Working with Pipe: Intro and Threaded Pipe

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As more kinds of pipe become available, you will need to know what can mix and what can’t. Should you use plastic pipe? Cast iron? Copper? What’s involved in measuring, cutting, bending, joining, and repairing the various kinds of pipe, and what tools will you need for the job?

There are three basic ways to join pipe and fittings to each other. The first and probably the most common is with threaded or screw-together joints. The second is with fused joints, that's , with soldering, welding, brazing, or cementing. And the third is with compression joints, where the end of the pipe and the fitting are pressed together with a threaded nut, but the ends of the pipe aren’t threaded. Flare joints in copper tubing and the connection of the tailpiece to a P-trap are examples.

Iron, brass, and old-fashioned copper pipe in standard or “schedule 40” thickness are almost always connected by threaded joints, Copper tubing and plastic pipe have some threaded fittings, but the pipe itself is almost never threaded. Copper tubing is usually soldered or held together with flare fittings. Plastic pipe is almost always welded to its fittings with solvent cement. PB (polybutylene) plastic tubing is joined with compression fittings; it can't be solvent welded. Thin-walled brass pipe, like the 1¼-inch or larger chrome-plated drain pipe under your sink, is sometimes threaded but usually held together with flexible-ring compression joints. If it's threaded, the threads are very fine and were cut at the factory—you can’t thread this kind of pipe yourself.

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Some Words of Warning

Plumbing and electrical wiring don’t mix. Your plumbing system, especially the metal cold-water pipes, is such a good conductor of electricity that it's used as a ground for your telephone and for all the wiring in your home. Be careful when working with your plumbing not to contact any electrical wiring, metal pull chains, or the like.

Ground connections. Look for an electrical ground connection on any pipes you are working on—it will usually be on a cold-water pipe (see drawing). If you must remove such a connection, replace it immediately on another cold-water pipe or in a different place on the same pipe. If it's a very large wire, it's probably the ground for your main supply panel. It is imperative that it remain attached at all times, Small wires may be from your telephone, washing machine, or another electrical appliance. It isn't so urgent that these remain attached, but the appliance should not be used while the wires are disconnected.

Galvanic action. When two different metals are immersed in water, a weak electric current flows between them. This is called a galvanic current. In plumbing installations, the two metals are usually iron— especially galvanized iron—and copper or brass. As the galvanic current flows from the copper, it carries copper atoms through the water and deposits them on the iron. Over a period of time, the copper pipe and fittings can deteriorate enough to cause leaks.

Ill.25 Ground Connection: Ground clamp, Cold water pipe

If you add copper pipe to an established system of iron pipe (or vice versa) you should put a dielectric fitting between the two unlike metals. These fittings have an insulator that prevents the iron from contacting the copper directly. Another method, preferred by some plumbers, is to install a brass fitting, a coupling or nipple, as an intermediate link between the iron and copper parts of the system. Although dielectric or brass fittings are very helpful, they can't completely prevent a very slight, but unrelenting flow of electricity and copper atoms.

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Old-fashioned thick-walled copper and brass pipe have the same threads and fittings as galvanized steel pipe but are rarely used these days. Copper pipe is no longer available. Brass pipe is available but is so expensive that it's used only in small amounts for decorative purposes or to separate iron pipe from copper tubing to minimize galvanic action when the two metals are used in the same system.

Galvanized steel pipe, usually called iron pipe, has been used in more homes than any other kind. Almost all homes built prior to 1955, and many homes built since then, will have threaded iron pipe throughout. This kind of piping system has been used since before the turn of the century. Although the life span of galvanized iron pipe is usually considered to be 20 to 30 years, many homes built in the early 1900s have iron plumbing systems that are still being used. Most of these, of course, have had some parts of the system repaired or replaced, but many have a good deal of the original system still in service. Its ready availability relatively low cost, and long life span are the main reasons for using iron pipe. Its strength and ability to withstand bumps and pressure make it useful in hostile environments, too.

It also has a couple of drawbacks. Iron rusts. Even though it's galvanized and the threads are covered with pipe compound when it's put together, eventually every system will need to have some sections replaced because they rust out. Another problem is that the relatively rough interior surface and the ridges where pipe and fittings meet—as compared to sweated copper or plastic pipe—cause mineral deposits from hard water to build up, which may eventually block the pipe altogether. The installation of a water softener will sometimes reverse the action, however, as the softened water tends to dissolve the deposits.

If you plan on doing some plumbing yourself, there are other negative attributes of threaded iron pipe. You will need a greater number of tools and a little more skill to work with it, Thick-walled iron is very unforgiving be cause of its rigidity. You will need to be much more ac curate in your measuring and cutting than with the more flexible copper tubing or plastic pipe, If you cut a piece too long, you will have to re-cut and rethread it. If it’s too short, you will have to replace it entirely.

Threaded pipe and fittings of all materials will have standard pipe thread. Whether pipe is threaded at a factory or hardware store or you do it yourself, it will all have the same threads and will always fit with other pipe and fittings of the same diameter, There are only a few places in a plumbing system where you will find any other threads. Thin-walled brass tubing used for sink drains will sometimes have a fine machine thread put on at the factory; compression fittings will have machine threads just like those on nuts and bolts (which is what they are), and faucets will often have the ends threaded to accept a garden hose. Hose thread is a very coarse thread found only on hose and fittings designed to connect to hoses.

Pipe thread is unique in that it's tapered. It is cut at an angle so the thread at the end of the pipe is smaller in diameter than the one a half inch up the pipe. The taper, which is about ¾”/foot, causes the joint to tighten as it's screwed together so it seals the joint.

Ill.26 Iron Pipe Fittings:

  • Reducing coupling
  • Reducing elbow
  • Side-outlet elbow
  • Side-outlet tee
  • Close nipple
  • Nipple
  • Elbow
  • Street elbow
  • Shoulder nipple
  • Tee
  • Street tee
  • Reducing tee
  • Straight coupling
  • Cross
  • Reducing cross
  • Flange
  • Ground union
  • Bushing
  • Side-outlet cross
  • Plug
  • Nut or collar
  • Shoulder piece
  • Cap
  • Extension piece

Pipe and Fittings

Iron pipe and fittings are manufactured in sizes from ¼ to 2½ inches, However, a hardware store or plumbing supply house that caters to homeowners rather than con tractors probably will stock only the ones commonly used in houses: 1/2-, 3/4 and 1-inch and sometimes a limited quantity of 1¼- and 1½-inch pipe and fittings. The 2½-inch size isn't usually stocked but can sometimes be special ordered. The pipe comes in standard lengths of 10 and 20 feet with threaded ends. Many dealers will cut lengths to order and therefore will have shorter lengths on hand if you want them.

Nipples. Originally nipple was a name given to any piece of pipe 6 inches or less in length. Now, however, plumbers and dealers often refer to any precut and threaded lengths of pipe they stock as nipples. Most stores have nipples in lengths of ½-inch increments from 1½ inches to 6 inches and in 1- or 2-inch increments up to 12 inches. Some stores even stock nipples of 18, 24, 30, and 36 inches. A nipple of 1½ inches or less that's threaded for its entire length is called a close nipple. One that has only a small unthreaded section in the middle—¼ to ½ inch or so—is called a shoulder or short nipple. These are obviously used when fittings need to be touching or very close to each other.

Elbows. Also referred to as ells, these are used when the pipe must change direction. They are available in 45- degree and 90-degree angles and in several forms. A standard ell has both ends the same size and both openings are female. A reducing ell has one opening smaller than the other. A street ells female on one end and male on the other.

Tees. These fittings are shaped like a “T” and used when a pipe line branches at a right angle. A straight tee has three female openings, all the same size. The most common reducing tee has run-through openings the same size and the branch opening smaller, but they are manufactured in several combinations of two and three different-sized openings. The drawings show a few of them. A tee with two female openings and one male opening is called a street or service tee.

Crosses. When you want two branches to leave the main line at the same place, you use a cross. A straight cross has all the openings the same size. Reducing crosses come in several combinations of sizes, just like tees.

Side-outlet ells, tees, and crosses. All of these are just like regular ells, tees, and crosses except that they have one additional opening at a right angle to the plane of the others, as shown in the drawings.

Couplings. Couplings are used to join two pieces of pipe without changing the direction. In a straight coupling, both openings are the same size. In a reducing or bell coupling, one opening is smaller than the other. Usually couplings have female openings at both ends. One with a female opening on one end and a male opening at the other is called a reducing piece.

Unions. A union joins two lengths of pipe of the same diameter without changing direction. It is different from a coupling in that a union can be installed and removed without turning either length of pipe. A union is a three-part fitting. The center piece or nut is slipped onto one of the lengths of pipe. Then the two end pieces are screwed onto the two lengths of pipe, using pipe joint com pound—the one without threads must go on the length of pipe that's holding the nut. Line up the pipes, mate the ends of the union, and tighten the nut. The nut will draw the ends of the union tightly together. Use no pipe compound where the ends of the union join, The smooth mating surfaces of the union will seal tightly without it. Unions are generally used where a new branch line is added to an existing system or where an appliance or fixture must be replaced periodically. A water heater, for instance, is usually attached to both the hot- and cold-water pipes with a union.

Bushings. A bushing is usually used to reduce one opening in a tee, elbow, or other fitting so it can accommodate a smaller pipe. It is both male and female; that's , it has threads both inside and outside and is hexagon- shaped on one end so it can be turned with a wrench into the fitting or onto the pipe.

Caps. A cap, or concave piece of galvanized iron with female threads inside, is used to seal the end of a pipe for testing or to make an air chamber. It can also be used to close off a pipe that's no longer in use.

Plugs. A plug is a solid piece of galvanized iron with male threads on the outside and a square head that can be gripped with a wrench. Some plugs have a slot like a screw, but these are rare. A plug is used to close one opening in a fitting when it’s not needed. It can be used along with a coupling to seal the end of a pipe.

How to Join Pipes with a Union

Ill.27 Male thread, piece, Shoulder, piece

1. Screw the male thread piece onto one pipe.

2. Slip the nut over the other piece of pipe and screw on the shoulder piece.

3. Pull the male thread piece and shoulder piece together, slip the nut over the shoulder piece, and screw it to the male thread piece.

Ill.28a 1. Measure the pertinent existing dimensions—between faces of elbows (14’ from centerline of horizontal pipe to the centerline of where the pipe will go through the wall (9”), and from the face of the ell to the other side of the wall (4”).

2. Sketch these dimensions and add other dimensions that will help you select the right fittings and enough pipe.

3. Make a list of what you’ll need to buy.

Ill.28b Vises: Pipe vise; Machinist’s vise with makeshift wooden jaws

Measuring, Cutting, and Threading

Because iron pipe is so inflexible, precise measuring is essential to a neat and efficient job. If you plan to let someone at the hardware store cut your pipe for you, it’s even more critical in order to save running back and forth to the store and to avoid buying a lot of extra pipe.

First sketch out the installation you are planning. It can be quite rough, just clear enough for you to follow, Mark on the sketch the fittings you’ll need. Will you need a union? A tee? How many ells? In order to get accurate measurements, it would be a good idea to go buy at least one of each of the fittings you’ll need and to use them to precisely determine their dimensions and that of the pipe.

For instance, if the new pipe must go from a main line pipe to a wall and then turn and follow the wall, you will need to know how much distance will be taken up by the tee you’ll put in the main line and the elbow at the wall. When measuring the length of the pipe, hold the fitting in place and mark the position of the face of the fitting. Measure the distance between the faces of the fittings and then add the length of the threads that will be inside each fitting. The thread inside the fitting will be almost exactly ½ inch if you are using ½- or ¾-inch pipe; 9/16” for 1” pipe; and 5/8” for 1¼-inch pipe.

You can cut and thread iron pipe at home very easily. You will have to buy a pipe cutter, a reamer, and a set of dies with a holder, also called a stock, with pipe handles to hold and turn the dies. A pipe vise is also a good idea if you are going to do very much cutting. If you are only going to cut and thread a few pieces of pipe, you can usually rent the cutter, reamer, threader, and vise. You can also modify a machinist’s vise to hold the pipe (see drawing). If you only have one or two pieces of pipe to cut and thread, let your local hardware store or pipe supply shop do it for you. As long as your measurements are accurate, this will cost the least in both time and money.

The dies for threading pipe are made of hardened steel teeth that cut the threads into the relatively soft steel of the pipe. Most die sets have cutters for pipe of s/s-, ½-, ¾-, and 1-inch diameters, which are the sizes you’ll need to work on any water or gas supply pipes in your house. If you need 1¼-, 1½-inch, or 2-inch pipe cut and threaded for a drain system, it’s probably best to have it done at the hardware or plumbing supply store.

Make sure the piece of pipe you are going to cut is long enough. Check both ends to be sure the threads aren't damaged. If one end is damaged, make your measurement from the undamaged end or re-cut the threads before you start measuring. Mark the pipe with a sharpened crayon or pencil where you want to cut. Yellow or white shows up best on the gray pipe and makes it less likely you will make an error.

To cut the pipe, put it in your vise with your mark about 6 to 8 inches from the vise, Open the cutter wide enough to clear the diameter of the pipe. Set it on the pipe with the cutting wheel on the mark. Apply cutting oil to the cutting wheel and rollers of your pipe cutter to make the cutting easier and to prolong the life of the wheel. Turn the handle so the wheel bites into the metal just a little bit. Rotate the cutter a full turn around the pipe to make a very shallow cut. Turn the handle a little more and rotate the cutter. Then do it again. You will soon get the knack of how deep to set the cutting wheel each time. Turning the handle too much can break the cutting wheel or spring the frame of the cutter. Once the pipe is cut of f. wipe the end with a rag. Be very careful not to cut yourself on the sharp edge or on any burrs (rough spots). Check the cut for smoothness. Remove the burr around the inside of the pipe with a reamer and smooth any roughness with a file.

You can cut pipe with a hacksaw, but any jagged edge or deviation from a right-angle cut will make threading difficult or impossible. If you must use a hack saw make the cut just as square and smooth as possible and use a file to clean and smooth the end when the cut is completed.

To thread the pipe, insert the proper die in the die-stock. Be sure the pipe is tight in the vise. Slide the die- stock over the end of the pipe and apply pressure with the heel of one hand while you turn the stock slowly. When the die has taken a small bite so it's firmly started, put a lot of cutting oil on the die. Give the stock a complete clockwise turn; then turn it counterclockwise about a quarter turn. Again turn clockwise a full turn and back a quarter turn. This backing off a quarter turn for every full turn you make clears cut metal from the die and burrs from the new threads. Continue cutting in this manner until 1/8 to ¼ inch of the end of the pipe emerges from the diestock. Be sure there is always plenty of cutting oil on the die. When the cutting is finished, back the die of carefully to avoid damaging the new threads. Use a heavy rag to wipe away excess oil and chips.

Ill.29a Cutting Pipe: After the pipe is cut, use a reamer to remove burrs.

Ill.29b Threading Pipe: Replaceable die. Keep the die well covered with oil at all times.

Joining Pipe and Fittings

Most professional plumbers assemble sections of the sys tem they are installing at a workbench when they can. They think it's easier than doing it while lying on their back in a damp, cramped crawl space. You can usually screw at least one fitting to the pipe you just threaded while it's still in the vise. Then screw the assembled pipe and fitting into the last fitting you’ve already installed.

To get a good, leakproof joint, inspect both the male and female threads. Both the pipe and the fitting must be free of rust, burrs, and metal chips. Put joint com pound or Teflon tape on the male threads. Apply it evenly. Do not try to put compound or tape on the female threads, Screw the fitting onto the pipe by hand. It should go on easily for about three or four turns. Then turn it on snugly with pipe wrenches.

When assembling pipe. select wrenches of the proper size for the job. A wrench that’s too small requires too much work, which causes unnecessary strain on your body and can cause slips that take skin from knuckles. A wrench that’s too long may cause you to tighten the fitting too much. The result can be a cracked fitting or distorted threads and a leak. For putting together 1/2- to 1-inch pipe, a 12- to 14-inch pipe wrench is the right size; 1¼-to 1½-inch pipe requires an 18-inch wrench. Of course, taking apart an old system, if you are adding on, can require the biggest wrench you can find—old pipes are very stubborn.

To minimize strain on pipe and fittings as well as their supports, always use two wrenches. Place one on the pipe or fitting that's already installed to keep it from turning while you turn the other piece with the other wrench. A pipe wrench can be damaged if you use it the wrong way. You should always apply the pressure to turn a wrench in the direction of the open jaws. Wrenches must be set on the pipe in one way for assembling and the opposite way for taking apart, as shown in the drawing.

Repairing Iron Pipe

As described in the “Emergency Repair” section, a small leak in a pipe can be temporarily fixed with a piece of rubber and a clamp. You can more permanently repair a small leak with a special pipe clamp available at plumbing supply shops.

Small leaks around joints can sometimes be re paired by turning off the water and packing the leaky place with epoxy cement. Let the epoxy dry completely before turning the water back on. Tithe leak persists, you will have to unscrew the pipe and fitting, clean the threads with a wire brush, apply a thick coat of new pipe joint compound, and reassemble the joint.

If the leak in the pipe indicates that it's rusted out and must be replaced or if the joint leak is in a place where it's impossible to unscrew one or two fittings, you will have to cut the pipe. This is really not as bad as it may seem at first — thanks to unions.

First turn of all the water to this section of the system. With a hacksaw or pipe cutter, cut the leaking section of pipe or a section of pipe adjacent to the leaky fitting. The piece you cut will have to be at least 6 inches long in order to incorporate the union when it's replaced. Next unscrew the piece of cut pipe and , if you are re pairing a leaky joint, clean and apply new compound as described. Reassemble the joint.

Next measure the length of pipe you need to re place, subtract the distance that will be taken up by the union, and divide the remainder into two parts, not necessarily equal (see the drawing). Screw the two sections of pipe into the fittings on each end and then install the union as described.

Tools for Working with Threaded Pipe

Pipe vise. This vise is made especially to hold pipe and other round objects. It is quite expensive and , unlike a machinist’s vise or wood vise, can't be used for a lot of other household jobs. Unless you expect to do a lot of plumbing jobs over the years, you may want to rent a pipe vise instead of buying one.

Pipe cutter, reamer, and threader. These are all the tools needed, along with the pipe vise, to cut and thread pipe yourself. These, too, are quite expensive to buy just for one little job. They are available for rental in most areas.

Pipe Joint compound or Teflon tape. This joint com pound comes in cans, tubes, and sticks. The sticks are like big crayons that can be rubbed into the threads. Teflon tape comes in rolls like adhesive tape. The purpose of these items is to lubricate the pipe threads during the assembly of the pipe and fittings, to seal the threads so leaks are less likely, and to protect the threads from rust and other corrosion over the years.

Choose the material that's easiest for you to use. Joint compound has been around for a long time and has proven to be very effective. Teflon tape, the newest method of covering the threads, is quite easy to use and will protect the threads and prevent their rusting together for longer than the joint compound. We prefer the Teflon tape for most applications.

ill.30 Taking Apart Pipe: With one wrench, hold the piece next to the one you’re removing. Turn the piece you’re removing counterclockwise with another wrench. The wrench jaws should face in the direction you are applying pressure. With one wrench, hold the last piece you assembled. Screw on the next piece clockwise with the other wrench.

ill.31a Repairing Iron Pipe: If the leaky pipe is long enough to insert a nipple and a union, do it like this. If the leaky pipe is too short, replace it and insert the union in a nearby pipe that's long enough. New piece of pipe or old pipe, cut and rethreaded. Old pipe with small piece cut out, ends rethreaded, and a union installed

ill.31b Threaded Pipe Tools. Pipe joint compound


Wednesday, May 9, 2012 1:29 PST