, and can be snaked through walls. It is also less susceptible to damage from freezing.

More access to plastic pipes must be supplied in case fittings need to be repaired than where soldered joints are used with metal pipes. Plastic pipe used for potable water is required to have a seal from the National Sanitation Foundation (NSF). Because plastic pipes are shockproof, they are used in mobile homes where vibration would be a problem for other types of plumbing.

Engineers determine pipe sizes by the rate at which the pipes will transport water when there is the most demand. Pipes in the supply network tend to be smaller as they get farther from the water source and closer to the point of use, since not all of the water has to make the whole trip. The sizes depend on the number and types of fixtures to be served and pressure losses due to friction and vertical travel. Water flowing through a smaller pipe is under greater pressure than the same amount of water in a larger pipe. Each type of fixture is assigned a number of fixture units. Based on the total number of fixture units for the building, the number of gallons per minute (gpm) is estimated. The engineer assumes that not all the fixtures are in use at the same time, so the total demand is not directly proportional to the number of fixture units. The interior designer needs to give the engineer specific information about the number of plumbing fixtures and their requirements as early in the process as possible.

Pipes sweat when moisture in the air condenses on the outsides of cold pipes. The condensation drops off the pipes, wetting and damaging finished surfaces. Cold water pipes should be insulated to prevent condensation. Insulation also keeps heat from adjacent warm spaces from warming the water in the pipes. When pipes are wrapped in glass fiber 13 to 25 mm (y-1 in.) thick with a tight vapor barrier on the exterior surface, the moisture in the air can't get to the cold surface. Hot water pipes are insulated to prevent heat loss. When hot and cold water pipes run parallel to each other, they should be a minimum of 15 cm (6 in.) apart, so that they don't exchange heat.

In very cold climates, water pipes in exterior walls 3 and unheated buildings may freeze and rupture. Avoid locating fixtures along exterior walls for this reason. If water supply pipes must be located in an exterior wall, they should be placed on the warm side (inside, in a cold climate) of the wall insulation. A drainage faucet located at a low point will allow the pipes to be drained before being exposed to freezing weather.

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