f we were successful in communicating the big picture concerning the concept of an overall plumbing system in our first section, you should have a pretty good grasp of the key role played by the piping components. We made the point that if there is any one "most basic aspect" of the system, it is the series of conduits that carry fresh water to, and waste water away from, the points of usage. This second segment is the first of several sections that will deal with the specifics of piping. For openers, let's examine the subject of supply pipingóspecifically, the steel and copper variety.

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Obviously, there's a whole lot more that we require of a supply piping system than just bringing fresh water to us, or we could simply string together a series of garden hoses to meet our needs. Here are some of the additional considerations and requirements:

POTABILITY (pronounced "poat"-ability): In plain English, this means "safe to drink from." NSF (the National Sanitation Foundation) plays a key role in this by determining which materials are safe, and which might be harmful from the standpoint of releasing chemicals into the passing water. Local plumbing codes also govern this area tightly, approving only the installation of those piping materials that have been certified as safe, based on NSF standards. Non-approved materials can be used for those installations in which potability is not a consideration (irrigation, sprinkling, for example).

STRENGTH: We call this bursting pressure or psi (pounds per square inch) rating. In other words, the piping material we use must be strong enough, not only to withstand the pressure of water being supplied from the municipal or private water system, but also to handle periodic shocks at several times the normal pressure. These shocks are commonly called "water hammer," a phenomenon related to quick shut-off valving devices.

While there are a number of significant differences involved in the various types and grades of piping materials available today, there are also some common factors that apply to all. One of these common areas has to do with the terminology used, and since these terms will be used frequently throughout the next several lessons, we want to define them right here at the start: I.D. Inside Diameter—the distance across the inside opening of a section of pipe or tube. O.D. Outside Diameter—the distance across the outside of a section of pipe or tube. Wall—the dimensional thickness of the pipe or tube material only t is important to understand these terms, and the concept behind them, since sizing is often cataloged or specified by just one or two of these factors, and if you need to know one of the other factors, you can deduce the answer from one of the variations of this formula: I.D. + 2 Walls = O.D. O.D. – I.D. ÷ 2 = Wall Thickness (always remember there are two wall thicknesses) O.D. – 2 Walls = I.D. What's The Plural Of "Pipe?"—The proper word for more than one pipe is the same word—"pipe."

SIZE AND CAPACITY: The size of piping used in a given installation is important from the standpoint of delivering the needed amount of water to the points of outlet. Piping that is too small for the supply pressure available deliver inadequate flow (take too long to provide the water desired), but can be objectionably noisy as well. When water flow is restricted, pressure is converted to velocity, which results in noise.

Proper sizing of pipe is a rather complex matter, since the pressure can be affected by the number of outlets being served (and how often they are used at the same time), the distance the piping must travel to those outlets, and the number of turns in the piping. Distance, turns and restrictions in a piping system all have a negative effect on delivery capability, since they all produce friction. This phenomenon is commonly referred to as "pressure loss" or "pressure drop."

RESISTANCE TO CORROSION AND SCALING: It is not uncommon that water that is most suitable for drinking can also be the hardest on the piping system that transmits it. For this reason, the resistance of the piping material to corrosion and scale (accumulated minerals) buildup can be an important consideration.

TEMPERATURE CHARACTERISTICS: There are piping materials available today that are suitable in respect to all of the above considerationsóas long as they are used in transmitting cold water only. Used with hot water, however, they lose some of their desired properties (commonly strength), and become unsuitable. Of the materials typically used for residential supply piping today, temperature considerations are particularly important with plastic piping. Some varieties of plastic pipe are recommended for hot and cold water applications; others for cold water only.

Now that we've taken a look at what to consider in specifying supply piping in general, let's step closer and examine the specific materials commonly used in plumbing systems today. We can identify the following four categories: steel, copper, plastic, and "all others." We'll commence our coverage of the specifics in this section with an in-depth look at the first two categories of supply piping: steel (page 21) and copper (page 26).

If any one of the various piping materials could claim to be "best known to the public," steel pipe would probably be it. Traditionally, when most people think of pipe, the image that comes to mind is the threaded steel type. Although this stereotype has changed somewhat during recent years with the increased use of other materials, steel is still strongly identified in most people's minds as "what pipe is."

Even with this identification, there remains considerable confusion concerning what steel pipe really isóor perhaps we should say, what it isn't.To many people, any pipe that can be threaded is steel pipe. Not true. Then, within our industry, we have the common term "IPS," meaning "iron pipe size." Well, if you have something called iron pipe size, does that mean that there is something called iron pipe? Yes. And since we refer to the dimensions and threads used on steel pipe as "IPS," does that mean that steel pipe and iron pipe are really the same thing? No.

Reading Measurements in Inches Not everyone understands what they are looking at when they see inches expressed in decimals.With the increasing use of the metric system these days, there might be a tendency to think that this is what we mean when we say that a dimension is .500 in diameter, for instance. That isn't the case. For close measurements where fractions would be cumbersome, our English system actually becomes something of a hybrid, in that the inch is divided into 1,000 parts.Thus, when we say that a pipe has a diameter of .500, we mean one-half of an inch. Similarly, .750 is equivalent to 3/4"—.125 1/8" etc. If you remember how to convert fractions to percentages, you can get your equivalents this way. Otherwise, equivalent charts are commonly available.

Here's how all this confusion evolved. Back in the early days of plumbing in this country, most of the pipe made for water supply purposes was wrought ironómore commonly referred to as just plain "iron pipe." It was during this era, around 1862 to be exact, that a man named Robert Briggs took the lead and established some sizing standards for the pipe manufacturing industry. Up to that point, each manufacturer produced pipe according to its own sizing and thread system, which made the matter of interchanging parts in the field a little less than fun. Briggs' system of standardization continues to this day as the basis of the specifications for pipe size and thread dimensions published by the American National Standards Institute (ANSI).

Since the original sizing standards were formulated, steel, brass and certain other specialty materials have come along, all using the same system of dimensions and threads.The strong growth in the usage of steel pipe especially, spelled the demise of the widespread use of the wrought iron variety, so that today, ironically, the material that inspired the original name for the standards is no longer much of a factor in the business.

With the advent of other materials sharing the same dimensions and thread specifications as wrought iron, ANSI adjusted to the times, creating a heading called "Welded and Seamless Wrought Steel Pipe" to cover its tables on pipe dimensions. ANSI developed an even broader heading for thread specifications, relating the standards to "all pipe of steel, wrought iron or brass." Bringing all this up-to-date was a good move on ANSI's part, for it ended the specific identification of the standards with wrought iron, and broadened the application to include the other common threaded types used today.

Old habits are hard to break, though, and back here on the home front in the plumbing industry, the old term "iron pipe" is still going strong. Not only is it common to our conversation, but it is perpetuated by manufacturer catalogs that refer to "i.p." connections.While I really don't think our national security is threatened by the misuse of this term today, it does, along with other industry quirks, make learning the business a confusing challenge for most people.

To try to summarize this fascinating bit of industry folklore then, let's say this:

"Steel pipe is the same as iron pipe only in the sense that they share a common system of sizing and threads. In material makeup, they are not the same."

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More than 100 years of widespread use in this country is an indication that steel pipe must have something going for it. For some specific attributes, here are the claims made for it by steel pipe manufacturers:

1. Strength and ruggedness. It is not easily crushed or damaged by rough handling. It resists both shocks and stress.
2. Engineered to withstand critical service. In burst strength, it can handle the pressure and shock factors of the average plumbing system many times over.
3. Dimensional stability at hightemperatures. Properties of the material and security of the joint remain intact when high temperatures are involved. Steel pipe is especially suited for fire protection service because of its high melting point (2,786∞F).
4. It permits a threaded system of connection that is strong, yet allows disassembly when necessary.
5. It can be butt welded (two ends brought together and welded around the seam).
6. It insulates the sound of passingwater, for quiet service.

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   It is low-cost and long-lasting.

Though there are at least 10 different methods used in producing steel pipe today, by far the largest percentage of production falls into three categories: continuous-weld, electric-resistance-weld, and seamless. The first two types are made with a fused seam along their entire lengths. Seamless pipe has no such weld. Let's take a brief look at the process used to manufacture each:

CONTINUOUS-WELD: This process begins with a coil of flat steel, called the "skelp." The operation is begun by inserting the lead end of the skelp into a super-heated furnace, where it engages with successive sets of rollers. From that point, the coil of skelp is pulled through the furnace, which brings its temperature up to an optimum welding level. The sets of rollers gradually transform the ribbon of skelp from a flat shape to round.

By the time the material reaches a temperature of approximately 2,500∞F., it arrives at the critical set of rollers in the sequence, the ones that actually accomplish the welding operation. These rollers butt the two edges of the skelp together to obtain a good, strong weld joint. No metal is added in this process; it is simply a matter of the basic metal flowing together and bonding at the seam.The last rollers in the process reduce the diameter and wall thickness of the pipe, and bring it to its finished diameter. Then, a rotary hot saw cuts the pipe into desired lengths, normally the standard 21 feet. Next, conveyors move the pipe to a cooling rack, then to a descaler and sizing mill where loose scale is removed and the final sizing operation is made. After cooling, the pipe is straightened, ends are faced and reamed (machined to smooth surfaces), and the pipe is hydrostatically tested (testing in which both ends of the pipe are sealed shut, and high pressure applied to check for possible leaks).

ELECTRIC-RESISTANCE-WELD (ERW): While the end result may be quite similar, the process for welding pipe electrically is very different than what we have just described. There is no furnace involved in producing ERW pipe. As in the case of continuous-weld, you begin with a coil of flat steel, the skelp, but you cold-form it into a round shape on rollers, and then use electrical current to heat the edges into a weld joint.

In a typical operation, after the skelp has been formed into a tubular shape, the material is fed directly into the welding section, which consists of two forged copper discs or wheels, positioned side–by–side (but not touching). These revolving discs serve as welding electrodes, making contact with the steel on each side of the open seam. This results in a flow of current across the seam, raising the temperature at the edges to about 2,600∞F., ideal for effective welding. At the same time, forming rollers on the side exert sufficient pressure on the seam to produce a forging or pressure weld. A small amount of steel material (called "flash") is extruded (squeezed out) during the process, and is removed by cutters as the pipe moves forward past the welding station. Finally, ERW pipe is sent through a series of finishing operations for straightening, facing, reaming and marking.

SEAMLESS: The process involved here is entirely different from that used for manufacturing either of the welded varieties of steel pipe. In this case, you begin with a solid, cylindrical piece of steel called the "billet," or "tube round." The first step is to peel off the outside layer of the billet on a lathe-like device, to assure a good outside finish on the pipe. Next, the billet is heated in a furnace to about 2,300∞F. While at this temperature, one end of the billet is punched or drilled at the center.The billet is then fed between two barrel-like rollers that are positioned at slightly opposing angles to each other. These form the billet into an oval shape, while at the same time rotating it as it moves through the furnace.

This action results in a phenomenon whereby a rough cavity is formed in the center. As the white-hot material moves between the rollers, it next engages with a mandrel (center forming pin), that enlarges and straightens the cavity. So far, we have a relatively short, fat piece of pipe with thick walls.

Next we move our material (still hot) to a plug rolling mill, where a slight reduction in outside diameter and wall thickness takes place, further elongating the pipe. From there, the material is sent through a series of rollers that turn at progressively faster rates of speed to stretch the length and reduce the diameter. As an example, a section of pipe that begins with an outside diameter of 6-3/16", 42 feet in length, emerges from the mill at 2-3/8", 140 feet.

As with the welded types, there are various finishing operations involved, such as straightening, beveling (cutting the end profile of the pipe on an angle), threading and marking. Each furnished in "random" lengths only, as well as in lengths that are cut to order at the mill.

WHICH IS BEST? There are plusses and minuses involved with each of the methods described. Whenever there is a weld involved in metal, there is the potential for a defect. Numerous piping codes recognize this by assigning what they call "reduced longitudinal weld joint efficiency factors." (Try that one out on your friends.) The ANSI Power Piping Code, for example, assigns a factor of 1.00 for seamless pipe, meaning every part of the wall has the same level of efficiencyó100%. Electric resistance-welded pipe, on the other hand, is rated at 0.85, meaning that the weld is rated at only 85% of the strength of the steel walls themselves. And finally, continuous-weld piping is rated at 0.60óthe weld being rated at 60% of the strength of the walls. On the other hand, this standard assumes a perfectly consistent wall thickness on the part of the seamless type, which isn't always the case.

Overall, this whole discussion is really a case of "how high is up?" Continuous-weld piping, considered least efficient in strength by the ANSI standard, is produced at a rate of about 250,000 + miles of material each year, and the number of reported problems is negligible. Think of it this way: Unless you are specifying the pipe for an extremely critical industrial application involving extremely high pressures and/or temperatures, you can be confident using any of the three types. If the least efficient type will withstand pressures of several hundred psi, and the installation you are involved with has a water supply with a pressure of 50 psi (the average), you really don't have much to worry about either way.

FINISHES AND COATINGS: In its natural form, conventional steel pipe will corrodeórust. To protect against this, a process called "galvanizing" is used on a large portion of the pipe produced today. Galvanizing, which has been used for more than 200 years, protects steel pipe in two ways. First, a hot dip zinc coating keeps corrosive moisture away from the underlying steel. Secondly, the steel is also protected from corrosion through a galvanic (minute electrical) action between the zinc and the steel.

Galvanized pipe is easily identified through its characteristic grey color. Unfinished steel pipe (not galvanized) is black in color, and should not be used for plumbing supply piping applications because of its lack of corrosion resistance. To inhibit the formation of rust on unfinished pipe, mills spray the outside surface with a varnish-type oil coating. This protects the pipe during transportation and initial storage. Such non-galvanized pipe is used in "non-water" applications in which fluids and gasses used do not cause corrosion

Though steel pipe can be butt welded for numerous industrial applications, the most common approach used in joining this material is that of threaded connections. In other words, external threads are cut onto the ends of each pipe section, to mate with, or "screw into," internal threads of the mating pipe fittings. It's a system we're all familiar withóevery component in the piping system is threaded with its adjoining members. But while every pipe fitting is furnished with threads already in place, the sections of pipe must be cut to length and threaded as needed during the installation procedure. (The one exception to this is the category of pipe "nipples," short sections of pipe pre-cut to specified lengths, and threaded by the manufacturer.) This is how pipe is prepared for assembly. (Note: there are both manual and motorized versions of the tools described.)

CUTTING: After determiningthe length of steel pipe required, the installerclamps the length from which he will cut his desired section into a pipe vice.A tool called a pipe cutter is used for this.It has two rollers and a cutting wheel that clamp over the pipe. As the device is revolved around the pipe, the cutting wheel cuts into the surface. After each revolution, the handle is tightened more, causing the cutting wheel to dig even deeper, until the pipe is completely severed.

REAMING: Cutting a section of pipe raises ridges of material at the end called "burrs." These are always removed, since they could interfere with the thread cutting, with the smooth flow of water, or possibly break loose later and cause problems to some mechanical device in the plumbing system. Reaming is the step used to remove burrs, and is accomplished by use of a special conical-shaped tool.

THREADING: The key tool components in this case are the die stock, and the specific dies for the pipe size involved. (Think of this as a holder, and the cutters it holds.) The installer must be certain that the dies mounted in the die stock are the ones for the pipe size he is working on, since each size requires either a different set of dies, or a different position of the dies in the die stock.

To cut the threads, the larger opening of the die cutters is placed over the end of the pipe and slowly revolved (some manual units have rigid handles, some have the ratcheting type). The hard cuttingteeth of the dies cut and remove material from the pipe, leaving threads in their path. Oil is spread on the cutting surface to reduce friction during the process.

ASSEMBLY: In making what is called "screwed joints," it is essential to use a good joint sealant on the threads (threads by themselves will not form a perfect seal.)

The sealant serves two important purposes:

1. It lubricates the mating parts to facilitate the tightening, and
2. It forms a seal to assure a tight connection that won't leak.

In addition to compounds that are brushed on (commonly called "pipe dope"), there is also lightweight tape (usually Teflon) that can be wrapped around the threads to accomplish the same thing. In applying compound or tape, it is always applied to the male component of any connection (in this case, the pipe end), since there would be more danger of the material breaking loose and

It may not be obvious at a glance, but the threads used for most U.S. plumbing are tapered 1/16th of an inch-per-inch, to be exact. (In comparison, Europe more commonly uses straight thread.)

Not all pipe threads are the same, either in terms of the number cut per inch, or in the depth to which they are cut. In other words, these are the factors that vary with the size of the pipe involved. It isn't so important to know the mathematics of the various thread depths on pipe sizes, but the

For all but the smallest and largest sizes of steel pipe today, there are three common weight classes available. In plain language, weight class refers specifically to the thickness of wall used. The three classes are: Standard, Extra Strong, and Double Extra Strong. Industry accepted abbreviations for these are: STD, XS, XXS.

You will note from the comparative illustration that the walls get thicker toward the inside, rather than toward the outside.This means that, while you are getting yourself a stronger pipe by going to one of the heavier grades, you are also reducing its capacity.

This factor must be kept in mind when designing systems. In order to achieve the strength and capacity desired for the installation, it may be necessary to go to a larger nominal size. Generally, these heavier weights come into play in rather severe industrial applications, and rarely would anything but the standard weight be required for the average plumbing system.

One further word to assure clear communications: the piping industry refers to these heavier weights as "extra strong" and "double extra strong." You will often hear the term "extra heavy," and while most people would understand this to be the same thing, it's always a

What's a "nominal" size? Usually, when we use the word "nominal" in our conversation, we mean "in name only"óyou can't take what is being stated literally. That's a good way to think of the term, "nominal pipe sizes." Originally, pipe sizes were identified by their approximate inside diameters, and the system came close to having a logical basis. In other words, the nominal and actual sizes of the pipe in question were approximately the same.

But as technology evolved, and the piping industry learned to make strong pipe with thinner walls, the old sizing system became less-and-less a literal guide to identification. As an example,1/2" nominal standard weight steel pipe is made today with an outside diameter of .840, and an inside diameter of .622 (about 5/8").

People who don't understand this are often tempted to choose pipe by its actual size. As an example, if a person thought the pipe size referred to the outside diameter, he would most likely choose one that comes the closest, which would be 1/4" instead. True, you do determine pipe size by checking the outside diameter, but you have to understand that this dimension must be translated from the actual to the nominal.

There is an exception to this:When you get to the extremely large sizes of pipe, 14" through 24", sizes are designated according to the actual outside diameter.

Since all this is a bit much to commit to memory, we have included pipe size information

Even though copper material is used in what we call "piping systems," we don't call it "copper pipe" óthe proper term is "copper tube." A quick definition here will help clarify this matter: metal pipe is generally classified as material that can be threaded (though it can also be welded), whereas tube is material that is joined by means other than threading.You can't say there's no such thing as "copper pipe," however, because there is.Though its use is not nearly as common as copper tube, there is a thicker wall version that can be threaded, and is properly called "pipe." In this section we will be concerning ourselves with the more widely used copper tube. Incidentally, this is another term used for both singular and plural referenceótwo or more sections of copper tube are simply called "copper tube" (not "tubes").

In terms of widespread acceptance and usage, copper tube is newer to the scene than steel pipe, but it has been around considerably longer than most of the plastic varieties we'll be covering in our next section. The greatest period of growth for this piping concept has occurred within the last 50 years, and though local codes and practices vary from one area to another, copper has captured a major share of the supply piping market in this country.

Unlike steel, which is an alloy of iron and carbon, copper tube is made from virtually one mineralócopper itself.All tube made to the standards of ASTM (the American Society for Testing Materials) must contain a minimum of 99.9% pure copper. Copper used in such applications is deoxidized with phosphorus to assure resistance to corrosion, and is technically referred to as Copper No. 122, or DHP Copper.

Manufacturers of copper tube give several reasons for the success and popularity of this material:

1. Resists corrosion and scaling.
2. Lightweight. Installers can carry and handle long lengths with ease.
3. Easily bent and formed. Can be curved around corners and obstructions without need for elbows in many cases.
4. Compact. Requires less space.
5. Easy to join.Versatile system, can be joined using a number of methods.
6. Coils provide longer lengths to make long runs without need of couplings.
7. Ductility (stretchability). Can often withstand the expansion of frozen water without bursting.

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   Saves on labor.

It is considerably easier to explain the manufacture of copper tube than steel pipe, since there is one common method used among manufacturers today, and one finishóthe copper exterior itself.

Copper tube commonly used in plumbing applications is a seamless material, made through a process somewhat similar to the one we covered in our explanation of seamless steel pipe. In the case of copper, you begin with a super-heated cylinder of copper, called the "billet." After one end is pierced or punched to provide a center opening, the billet is forced through an extrusion press that shapes it into a relatively "short, fat tube" with heavy walls. From here, the material is put through a series of reducing dies and mandrels in what is called the "drawing process." This results in the diameter becoming smaller, the walls becoming thinner, and the length increasing.The material is sent through as many of these reducing dies as necessary to bring it to its final, specified size.

Next, if the tube is to be the "soft" type (bendable), it is sent to an annealing oven, where the stresses created through the drawing process are relaxed through heating the material. If the tube is to be the "hard" (non-bendable) type, it is not subjected to this annealing stage. Finally, the tube is finished by operations involving straightening, cutting to length, coiling

Copper tube is one of the most versatile piping systems available today from the standpoint of the methods of connection possible. Among the possibilities are butt welding, soldering and brazing, flare and compressionconnections. By far the most common approach, however, is the soldering method, better known to the trade as "sweat"

As in the case of steel pipe, you are dealing with a "male-female" relation of parts here, the difference being that with copper tube there are no threads involved. Instead of threads, the thing that bonds the mating components together is an external substance called "solder." The once dominant 50/50 compound of tin and lead, has been replaced with different alloys in many instances today, due to regulations that prohibit exposure of water to lead. These other options, categorized as "lead free," include various combinations of tin, antimony, silver, copper and bismuth. Soldered joints depend on the existence of a slight gap between the pipe and the mating socket of the fitting to permit the free flow of molten material between surfaces for a good overall bond. The tendency of heated solder to move into such a gap is called "capillary action." Contrary to what might seem logical, an overly tight "interference fit" between the tube end and the fitting is not desirable.There should be a .004 to .010 clearance between the two diameters to permit a good capillary movement of the solder. Here are the specific steps involved in making a good solder joint:

1. CUTTING: Using a cutting tool similar in basic design to the one used on pipe, the tube is cut to the desired length.
2. REAMING:The burr that has been raised around the inside of the tube is removed.
3. CLEANING: Surfaces to be joined must be free of all dirt, oil and corrosion. The end of the tube is cleaned to a point slightly beyond the area to be soldered, using a fine sand cloth or wire brush.
4. FLUXING: The surfaces to be joined are now covered with a thin film of flux, either liquid or paste.The flux acts as a cleaning and wetting agent to assist in the uniform spreading of the solder over the surfaces involved.
5. ASSEMBLING: in inserting the tube into the fitting, a slight twist will assure an even spreading of the flux on the mating surfaces.
6. APPLYING HEAT AND SOLDER: Using flame from a torch, the material in the vicinity of the joint is evenly heated. When the temperature of the parts is hot enough to melt the solder, the flame is withdrawn, allowing the hot metal itself to melt the solder, which now draws into the crack between the two parts.
7. COOLING: As the joint cools, the solder returns to a solid state, forming the bond

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   between the tube and fitting.

Simply put, brazing is a high-heat version of the basic soldering process, and produces a stronger bond in cases where pressure and/or temperature requirements are more severe.

Actually, there's more involved in the brazing process than just a higher heat the external metal used is different as well. Instead of using a solder compound, brazed connections use an alloy containing a sizeable percentage of silver or phosphorus. Such alloys are called "filler metals," and require torch temperatures in the range of 1,100∞F. to 1,500∞F. to flow. Often, the terms "silver solder" or "hard solder" are used in reference to brazing, but technically, brazing is brazing, and the external

Whereas soldering and brazing are thermal bonding processes, flared joints provide a mechanical connection between copper tubing and relaxed fittings.

Essentially, the concept here is one of forming a slight flange or lip at the end of the tube that allows a nut (inserted onto the tube before flaring) to seal and secure the open end of the tube against the mating face of a fitting. This is where the characteristic of formability of copper tube is a strong advantageónot only in permitting the formation of the flare, but in the conforming of the material to the face of the fitting for the creation of a watertight seal.

These are the steps involved in making a flared joint with copper tube:

1. CUTTING AND REAMING: Same steps as in the soldering process.
2. SLIPPING COUPLING NUT OVER TUBE: Important to rememberóyou can't get it on once you've made your flare.
3. FLARING TUBE END: There are two common ways to do thisówith a hammer and "impact pin," or alternatively, with a special screw-type tool.
4. ASSEMBLING THE JOINT: Insert the coupling nut over the male threads of the

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   fitting and tighten until a good seal is obtained.

There is one other common method of joining copper tube today, available only on the smaller sizes. Compression fittings provide perhaps the easiest assembly of all, since they eliminate most of the preparatory steps involved with other systems. Typically, you will see this type of connection made between supply stops and fixtures, such as used on the small diameter tubing that serves ballcocks and faucets.

With this system, a coupling nut is inserted over the tube, as in the case of the flared joint system. But rather than flaring the tube end, the coupling nut is immediately tightened onto the mating male threads of the fitting.This tightening compresses a small ring, called the "ferrule," around the end of the tube, locking it into a depression around the diameter. This process results in a good,

Because copper tube is so readily formable, it is often bent to adapt to the needs of a piping system at the job site. This is a relatively simple matter to do by hand if a wide, sweeping radius is involved, but for tighter bends, it is often desirable to use a special piece of equipment to avoid kinking the line, which would restrict flow. Such tools can range from a simple spring-like device that prevents the collapsing of tube walls, to more sophisticated

In defining the types of copper tube available today, the first area of distinction concerns the temper of the material. In plain language, this means how "bendable" it is. In our explanation of the manufacturing process used to produce copper tube, we mentioned the fact that some tube is annealed after being drawn, while some is not.That's what is behind these two basic terms we use.

When we say "drawn" tube, we mean that it has not been annealed, and therefore remains relatively stiff. This also means that it is furnished only in straight lengths, not in coils.

When we say "annealed," on the other hand, we mean that this tube has been drawn and annealed. The annealing softens the material, making it bendable, and hence, it is available in coil form, as well as in straight lengths.

In common usage, you are likely to hear the terms, "hard tube" and "soft tube"

Like steel pipe, copper tube is available in more than one weight, providing several choices in wall thickness for each nominal size. The selection of type is determined not only by the requirement of the installation, but in some cases, by local code regulations.

Before we give you the specific type designations, we want to point out that there are two principal classes of tube produced today. One is called "plumbing tube," broken down into the four categories that follow, and the other is called "ACR" tube, which stands for air conditioning and refrigeration. Let's take a look at plumbing tube types.

Tube Codes Type Color K Green L Blue M Red DMV Yellow ACR Blue (straight lengths]

For supply piping systems, the common designations for the individual weight categories of copper tube are types "K," "L" and "M." Type "K" is the heaviest of the three (has the thickest walls), while type "M" is the lightest.

In addition to these three types that which are suitable for pressure installations, there is another type that falls within the plumbing class of copper tube, called "DWV." While this section of the course is primarily intended as a coverage of supply piping materials, it would probably be confusing if we separated our coverage of DWV copper from the other types, so for that reason, we have included it on our fold-out chart at the beginning of this article. It is important to understand, however, that Type DWV copper tube is intended for drainage applications only, never for pressure installations. This is due to the fact that, in terms of wall thickness, DWV is lighter than any of the three pressure types of copper tube, "K," "L" and "M."

Since the differences in wall thickness cannot be easily determined simply by looking at the various types of tube, manufacturers help us by identifying each type with a special color code. Hard temper tube (straight lengths) is color-coded right on the material itself, whereas the coiled soft temper tube is identified with color-coded tags.

The nominal system of identification is used on all but Type ACR copper tube today, meaning that you have to know how to translate to exact dimensions. Again, this information is contained in the color table that we have prepared for at the beginning of this section. (Might be a good idea to print this for handy reference.) It is important to remember that, in contrast with plumbing tube,ACR tube sizes are based on actual outside diameter.

As with steel pipe, there are many uses for copper tube beyond water supply applications. Mentioned already are the DWV type for drainage use, and the ACR type for air conditioning and refrigeration usage. Beyond this, there are numerous uses of ACR