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There are basically two types of pipe, depending on its use--pressurized pipe and tubing for carrying drinking (potable) water, or pipe and tubing used for drainage, waste and ventilation (DWV) applications. DWV piping is always larger than pressurized pipe, which tends to be smaller than 1" in dimension. There are three basic types of pipe used for both pressurized and DWV applications: plastic, steel and copper.


Because it is easy to work with, lightweight and durable, plastic pipe is popular among do-it-yourselfers for both pressure and drainage applications. Installation costs are usually lower for plastic materials, but in some areas, its use in home plumbing systems is restricted. Check local codes to see how and when plastic pipe can be used in your area.

One of the major advantages to plastic pipe is that it will not rot or corrode.

When metal pipe is buried underground, care must be taken to drain water before temperatures drop below freezing. Otherwise, both pipe and fittings would rupture when freezing water expands. These precautions are not necessary with flexible plastic pipe. It can be buried a few inches below the surface or deep enough to protect the pipe against accidental damage from digging or cultivation.

A disadvantage for some types, such as flexible polyethylene, is that it cannot be used for hot water lines. Any plastic pipe used to carry drinking water should bear the National Sanitation Foundation mark (NSF-pw).

Piping made of ABS, CPVC and PVC is classified as rigid pipe; piping made of PE, PEX and PP is classified as flexible pipe.


* Polyvinyl Chloride (PVC) comes in sizes ranging from 1/2" to 2" and is always white in color. It has excellent chemical resistance, good crush resistance and impact strength and is fire resistant (self-extinguishing). PVC is used in pressure supply and drainage systems to carry water for golf-course sprinklers, agricultural irrigation, underground gas-distribution systems, industrial and chemical piping, corrosive fume ducting and crude-oil transportation.

Used primarily for cold water supply, PVC is rated by wall thickness and strength. Common ratings (from thickest to thinnest) are Schedule 40, which is the most commonly used type, Class 315, Class 200 and Class 125, which is generally used for irrigation. PVC is functional up to 120[degrees]F (maximum) in pressure and DWV applications.

* Chlorinated Polyvinyl Chloride (CPVC) has excellent chemical, crush and fire resistance, high-impact and tensile strength and is non-toxic. Functions at 200[degrees]F in pressure systems and non-pressure systems. CPVC does require special solvent cement different from cement used for other types of plastic solvent welding. Single-step solvent cements exist. However, before using, tell customers to check local building codes for acceptance. It is used in hot and cold water supply systems and hot and cold chemical distribution systems.

* Polyethylene (black poly) or (PE) has excellent chemical and crush resistance. Mainly used for cold water supply. Has high-impact strength and flexibility and good low-temperature performance. Functions in temperatures from -65[degrees] to 120[degrees]F in low-pressure applications and up to 200[degrees] in non-pressure applications. Pressure ratings for black poly are from 80 lbs. to 200 lbs. per square inch (PSI). Both 160 and 200 can be used for potable water if stamped with a NSF-pw stamp of approval.

Black poly is mainly used in low-pressure water systems, such as golf course sprinklers; to carry corrosive liquids and gases; as underground conduits and gas pipe reliners; in industrial and chemical laboratory drainage systems; and underground gas piping. Perforated PE is used as a corrugated drainage pipe for foundation drainage.

Although there are many types and sizes of plastic pipe available, the most popular for home use is flexible polyethylene pipe with 1/2", 3/4" or 1" inside diameter. This pipe is lightweight and can be cut with an ordinary sharp knife or a fine-toothed hacksaw blade.

* Crosslinked Polyethylene (PEX)--PEX and CPVC are the only flexible plastic tubing suitable for use with hot and cold water in pressure systems. PEX has excellent chemical resistance to acids and alkalis but is not suited for fuel oil, gasoline or kerosene distribution systems. PEX can be joined with heat fusion, flare, crimp ring or compression fittings. However, it is not solvent weldable. Several plastic and metal fitting designs are available for use with gray poly.

PEX has excellent strength characteristics. PEX is not to be used in continuously circulating hot water plumbing loops. It is rated to function at 180[degrees]F up to 100 psi. Do not use in applications where the temperature of the water could exceed 180[degrees]F unless specifically approved by local building codes--for example, a water heater relief line.

* Polypropylene (PP) has excellent chemical resistance, is resistant to sulfur-bearing compounds, lightweight, good tensile strength and salt-water resistant. It is stronger and more rigid than PE with a higher functioning temperature (190[degrees]F). PP is popular as a material for tubular products, such as P-traps, because of its high chemical resistance.


* PVC--Same as for pressure systems, but functions up to 180[degrees]F in non-pressure DWV applications.

* Acrylonitrile-Butadiene-Styrene (ABS) has good chemical resistance, excellent impact strength, especially at low temperatures, and maintains rigidity at higher temperatures. Maximum functional temperature is 180[degrees] for non-pressure systems. ABS is used in mobile home and residential drainage systems and as underground electrical conduits.

* Rubber Modified Styrene (SR) has good crush resistance, fair impact strength and moderate chemical resistance. SR is lightweight but brittle at low temperatures. Functions at a maximum of 160[degrees]F. SR is used for drainage and sewage systems, underground downspout drains, underground electrical conduits, septic tank absorption fields and foundation drains.


* Steel pipe is used primarily for carrying water, steam or gas. Available in both black and galvanized finish, it is made of wrought steel and sold in sizes from 1/8" to 6".

* Galvanized pipe is commonly used for water systems; black pipe for manufactured and natural gas. Galvanized pipe should never be used for gas installations. Plumbing codes in many areas require that black pipe, especially that used underground, be coated and wrapped.


* Soi! pipe is made of vitreous clay, bituminous fiber, plastic, drainage-type copper or cast iron. Each has certain advantages depending upon location, soil types and price. Copper and cast iron are more expensive, but serve better where rigidity is a must or where tree roots are massive enough to crush fiber or enter clay joints.

* Copper and plastic (where permitted) have advantages of pre-fabrication and long lengths. Cast iron pipe also comes in longer lengths. Black iron pipe used for steam and gas is similar to galvanized, but not treated for rust resistance.


Copper tube, used primarily for pressure-rated systems, is manufactured in five general grades and thicknesses.

* Type K--heaviest, used in municipal, commercial, residential and underground installation.

* Type L--medium weight; used most often in residential water lines. K and L are manufactured in hard (rigid 20' lengths) and soft (60', 100' and 200' lengths, the latter in smalter sizes).

* Type M--hard and thin (20' lengths and under). Recommended for light domestic water lines and is not permitted in some city codes or for underground use.

* Refrigeration--comes in 50' coils and rigid 20' lengths. Most refrigeration copper has moisture removed and ends sealed for better performance of refrigerants. It is often used in heater connectors. Flexible brass or soft aluminum pipe seems to be more efficient for gas transmission to household heating and appliances.

* Type DWV--drainage, waste and vent; rigid only and comes in 20' lengths.

* Most frequently stocked tube includes Type L soft in 3/8", 1/2" and 3/4" sizes and refrigeration in 1/4", 5/16", 3/8", 1/2" and 5/8". Smaller and larger sizes are available and may be obtained on special orders. If you stock sewer pipe, you may want to add DWV copper and fittings, if local conditions permit their use.

* Type K, L, M and DWV copper sizes are listed in nominal dimensions (actual outside diameter is 1/8" larger); refrigeration copper sizes are listed in outside dimensions. All copper is normally corrosion resistant and easily assembled with proper tools.


Types of water supply tubes include braided (stainless steel, nylon or vinyl); chrome-plated copper or brass; plastic and ribbed chrome. The most common size is 3/8", which represents the outside diameter of the tube.

Plastic is flexible and inexpensive but not designed for exposed connections. Ribbed chrome bends easily without kinking. Braided tubes feature pre-attached connector nuts at both ends and can be flexed to fit. Chrome-plated tubes are more rigid than other types.

Replacement connectors are available that come with different-size fittings to ensure they connect to most any valve or fixture. They can be used to replace old copper, corrugated and vinyl supply lines. Faucet connectors are available in lengths from 9" to 72"; toilet connectors in lengths from 6" to 20" and dishwasher connectors in lengths from 48" to 72".


Heat is lost from non-insulated water pipes. That means lost energy and increased heating costs, frozen pipes in winter and condensation dripping from water pipes.

* Pipe insulation corrects these problems by maintaining the water temperature in the pipelines to avoid letting water run to reach desired hot or cold temperature.

* Insulation lubricants may cause severe stress cracking of certain plastic materials. Only non-lubricated insulation products (rubber or polyolefin) should be used for plastic piping systems unless otherwise specified by the insulation manufacturer.

Wrap-on insulation includes fiberglass pipe wrap with a separate vapor-sealing tape that must be wrapped around the fiberglass. Plastic cork wrapping needs no separate vapor seal since it will not absorb moisture and is waterproof. Other wrap-on insulation includes vinyl foam, aluminum foil and polyethylene-coated duct tape.

* Foamed plastic tubing for covering pipes costs more than wrap-on types. However, the finished job is generally neater looking, and the material is quicker to install. It is available in sizes to fit either galvanized pipe or copper tubing.

* Mastic compound can be used to insulate large-diameter pipes, cold water tanks and similar surfaces that may be subject to condensation. Available in one-gallon cans that will cover approximately 6 square feet, this thick coating is applied in layers at least 1/4" thick.


Heating cables are designed to keep pipes warm and water flowing. Two types of heating cables are series and self-regulating. While both types of cables have a similar appearance--plugging into electrical outlets and wrapping around pipes--the actual functioning and installation techniques are very different.

* The heat of series cables is generated by a current-carrying wire and is maintained at a temperature that does not vary with the environment. Series heaters are available in pre-assembled lengths from 2' to 100'.

Because of the heating element, customers cannot cut it to length themselves. It cannot be overlapped onto itself without burning out, so customers must be sure that they purchase the right length.

Most series heaters cannot be used on plastic pipes. Moreover, while some series heaters can be used with insulation, others cannot.

* Self-regulating beating cables generate heat through the plastic material between the current-carrying wires. These heating cables regulate themselves automatically, providing more heat as outside temperatures drop and less as temperatures rise. Self-regulation allows the cable to be overlapped. The heating cable is typically on a reel in the store, and the customers cut off only what they need. Installation involves wrapping the heating cable around the pipe and valves and securing with a high-temperature tape.

Separate connection kits are purchased and put together by the customer at home. Some self-regulating brands also come in pre-assembled, shorter individual lengths. Self-regulating heaters can be used on plastic pipes and should be used with thermal insulation.

Both types of heating cables must be protected from mechanical damage and from water. In addition, both should be used with a ground fault circuit interrupter (GFCI).
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Title Annotation:Plumbing Supplies
Publication:Hardware Retailing
Geographic Code:1USA
Date:Aug 1, 2006
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