or those of you who may be feeling that you have read more about supply piping in the past two sections than you ever wanted to know, here’s a breather. Instead of looking at pipe itself this month, we’re going to cover the things that join those sections of pipe together—the fittings.

This coverage will deal specifically with the types of fittings used in supply (pressure) systems. Although there are many similar configurations of design within the category of drain, waste and vent (DWV) systems, there are enough important differences to warrant a separate coverage of that subject in this next section.

Pipe fittings are designed to do one or more of the following things:

1. Extend or join a pipe line in the same direction.
2. Change the direction of a pipe line.
3. Branch off a pipe line.
4. Close off an opening in a pipe line.
5. Connect pipe sections of different diameters (reduce or enlarge).

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"Section IV takes the complex subject of pipe fittings and strips it down to its most basic common denominators. This "basic training" is elementary, as the subject will be covered in much greater detail later."

Before we get into some specific examples of each of these possibilities, let’s back up a step and look at some of the more general considerations involved in specifying pipe fittings.

The Piping System Involved—The first and most basic thing to determine in fittings specification concerns the piping system in which the fittings are to be used. What is the material used? Steel? Copper? PVC? PEX? Each basic type of piping material has its own unique types of fittings specifically designed for use with that system.

It is important to understand that most types of fittings are not interchangeable between systems. In other words, fittings designed for use with steel piping are not usable with copper tube systems, and vice versa (except in the case of certain “transition” or “adapter” types of fittings, which we’ll cover later).

The Weight Grade: In terms of strength, the fittings used must have a pressure capability equal to the piping material being used. As an example, if the basic piping system involved is “double extra strong steel,” you would want to be certain that the fittings used are strong enough to match the pressure capability of that system. The method of identifying pressure grades of fittings varies from one system to another. With some, the identification is essentially the same as the pipe with which it is used (for plastic piping—Schedule 40, Schedule 80, etc.). With others, the classes are identified according to pressure rating (class 150, class 300, etc.).

The System Of Connection: Once you have determined the basic type and weight grade of the piping system, the next consideration is the means of connection involved. If the system is to be “Type M” copper, for instance, that still doesn’t give you all the information you need in order to specify the fittings. What method of connection will be used? Sweat (soldered or brazed)? Flare? Compression?

Similarly, there are alternate considerations related to the joining of other piping materials. Steel pipe can be welded or screwed, as can several types of plastic piping.

Material Make-Up: The material and process employed to make the fittings is primarily a consideration related to metal piping systems, since many of the plastic piping varieties require the use of a fitting material identical to the piping material itself. In applying this consideration to metal piping, it is important to understand that this subject often goes hand-in-hand with the weight class and pressure criteria already discussed. Many times, when a fitting with a higher-than-normal pressure capability is required, it is necessary to select a different specific fitting material than that which is normally used.

Using a steel piping system as an example, specification of malleable iron rather than cast iron supply fittings automatically means that you are selecting a variety with a greater pressure capability. Then, within the specific category of malleable iron fittings, you would further identify the desired strength according to the pressure classes available (as discussed).

There is a parallel situation in the case of fittings used with copper piping systems. In this instance, you have the option of products made of wrought or cast copper, as well as varieties made of brass and bronze. One of these specific materials would be selected on the basis of the type of copper tube being used, together with the strength requirements involved.

Finishes Or Coatings: Here again, this is a consideration that relates primarily to fittings used with metal piping systems. In the case of fittings used with steel piping, for instance, there is commonly the option of plain (also called “black” or “unfinished”) or galvanized. In addition, certain fittings are sometimes specified with a chrome-plated finish (usually in applications where they would be exposed to view, or where sanitation

Based on what we have just covered in terms of the number of options to consider when specifying fittings, it would clearly require a big, fat book to describe every specific variety available today. (In the business, this is what we call the “geometric explosion syndrome.” If you start out with 100 different models of widgets in your line, and decide you “simply” want to add a left-handed option, you don’t just add one more model to your catalog—you add 100 more. That’s what we’re dealing with here on the subject of pipe fittings.)

With the number of basic configurations, hybrid configurations, connection systems, weight classes, finishes and sizes—all multiplied by each other—there is an astronomical number of individual design possibilities. Our goal in this course is not to assist you in committing 10,000 subtle variations to memory, but rather to simply provide you with a grasp of “what the basic shapes are” —the configurations based on function. From there, you can apply this fundamental understanding to any specific fitting system, and “fine tune” the selection in each case, using other guidelines we’ll give you.

In approaching our explanation of the basic configurations, we’ll use our expanded, five-point definition of pipe fittings as an outline, categorizing the various types of fittings according to function. Keep in mind that not every fitting configuration or combination of options is available within every system of connection; and within systems, not every manufacturer necessarily produces every design indicated here. This is an overview, showing what is used in a total sense. When you get down to the specifics of ordering, you’ll have to rely on the manufacturer’s

Couplings: The coupling is one of the simplest fittings used. In function, it is a sleeve used to join two sections of pipe or tube in a straight, in-line run. Here are the two variations available in this category:

1. Conventional: By far the most common, this is a simple sleeve with a female opening at either end for connecting to the mating pipe ends.
2. Extension Piece: In this case, the fitting has a female opening on one end, with a male connection on the other end.

Nipples: Whereas most fittings are characterized as being basically “female” components to receive male ends of pipe sections, nipples are short “male” pieces used to join with female components. Essentially, nipples are simply short pieces of pipe. Though they can be made up on the job site in the same manner as the basic pipe itself, nipples are commonly furnished in specific lengths, already threaded for installation.

We should qualify that statement, however, by saying that “store bought” nipples are primarily used with threaded piping systems. On the other hand, nipple requirements in copper and non-threaded plastic piping systems are simply met by cutting pieces of tube or pipe to length on the job.

Technically, a nipple is considered to be a piece of pipe that is 12” or less in length. The numerous specific lengths of nipples available fall within three general size categories:

1. Close: This is the easiest to identify, not only because it is the shortest, but because it is the only type with threads across the entire length (threads from both ends meet in the middle).
2. Short (sometimes called “shoulder”): This term covers the intermediate lengths, and has a portion of plain, unthreaded surface between ends.
3. Long: Obviously, this is a longer version than the short, threaded on both ends with an expanse of plain unthreaded surface in between.

The exact lengths within these overall categories vary with each pipe size involved. For example, a close nipple used with a 10” diameter pipe would necessarily have to be longer than one used on 1/2” pipe. In addition to these standard “straight nipple” configurations, there are also types available with a “hex” in the middle to facilitate tightening with a wrench (“hex” is a common industry term referring to a six-sided shape— like a nut—for engaging with a wrench).

Unions: A union is a fitting that is used to permit a quick disconnection in a pipe line, or to make possible the final assembly of components.

Here’s what we mean by the second part of that statement: Let’s say you are making a run with steel pipe from your incoming service line to your water heater, beginning at the shut-off valve just past the water meter. You start by screwing in a length of pipe, and two or three more pipe lengths and fittings later, you are ready to put the final piece in place.This final piece is a long nipple with threads that will mate perfectly with the last fitting assembled, and equally well with the inlet opening of the water heater. But here’s the rub: having right-hand threads on both ends, the nipple cannot screw into both openings at the same time. In other words, screwing one end unscrews the other end. Solution? You guessed it—the union! (You thought maybe we’d suggest rotating the water heater?)

In concept, a union is essentially a coupling that breaks in the middle, with the two ends being joined together by means of a threaded nut. Each end component has a female provision for connecting to a pipe end. The third primary component in a union design is a threaded collar—a nut that draws the two ends together when tightened.

Though there are some unions available that seal against possible leaking by means of a gasket between end components, the more common type is one that seals with a sort of “ball and socket” relationship (these shapes may not be clearly evident at a glance, since their center areas are cut away to form the water passageways). Called a “ground joint,” this design is a little more “forgiving” in cases where sections of pipe being joined may not be perfectly in line with each other. In other words, because you are sealing on spherical surfaces, these unions require a little

Elbows: This is one of the easier pipe fittings to explain, since most people have a handy point of reference half-way down their arms. Also called by the nickname of “ell” or “L,” these fittings provide an angled change in direction of a pipe run.

1. Regular Elbows: Like couplings, regular elbows have two female openings for connection to the adjoining pipe sections. Though there are more gradations of angles available within the category of DWV elbows (to be covered in the next section), in supply elbows, the common angles are 90° and 45°.
2. Street Ells: This variation is different than the regular elbow in that it has a female connection on one end, and a male connection on the other. The advantage of this design is that it can eliminate the need for a nipple in certain cases. For example, if you wanted to angle your piping into the inlet of a valve, you would screw a street ell directly into the valve. Using a regular elbow for this requirement, you would need a nipple to join it to the valve.
3. Drop Ear Ells: These are essentially regular elbows with short flanges (ears) extending f r o m one end of the bend. Holes in the ears are used to secure the fitting to the wall framing, which in turn, makes the pipe run rigid at that point.

Return Bends: Here, we have a “U”-shaped fitting with female connections at both ends (like two 90° elbows stuck together). Return bends are commonly available in three configurations that relate to the radius of the bend itself in each case: Close, Medium and Open. A close return bend has a very tight radius, resulting in positioning the connecting pipe sections extremely close together. At the other extreme, open return bends have a more sweeping radius, which

Tees: This is another fitting that pretty well describes itself. Shaped like the letter “T,” this design has two female connections in line with the primary pipe run, and a third female connection at a right angle out the side. One of the most commonly used fittings, the tee permits the creation of a branch line off a main pipe run.

Wyes: Same basic concept here as the “tee,” except that the side outlet comes off the fitting at a 45° angle, rather than a 90°. In appearance, it looks like the letter “Y” ; hence, the name.

Crosses: These are like “double tees”—they permit the creation of two branch lines off the single fitting that contains four female connections positioned at 90° angles to each other. Here again, the name gives the clue to the shape, with the fitting forming a symmetrical cross pattern.

Plugs: These parts are designed to seal off a female opening in a piping system.An example of this would be a “tee” that is installed with a future branch in mind, but is needed to serve simply as a coupling for the present. In order to seal off the third opening in the “tee,” a plug would be inserted until such time that the branch line is added. Typically, plugs for threaded connections are furnished with a square head or square recess for turning (and the heads on certain larger sizes are sometimes hex shaped).

Caps: These are the female counterparts of plugs. Instead of mating with openings, caps are used to close off male components—pipe ends. An example of this application is the use of short, vertical “deadend” piping runs that tee off water supplies leading to faucets and valves. Acting as shock absorbers “ against water hammer (air trapped in these pipe sections cushions the impact created by valves that shut off abruptly), these risers are sealed at the top with the use of pipe caps. In configuration, some caps are furnished with a square-head protrusion for

In a purely functional sense, the fittings below are the same as those discussed in our first category of fittings: they are used to extend or join a pipe line in the same direction. But unlike those that are used to join pipe sections of the same diameter, these are used to connect pipe sections of different diameters.

• Reducers: This is similar to the coupling in that it has two female connections for joining the related pipe ends. In this case, however, one female opening is always smaller than the other. Available in a variety of “size-to-size” combinations, such fittings are used as transition components when a pipe line changes from a larger diameter to a smaller one.
• Bushings: These fittings are often confused with reducers, and it’s easy to see why. In a sense, both do the same thing: they connect components of different diameters. But here’s the difference: Whereas a reducer has two female connections, the bushing has one male connection (always the larger), and one female connection (always the smaller).

Here’s an example of how a bushing would be used:

Let’s say you have a valve that requires 3/4” IPS connections, but your basic piping system is 1/2” IPS. You take a 3/4” by 1/2” bushing— screw that into the valve. Then, you screw your pipe section into the bushing. If you were to use a reducer to accomplish the same thing, you would need still another component, a close nipple, to connect the reducer to the valve.

Bushings are available in two basic configurations:

1. Hex Bushing: This type has wrench flats on one end, and is used where it is not necessary for the part to be screwed flush with the mating female component.
2. Face Bushing: On this type, the male threads run the entire length of the fitting. It is used where a flush fit is desired.

Most bushings are the “concentric” type, meaning that the smaller opening is in line with the male end (diameters on the same centers). There is a specialty type of bushing called the “eccentric” variety, in which the smaller opening is offset to one side, not in line with the center of

Combinations of Functions: For many of the basic pipe fitting configurations mentioned thus far, there are hybrid variations available that are made possible by combining them with aspects of other fitting designs. (Remember what we said about “geometric explosions”?)

As an example, let’s just start with one of the last designs we mentioned, reducers.This function is applied to many of the other fittings discussed.There are reducing elbows, reducing tees, reducing wyes and reducing crosses.

Similarly, with the union function, you have union elbows and union tees. There are unions with one male connection and one female. And there are elbows and return bends with side outlets (the tee function).

We could go on and on with examples of these combinations, but you get the idea by now—if there is a need to combine functions into a single fitting, chances are that somebody, somewhere, makes exactly what you need. Check it out.

Transition (Adapter) Fittings: With a few exceptions, we haven’t related much of our discussion concerning supply pipe fittings to specific systems of connection.Again, we feel that the most important thing to understand is the function and configuration of each basic fitting design. With that, you can apply the concepts to any specific system and have a pretty good grasp of what you’re dealing with.

But there is one important consideration in regard to the different systems of connection. While it ordinarily isn’t possible to use the fittings from one system to join directly to another, almost all systems include fittings that make the transition. Not too surprisingly, these are called “transition” fittings (also called adapters).

As an example, there are fittings that have female steel pipe threads on one end, and a female copper tube socket on the other. Likewise, there are fittings that join threaded steel to solvent welded pipe, ones that join flexible plastic pipe to threaded steel, compression copper to sweat copper, etc., etc.

Using such fittings, it is possible to use more than one type of piping material in the same over-all system. If you wished to make a plastic pipe branch line off an existing steel one, for instance, you would come off the main run with a steel-to-plastic transition fitting. From that point, all the pipe