In this video, This Old House plumbing and heating expert Richard Trethewey takes a look at the wide variety of water-supply pipes.
Steps:
1. Galvanized steel pipe is no longer used for supplying water, but it’s still found in some older homes.
2. Home centers and plumbing-supply stores have fittings for connecting copper and plastic water-supply pipe to existing galvanized pipe.
Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, explains the history: “During the war effort, they moved from threaded brass to save the precious metals for the armaments. And they went to this. As its name suggests, it’s a steel piping with a galvanized coating both on the outside and on the inside to keep it from rusting. And over time, that coating would wear away, and it would start to rust, and it would rust from the inside.”
Pro Tip: When connecting new copper pipe to existing galvanized steel, beware of electrolysis — a corrosion problem caused by dissimilar metals touching. Richard Trethewey recommends using a dielectric union, which features a rubber gasket that prevents the two metals from making direct contact: “If we have the presence of even the slightest amount of electricity, we’ll have oxidation where the two metals meet.” The dielectric union breaks that electrical current and prevents the joint from rotting out.
3. Copper tubing is the most popular water-supply pipe; it’s available in 10-foot and 20-foot lengths.
4. Type L copper tubing has thick walls and Type M has thin walls. Check with the local building code to determine which type to use.
5. Copper pipe and fittings are sweated together with solder.
6. Solder-less copper compression fittings are also available. Tighten the fittings with two wrenches.
7. Push-on copper fittings form watertight connections without using any tools. Use these fittings for repairs in tight spaces.
Pro Tip: Push-on copper fittings use stainless steel teeth and an O-ring inside the fitting to create a watertight seal. As Richard Trethewey, This Old House plumbing and heating expert, explains: “You’re not gonna do a whole house with it. But if you’re in a tight space trying to make a connection, it could be a real lifesaver for you.”
You can tell the difference between Type L and Type M copper by the color printed on the outside of the pipe. Type L is marked with blue lettering, while Type M is marked in red. Both types share the same outside diameter, but Type M has a thinner side wall, which means a slightly larger inside dimension. In many jurisdictions, Type M is not allowed for potable water because of concerns about water velocity inside the thinner walls.
8. You can use CPVC plastic piping to supply water, but not PVC, which is only rated for drainage.
9. Join together CPVC pipe and fittings with brush-on primer and cement.
Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, explains: “The ‘C’ stands for chlorinated polyvinyl chloride, and that’s good for use with water.” He notes that CPVC comes in standard 1/2-inch and 3/4-inch sizes, and the connections look similar to copper fittings with T’s and elbows—but instead of soldering, “we would actually use a cleaner and a special cement that will allow us to fuse those pipes together.”
10. PEX cross-link polyethylene water-supply tubing comes in coils or straight sticks.
11. Blue PEX is for supplying cold water; red PEX is for hot water.
12. PEX tubing and fittings can be connected with crimped fittings, which are joined tightly together with a crimping tool.
13. PEX can also be connected with barbed brass fittings. Use an expander tool to widen the tubing end, then insert the barbed fitting.
14. Use the expander to force the fitting fully into the tubing end.
