Pipes, Fittings, and Valves

Share:

These materials may be made of metal or plastic. Plumbing components made of bronze and brass contain 3% to 8% lead. Lead serves two purposes in the copper alloys from which these materials are manufactured. First, lead aids in the manufacturing process by providing lubrication and preventing chipping during the metal-working process. Second, the lead in the alloy improves product performance. Federal law limits the amount of lead to 8% that may be contained in plumbing materials, except flux and solder, installed into public water-supply systems.

Lead compounds may also be present in some plastic plumbing components. Lead may be used in the manufacture of the plastic plumbing products as a plasticizer. Plastic plumbing components that are certified by the NSF International do not contain lead. Plastic materials certified by NSF are recommended for potable water plumbing applications.

Lead Warning
Many older homes have lead pipe water systems. Many newer homes have copper pipe water systems which have been soldered together with solder containing lead.
This means that drinking water may contain lead. Exposure to lead may cause brain and nervous disorders, anemia, high blood pressure, kidney and reproductive problems, decreased red blood cells, slower reflexes, and even death.
The lead collects in the kidneys, liver, and brain. Unlike many other chemicals, once lead enters a person's system, it cannot be removed. Exposure to even small amounts over a period of years can cause irreversible damage.
Use only lead-free solder when working on plumbing projects.
Also, if it has been six hours since the water system was last used, turn on the water and let it run for a few minutes before drawing water for drinking or cooking. However, do not waste this water. It may be used for such things as watering plants.
Having water tested for lead content by an EPA-certified laboratory is recommended.
Additional information about lead in drinking water is available from the Environmental Protection Agency's Safe Drinking Water hotline, 1-800-426-4791. It will provide information about EPA-certified laboratories that test for lead in drinking water.

PIPE

The heart of home plumbing systems is pipe, whether for supply or waste drainage. Waste piping is always larger than water pipes, which tend to be smaller than 1" in dimension. Normal inventory consists of four kinds of pipe-steel, plastic, copper and soil.

STEEL PIPE

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.

Sizes for Wrought Iron and Steel Pipe
Nominal Size in InchesOutside Diameter in InchesInside Diameter in InchesNo. of Threads Per Inch
1/40.5400.36418
3/80.6750.49318
1/20.8400.62214
3/41.0500.82414
11.3151.04911-1/2
1-1/41.6601.38011-1/2
1-1/21.9001.61011-1/2
22.3752.06711-1/2
2-1/22.8752.4688

PLASTIC PIPE

Because it is easy to work with, lightweight and durable, plastic pipe is popular among do-it-yourselfers. Installation costs are usually lower for plastic materials, but in some areas its use in home plumbing systems is restricted; check on where and how local codes will allow plastic pipe to be used.

Polyethylene and polybutylene plastic pipe is flexible and can be cut with a pocket knife or a special cutter. One of the major advantages of plastic pipe is that it will not rot or corrode.

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 have the seal of the National Sanitation Foundation.

Following is a list of common plastic pipes and their characteristics.

Polyvinyl Chloride (PVC) - excellent chemical resistance, good crush resistance and impact strength, fire resistant (self-extinguishing). Is functional up to 120 degrees F in pressure systems and 180 degrees F in non-pressure systems, such as drain, waste and vent (DWV) applications.

Used in pressure supply and drainage systems to carry water for uses such as golf-course sprinklers and agricultural irrigation, and in underground gas-distribution systems, industrial and chemical piping, corrosive fume ducting and crude-oil transportation.

Chlorinated Polyvinyl Chloride (CPVC) - excellent chemical, crush and fire resistance, high-impact and tensile strength, and is nontoxic; CPVC can be used for hot and cold-water applications. Functions at 180× F in pressure systems and at higher temperatures in low- and non-pressure systems. CPVC does require a special solvent cement different from cement used for other types of plastic welding.

It is used in hot and cold water-supply systems and hot and cold chemical-distribution systems.

Polyethylene (PE) - excellent chemical and crush resistance. Has high impact strength and flexibility and good low-temperature performance. Functions in temperatures from -65o to 120 degrees F in low-pressure applications and to 200 degrees in non-pressure applications.

PE is 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.

Polybutylene (PB) - only flexible plastic tubing suitable for use with hot and cold water in pressure systems. PB has excellent chemical resistance to acids and alkalis, but is not suited for fuel oil, gasoline or kerosene distribution systems.

Polybutylene can be joined with heat fusion, flare or compression fittings. However, it is not solvent weldable. Several plastic fitting designs are available for use with PB.

Polybutylene has excellent strength characteristics. Manufacturers of PB claim that should water freeze inside, the tubing will not burst. However, some fittings used with PB will break under ice expansion.

PB is rated to function at 180× F up to 100 psi; higher temperatures can be tolerated with a relatively small reduction in pressure.

Acrylonitrile-Butadiene-Styrene (ABS) - 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 to provide gas service and as underground electrical conduits.

Rubber Modified Styrene (SR) - good crush resistance, fair impact strength and moderate chemical resistance. SR is lightweight but brittle at low temperatures. Functions at a maximum of 160 F.

SR is used for drainage and sewage systems, underground downspout drains, underground electrical conduits, septic-tank absorption fields and foundation drains.

Polypropylene (PP) - excellent chemical resistance, resistant to sulphur-bearing compounds, lightweight, good tensile strength and saltwater resistance. Stronger and more rigid than polyethylene with a higher functioning temperature (190 degrees F), polypropylene is popular as a material for tubular products, such as P-traps, because of its high chemical resistance.

Polyacetal (ACETAL) - excellent resistance to paraffins and solvents, high resistance to surge fatigue, nontoxic and approved for potable water. ACETAL is used for process systems; solvent handling; agricultural chemicals, crude-oil and natural-gas distribution systems.

Polyacetal is also used to manufacture faucet bonnet and valve stems.

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.

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.

To install flexible plastic pipe, the homeowner simply unrolls a coil of plastic pipe; couplings are not required unless the pipe is cut.

Semi-rigid and rigid plastic pipe, which is sold in 10' to 20' lengths, does require coupling.

Depending on the chemical composition of the pipe, pieces are joined with an insert coupler using metal straps to hold the coupling to each section of pipe or with a coupler that is sealed with a pipe cement. This cement creates a chemically fused bond between coupling and pipe that is as strong as the pipe itself. The exception is PE, which cannot be welded with cement.

Most plastic pipe can be joined with and worked into metal plumbing with the use of proper adapters or transition fittings.

Rapid technical advances in the manufacture and use of plastic pipe have made it imperative for consumers to follow the manufacturers' information on use, installation and pressure ratings of the pipe and fittings.

One area where these changes are most evident is in supply tubing. Supply tubing has gone through a metamorphosis from copper to corrugated copper to polybutylene and vinyl supply tube. Vinyl supply tubing is easy to hook up, and with its flexible "give" will alleviate a mild water-hammer condition created by many single-lever faucets with quick shutoff. Stainless-steel braided flexible supply connectors are another form of supply tubing. Stainless-steel braiding encases a nontoxic synthetic polymer or neoprene rubber core suitable for both hot and cold water.

Manufacturer claims include high-burst pressure ratings (1,500 psi to more than 2,400 psi), resistance to embrittling, and crimping on fittings that won't creep or blow off.

No cutting or flaring is involved which eliminates pipe bending, soldering and special tools.

Stainless steel braided connectors are available for faucets and toilets as well as for water heaters, water softeners, dish and clothes washers, hot tubs, etc.

Similar connectors use nylon braiding which offers a reduced burst pressure in the 600 psi range.

SOIL PIPE

Soil pipe is made of vitreous clay, bituminous fiber, plastic, drainage type copper (DWV), 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 prefabrication and long lengths. Cast iron pipe also comes in longer lengths.

COPPER PIPE

Copper pipe - is manufactured in five general grades and thicknesses.

Type K - heaviest; used in municipal, commercial and residential construction.

Type L - lighter than K; 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 smaller sizes).

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

Refrigeration - 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, but has a tendency to build a crust of corrosion on the inside if gas has any trace of sulphur. 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.

Type K, L, M, and DWV copper sizes are listed in nominal dimensions; refrigeration copper sizes are listed in outside dimensions. All copper is normally corrosion resistant and easily assembled with proper tools.

Sizes of Type K,L,M Copper Tube
Nominal Size in InchesOutside Diameter in Inches
3/81/2
1/25/8
3/47/8
11-1/8
1-1/41-3/8
1-1/21-5/8

Pipe Data At A Glance
Type of PipeEase of WorkingWater Flow EfficiencyType of Fittings NeededManner Usually StockedLife ExpectancyPrincipal UsesRemarks
Brass, ThreadedNo threading required. Cuts easily, but can't be bent. Measuring a job rather difficult.Highly efficient because of low friction.Screw-on Connections12 ft. rigid lengths. Cut to size wantedLast life of buildingGenerally for commercialRequired in some cities where water is extremely corrosive. Often smaller diameter will suffice because a low friction coefficient
Copper - HardEasier to work with than brassSame as brassScrew-on of Solder Connections12 ft. rigid lengths. Cut to size wantedSame as brassSame as brass 
Copper - SoftEasier to work with than brass or hard copper because it bends readily by using a bending tool. Measuring a job not too difficultSame as brassSolder Connections, Flare FittingsCoils usually softSame as brassSame as in residential installations 
Copper Tubing - FlexibleEasier than soft copper because it can be bent without a tool. Measuring job is easy.Highest of all metals since there are not nipples, unions or elbowsSolder or Compression connections, Flare Fittings3 wall thick-nesses: 'K' Thickest, 'L' Medium, 'M' Thinnest. 20 ft. lengths or 15 ft., 30 ft. or 60 ft. coils (Except 'M')Same as brass lines only. Check Code before using'K' is used in municipal and commercial construction. 'L' is used for residential water lines. 'M' is for light domestic low friction coefficientProbably the most popular pipe today. Often a smaller diameter will suffice because of low friction coefficient
Wrought Iron (or galvanized)Has to be threaded. More difficult to cut. Measure- ments for jobs must be exactLower than copper because nipple unions reduce water flow.Screw on connectionsRigid lengths up to 22 ft. Usually cut to size wantedCorrodes in alkaline water more than others. Produces rust stainsGenerally found in older homesRecommended if lines are in a location subject to impact
Plastic PipeCan be cut with a saw or knifeSame as copper tubingInsert couplings, clamps; also by cementRigid, semi - rigid - 10 ft., 20 ft. lengths. FlexibleLong life; resists rust / corrosionFor cold water installations. Used for well.Lightest of all; weighs about 1/8 of the weight of steel

TRAPS AND TUBULAR GOODS

TRAPS

Plumbing fixtures are equipped with either a P or S trap, which is frequently fitted with a clean-out plug on the bottom. The trap bend holds water which prevents odors from backing up into the home.

Drum and bottle-type traps for bathtubs or kitchen sinks consist of a cylindrical metal box or settling basin attached to the waste pipe. They are generally provided with a screw-cap cover that can be removed when cleaning is necessary.

In most areas 1-1/4" chrome-plated brass traps are used in lavatory drains, and satin-finished or nickel-plated brass 1-1/2" traps are standard equipment on residential kitchen sinks. (Satin finish is unpolished chrome-plated tubular).

Plastic P and J traps can be used in retrofit as well as new plumbing work with adapters and transitional couplings to connect plastic with other materials.

Corrugated flexible plastic drain is useful when installing new sinks or vanities with older drain systems. Many times the drain from a new installation will not line up with the old drain pipe. Corrugated, plastic drain pipe allows the d-i-yer to connect misalignments by as much as several inches.

TUBULAR GOODS

Garbage disposers, dishwashers and special kitchen sinks require tubular brass goods including P traps, S traps, J bends, repair traps (with slip-joint nuts on both ends), continuous wastes for sinks with double compartments, tailpieces that connect sink strainers to continuous wastes, branch tailpieces that connect dishwasher drains to sink wastes, extensions to slip (straight tube lengths with slip-joint nut), and extensions to solder (straight tube with bell end for a sweat extension).

These are primarily used in adding disposers to existing sinks. There is a fair market for 1-1/4" threaded tailpieces that extend lavatory wastes to the correct distance for trap connection.

Fittings for tubular brass consist almost entirely of 45 degree ells, 90 degree ells, couplings and tees in 1-1/4" and 1-1/2" sizes-all with slip joint nuts and washers. Strap wrenches are recommended for most work with chrome-plated brass.

PIPE INSULATION

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. Pipe insulation can also help maintain water temperature in the pipelines to avoid letting water run to reach desired hot or cold temperature.

Wrap-on insulation includes fiberglass pipe wrap with a separate vapor-sealing tape, which 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 somewhat 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 which may be subject to condensation. Available in one-gallon cans (which will cover approximately six sq. ft.), this thick coating is applied in layers at least 1/4" thick.

HEATING CABLES

Two types of heating cables are series and self-regulating. While both types of cables have a similar appearance, plug into electrical outlets, and wrap around pipes, the actual functioning and installation techniques are very different.

Series cables' heat 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, you cannot cut it to length yourself. It cannot be overlapped onto itself without burning out, so be sure to purchase the right length.

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

Self-regulating heating 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 a store, and you cut off only what you need. Separate connection kits can be purchased and put together by yourself 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. And both should be used with a ground-fault circuit interrupter (GFCI) with a 30mA trip level.

PIPE-JOINT COMPOUND

When selecting pipe-joint compound, you need to know what the pipe will carry after installation-natural gas, oil, gasoline, water, or any other fluids or gases.

An advantage of commercially prepared pipe joint compound is its ability to seal all joints, yet make disassembly easy, to prevent seizure of parts by rust and corrosion.

Pipe-joint compounds come in 1-oz. tubes up to brush-on cans or 50-gal. drums.

One form of pipe-joint compound is Teflon tape, which comes in rolls; standard widths are 1/4", 1/2" and 3/4", and lengths range from 30' to over 100'.

Special compounds are also available that are fast drying and hard setting.

Certain plastics are attacked by pipe compounds so be sure the compound is specifically recommended for any plastic material it is used with.

FITTINGS

Fittings allow the you to install pipe in the proper place and terminate it at the right spot. Although each kind of pipe requires its own type of fitting, there are similarities among all fittings. Understanding the proper application for each can save you time, material and labor.

There are two basic designations for pipe fittings: male and female. These refer to the threading. Male threading is on the outside and threads into the female threading which is on the inside of the fitting.

Nipples - extend a line or provide proper threading at the right location. Nipples come in diameters ranging from 1/8" to 4" to match standard pipe diameters and in lengths from close (nipples that are threaded on both ends to a point where threads almost join in the center) through 24". Normal size increments are even inches. Long nipples or "cut lengths of pipe," which are threaded on both ends, are available in about 24" lengths, usually increasing in length by 6" increments (30", 36", 42", etc.).

Couplings - connect all standard sizes of pipe. Tight seal with a pipe wrench and pipe-joint compound will waterproof connection.

Bushings - inserted inside a coupling to reduce the size of the pipe. With a coupling, a run of pipe can be reduced a size or two; with a series of bushings, any number of reductions can be made.

Floor Flanges - connect pipe to a wall, floor or any flat surface. Flanges are threaded onto pipe and tightened. This provides a flange rim with four screw holes, making it easy to fasten pipe to a flat surface.

Elbow - change direction of pipe. Most common are 90 degree and 45 degree elbows, which have inside threads on both ends. A street elbow has inside thread on one end and outside thread on the other.

Reducers - reduce pipe size. Bushings screw into a coupling while reducers screw directly onto pipe threads. Some reduce pipe only one size; others can reduce several sizes.

Side-Outlet Elbows - have three-way outlets. Can be used as corner pieces for railings, fences, etc. Also used for pipe connections on corner construction.

Crosses and Tees - available in all sizes and shapes. Most common is straight tee which has three inside threads of the same size which can be used to run three pipes in a "T" shape. Reducing tee has same shape, but two straight ends of the "T" are reduced one size or more.

Four-Way Tee (Side Outlet) - similar to the side-outlet elbow except side outlet runs through the elbow with an opening of the same size on each end. Straight cross has four outlets for pipe of the same size. Side-outlet cross has an opening on the side for a fifth pipe of the same size.

Return Bends and Y Bends - return bends are made in close, medium and open patterns. The close is a sharper bend than the medium and the medium is a sharper bend than the open. The Y bend is a straight or reduced outlet which permits connecting pipe of the same or reduced size to a 45 degree angle.

Ground Joint Union - three-part fitting that connects any standard size pipe where it may be necessary to disconnect later. Because of the bronze-to-bronze or bronze-to-iron ground-joint seat, it can be taken apart and reassembled at the nut with a pipe wrench and no pipe-joint compound.

COPPER-PIPE FITTINGS

Fittings for copper pipe must be soldered on at least one end, leaving one or both ends unthreaded. After flux has been applied, solder is introduced at the edge of the fitting. It is then drawn, by capillary action, the full depth of the fitting to completely surround the tube.

The result is a strong, leak-proof, bonded joint. The solder is usually applied with a propane torch, a process known as "sweating" fittings.

Appliances that use a small amount of water, such as evaporative coolers and humidifiers, use a small size slip joint tee and saddle tee. A slip-joint tee is installed by cutting the line and spreading it slightly. The saddle tee clamps onto the line and a hole is drilled in the pipe through the side opening.

A commonly used fitting in installing dishwashers is the three-way compression stop. This fitting, installed on the hot or cold sink supply line, will cut the flow of water to both appliances at the same time.

PLASTIC-PIPE FITTINGS

Plastic fittings for plastic pipe, metal fittings for plastic pipe and fittings for connecting (transmitting) plastic to metal pipe are available in threaded, insert, compression and solvent weldable types.

Threaded plastic fittings thread exactly like metal fittings; however, special transition fittings should be used to connect plastic to metal pipe in hot and cold water systems to prevent leaks caused by the different expansion rates of plastic and metals.

Insert fittings are sometimes used with flexible plastic pipe such as polyethylene. Insert fittings are inserted into the pipe and sealed with an adjustable clamp.

Solvent-weld fittings have specially formed sockets into which plastic pipe is inserted. Fitting and pipe are bonded by a chemical weld using the solvent or cement compatible with the type of plastic being connected.

Manufacturer's recommendations should be followed in making such joints. When done properly, these joints form a permanent weld stronger than the pipe itself.

INSTANT-CONNECT FITTINGS

Instant connect fittings make it easy for you to join tubing or pipe. The homeowner inserts the tubing or pipe into the fitting until it seats then pulls back to ensure a tight fit. These fittings are tested up to 600 psi and come in a full range of types to connect copper, polybuty-lene, CPVC and galvanized pipe in 3/8", 1/2" and 5/8" outside diameter. The fittings are easy to use; but once in position and seated, the fitting cannot be removed for realignment.

SOLDER AND FLUX

Solder is used to "sweat" copper and brass fittings; it forms a bonded joint between fitting and pipe.

The specified material for sweat soldering used to be 50/50 (50% lead and 50% tin by weight) or 60/40 (60 % lead and 40 percent tin by weight). However, in 1986 the U.S. Congress banned the use of lead containing materials in public water supply systems and in any plumbing providing drinking water connected to public water systems. As specified by law, all of the States prohibited the use of lead-containing materials in the repair or construction of public water-supply systems. The major U.S. plumbing codes were revised to exclude the use of materials containing lead from potable-water applications.

Among the materials prohibited by law in public water systems is lead solder and flux, defined as those containing more than 0.2 percent lead. In 1986 Congress amended the Federal Hazardous Substance Act, defining lead solder as a hazardous substance. The law requires manufacturers to place warning labels on packages of lead solder introduced into interstate commerce.

Now the specified materials for sweat soldering are "lead-free" solid-wire solders. Lead-free solders contain no more than 0.2% lead. There are a number of lead-free solders available, including 95/5 tin-antimony or tin-silver solders. The first number denotes the percentage of tin. Most of these lead-free solders are formulated by the manufacturers to approach or equal the ease of its application and performance of the traditional lead solder.

Flux (liquid or paste) is necessary for anyone buying sweat fittings. So is a small brush to apply the flux. As with solders, fluxes utilized in the soldering of potable water piping must be lead free.

Used along with solder, flux prevents oxidation of metals as they are heated. It also chemically cleans the surface of items to be soldered after they have been rubbed clean with sanding paper or a wire brush.

By preventing oxidation, flux allows solder to flow freely, forming a good bond.

MAPP GAS

To get a good sweat fitting there should be no water in the pipeline; some homeowners find it difficult to thoroughly drain the line.

This may cause a problem if you are using a propane torch which does not generate enough heat to dry out the line. MAPP gas, however, reaches a much higher heat that can dry out small amounts of water.

Because of this intense heat, MAPP gas must be used carefully, it can melt the copper if held too long in one spot.

VALVES

METAL VALVES

Valves, sill cocks and faucets control the water supply. Valves and sill cocks are used on pipe lines; faucets are installed on fixtures.

Valves in home plumbing lines usually are cast bronze and have portions machined and threaded for trimmings.

Gate valves have a sliding wedge that is moved across the waterway, usually by a threaded spindle or stem. It is either rising or non-rising, the latter having a shorter bonnet.

A gate valve is used to completely shut off or open a waterway, but not control the volume of flow. Either opening of a gate valve may face the pressure side of the line.

Gate valves allow complete passage of water and should be used on supply lines that are in constant use.

Globe and angle valves are used when a valve must be opened and closed frequently under high water pressure. Globe valves are used to control volume of flow. They have two chambers with a partition between them for passage of water which must change course several times from port to port. Globe valves should not be used in water supply lines for occasional shutoff purposes.

An angle valve is similar to a globe valve, but has its ports at right angles. Water passage is greater than through a globe valve; since there is only one change in direction of flow, less resistance occurs. An angle valve installed at a turn in piping eliminates the necessity of an elbow and is often preferred to using a globe valve and elbow.

Plug and key valves are better known as straight stops. These have tapered ground plugs that seat into matched tapered ground bodies. Plugs have flat heads, square heads or socket heads; the other end is threaded to hold a hex nut and friction-ring combination. This is mounted over a tension spring inside the body that keeps the plug tight.

They are manufactured in brass, bronze, galvanized iron-bodied and black iron-bodied and are used mostly as gas stops.

Drainable valves or stop and waste valves have a small opening on the non-pressure side to allow drainage when it is in cutoff position. It is sometimes called a bleeder valve and may be obtained in threaded, sweat, flare and slip-joint ends. The latter two are municipal and emergency valves. Most are flat head or socket head; common residential types have socket head that takes 3/8" key rod.

Check valves operate automatically, permitting flow in one direction only. They are sometimes combined with a throttling or shutoff valve. Some communities require a check valve in cold water lines between the water heater and meter.

Check valves are used to prevent water pumped to an overhead tank from flowing back when the pump stops. Some check valves are designed for use with vertical pipes only. Therefore, correct installation is essential. The closing device-a disk, ball or clapper-falls shut by gravity when installed vertically.

Swing-type check valves serve the same purpose as check valves. A small, smooth swing-type gate is located in the center of valve. As water is pumped through the flow side of valve, the gate swings open to allow passage of water. If water attempts to back up through the valve, the gate is forced shut against the pressure side of the valve.

PLASTIC VALVES

Plastic valves are made of CPVC, PVC and ACETAL. The plastic valves available are gate valves, universal-line valves, straight-supply valves, angle-supply valves, washer-hose valves, angle valves and sill cocks.

One type is molded of ACETAL plastic and has threaded connections for use in metal-piping systems. The other type, molded of CPVC or PVC plastic, is either threaded or non-threaded and has solvent-weld connections. These are used in plastic piping systems. However, PVC gate valves and ball valves can be purchased both threaded and non-threaded

Like plastic pipe fittings, solvent-weld valves (connections made by cement) must be used with compatible plastic-piping systems; i.e. PVC valves used in a PVC piping system.

Threaded-connection ACETAL valves, which can be used in most applications in which metal valves are used, are available in globe (stop), stop and waste, boiler drain, sill cock and sink faucet. Plastic valves should not be used in steam, gas or compressed air lines. However, valves can be used with hot- and cold-fluid systems.

The ACETAL valves perform at temperatures of -20 degrees F to 180 degrees F. They can withstand pressure up to 150 lbs. and are excellent for hard-water areas because they resist mineral buildup.

Since handles are made of plastic, heat is never absorbed from the water line. No brute force is required to install them. Because the threads are more precise than machined threads on a metal part, the installer can mate the parts one to two threads beyond normal makeup on a metal joint for a better connection.

A "double seal" feature allows the washer to be removed, leaving the plastic seat to maintain the integrity of valve. If there is danger of the washer or metal parts deteriorating, it is recommended that installation be made without the washer.

Solvent-weld CPVC and PVC valves offer similar benefits to the ACETAL valves. These are available in globe (stop) and boiler drains. Gate valves and ball valves are available in PVC and CPVC.

When using a plastic valve as a retrofit with another piping material, it is best to use a transitional connector to prevent leaks caused by the differing contraction/expansion characteristics of the two materials.

Newer CPVC valves make a mechanical connection to plastic or metal material. The mechanical valves are easily installed and result in a leak-free connection. There is no solvent welding, sweat soldering or pipe threading; the mechanical coupling on the CPVC valve is loosened, pushed on and hand tightened.


Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.


BACK TO LEARNING GUIDES