The Drainage System

The drainage system is often referred to as DWV for Drain Waste and Vent. The purpose of the system is to carry away and dispose of waste water and dispel gasses created by decomposition within the system. DWV pipe and fittings materials include cast iron, galvanized iron, copper, PVC and ABS plastic. Your choice will depend on local codes, availability, budget and the project you are planning.

A number of adaptor fittings are available to tie the newer plastics into older systems for remodeling or additions. Consult your hardware salesman. He'll be glad to work with you or suggest a contractor who will do the more difficult work, or that work code requirements dictate be done by a licensed plumber. When you're working on a DWV system, keep three points in mind.

1. Always use sanitary fittings for drain lines. Sanitary fittings differ from vent and water fittings in that they are designed so waste flow is unrestricted.

2. To provide good drain flow, drainage pipes and fittings are installed to sloe down from 1/4" to 1/2" per foot.

3. Every fixture except toilets must be installed with a trap in the drainage system. Toilets are designed with a built-in trap. Traps are "U"-shaped devices that provide a water seat between the fixture and the drain to prevent sewer odors and vermin from entering the home.

Drain, Waste, and Vent Fittings

Typical drain waste and vent fittings are shown below. The appearance may differ slightly with the type of materials but the use and name is generally the same in all cases.

Plastic Pipe

Hot and cold plastic pipe is the most recent introduction in plumbing piping. It's called chlorinated polyvinyl chloride (CPVC for short). There are other types available. So before you decide on plastic, check local codes and your hardware salesman for the right type for hot and cold water, temperature and pressure limits. Plastic pipe is extremely easy to work with since all joints are cemented or welded together with a special cement or "solvent".

Allow for expansion and contraction and use hangers designed especially for plastic pipe installation. Use copper or galvanized for the first three feet of run from a hot water tank.

Galvanized Steel Pipe

Galvanized steel pipe is used for water and plumbing. Don't confuse it with black iron pipe (used for gas lines). It's inside diameter is always it's size. Buy standard 10-and 21-foot lengths or have pipe cut to order (better for simple jobs or replacing existing runs). Most hardware stores also carry many popular lengths precut and threaded. Galvanized steel pipe can be connected to copper or plastic with special adaptors. (see below)

Joining Dissimilar Material

Shown at right are "special" fittings and adaptors used for joining different type materials, supply lines and stop valves. Always use brass or red copper fittings when joining copper and galvanized iron pipe. Copper fittings connected directly to galvanized pipe will cause and electrolytic or corrosive reaction resulting in the erosion of the copper.

Copper Pipe

Copper pipe is sized according to it's inside diameter which varies slightly depending on the thickness of the wall. The outside dimension is always 1/8" more than the stated size. Copper pipe comes in rigid (hard temper) available by the foot in straight lengths and flexible (soft temper) which comes in 30- or 60- foot rolls. Soft temper or flexible is good for modernization and remodeling where lines go through existing partitions and walls with small openings. Hard temper or rigid is generally used in exposed areas since it does a better looking job and resists dents during the entire construction phase.

There are three types of copper pipe: Type "K"  Type "L" and Type "M"

1. Type "K", for underground use, is available in both rigid and flexible in diameters of 1/4", 3/8", 1/2", 3/4", and 1".

2. Type "L" is available in both rigid and flexible in 1/4" to 1" diameters. It is used for interior plumbing lines and is joined by solder, flare or compression fittings.

3. Type "M" comes in 3/8" to !" diameter in rigid only and must be used with soldered fittings. Because of it's thinner wall, type "M" is the least expensive of the three.

Flared fittings is used only with soft (flexible) copper tubing, with the tube end flared by a flaring tool. Flare nut must go on tube before flaring. Union for threaded pipe goes together as shown above. Compression fittings are used for copper tubing. Slip nut on tube followed by brass compression ring. Tighten nut on fitting to compress ring, and the job's done.

Soldering Copper Fittings

Soldering or "sweating" copper pipe and fittings is easy if you follow a few basic rules. You'll need a propane torch, a half-round metal file, emery cloth, soldering paste (called flux), and solder. 50/50 wire-type is best. A good soldered joint starts with a clean cut. Use a fine tooth-hacksaw blade or tube cutter. A tube cutter makes a cleaner cut. If you use a saw, cut the tubing in a mitre box as shown in the illustration. If you use a tubing cutter, tighten it slowly to avoid crimping the tube.

Next, check the fit between tube an joint. A loose fit will not  provide a good bond. Keep it clean. You cannot solder a dirty connection. After cutting, remove all burrs (inside and outside with the file). Clean the tube and the fitting with emery cloth. It won't take much.

When the surface is bright and shining, brush a small amount of flux on both the tube and fitting. Flux keeps the surface bright and provides for a smooth flow of solder over the two surfaces being joined. Keep your flux clean, and use a small brush reserved for flux only. Join the tube and fittings. Check the alignment, and you're ready to solder. Don't melt the solder with the torch. The solder is melted from the right amount of heat in the tube end and fitting. Start heating the tube end first. After a short period start heating the fitting and tube, gradually directing the flame alternately between the tube and fitting.

When the solder starts to melt, move the flame all around the entire joint. After the joint is full of solder (it happens quickly), remove the flame. DON'T OVERHEAT. That's it. The joint will cool quickly. Before it does, wipe excess solder off with a clean cloth. If you did a good job, you'll have a bond that's stronger than the tube and fitting.

Soldering Valves

Be sure that the valve is opened all the way before soldering. If not, heat might damage the seat. Don't use too much solder. Excess solder could clog the valve seat. Soldering  procedures are the same as for fittings.

Repairs and Additions

Close the main water shut off valve. Open faucets below the area you are working to drain water from the lines. (If water or moisture is present, you won't get the area hot enough to melt the solder). To unsolder a joint, heat it to melt the solder, then pull the pipe out of the fitting. Protect other connections in the connection with a wet rag.

Solvent Welding Plastic Pipe

PVC and CPVC plastic pipe and fittings are actually welded together using a special primer followed by a solvent. ABS plastic welding needs only ABS solvent to weld the joint. If in doubt, check where you purchased the pipe and fittings. There is no "universal solvent". Plastic piping can be cut with a hacksaw and mitre box or a tubing cutter with a sharp blade.

A ten foot length of plastic pipe will expand 1/2" when heated from room temperature to 180 degrees. Allow for this expansion and contraction when running lines and use hangers designed for plastic pipe. If you are running from a hot water tank, use copper tubing or galvanized iron pipe for the first three feet. The inside walls of plastic fittings are tapered so the  pipe makes contact with the sides of the fitting before the pipe is firmly sealed. This is called a interference fit. After you have applied the cleaner and/or solvent, the material softens and compresses allowing the pipe to be forced all the way into the fitting.

Start with a square, clean cut. Remove all burrs with a sharp  pocket knife or deburring tool. Check for interference fit. The pipe should go in the fitting about halfway. Apply cleaner (PVC and CPVC only) to the inside of the fitting then to the outside of the pipe to the sealed depth. Don't use too much. There shouldn't be  puddles of liquid in the fitting. Wait 5 to 15 seconds and apply solvent while the surfaces are still wet from the  primer. Again, don't use too much but cover all the surfaces previously coated with primer.

Join pipe and fitting before the solvent dries. Force the pipe into the fitting until the pipe bottoms out, turning as you push it in. Then hold the pipe and fitting together for about 10 seconds (or longer in cold weather).

Check the bead of solvent that has been pushed out. It should go all the way around the joint. If it doesn't, you haven't used enough cement and the joint could leak. Wipe off excess cement leaving a neat fillet around the fitting. It looks neater and helps the joint cure faster.

Allow joint to "cure" before testing. Allow at least one hour cure time when temperatures are at 60 to 100 degrees F, at least two hours at 40 to 60 degrees F, at least eight hours at temperatures below 40 degrees. Increase times by 50% where relative humidity is above 60%.

Galvanized Steel Fittings

Before making a steel pipe joint, remove all dirt and chips from inside the pipe and around the threads. Apply pipe joint compound to the pipe threads only. Never to inside threads. Use just enough to fill the threads evenly with no bare spots. Start the threads by hand to make sure you have not cross threaded them.