Metal Pipes Used in Plumbing
A Brief Overview of the Various Types of Plumbing Applications
To some, it may seem that the variety of different metalic pipes used in plumbing is somewhat unnecessary. They all do serve important and distinct puprposes, though.
Head down to the basement of a modern home and (provided there is no sheetrock or insulation covering the ceiling), you might be able to witness a jumbled maze of various pipes of different sizes, shapes and materials, spreading out through the floor joists like a complex, water carrying spiderweb. Anyone with little to no experience in plumbing will surely be both mystified and repulsed by this unnecessarily complex organism.
After all, what could be the purpose of all those different pipes? Why not just use one type for every application? The trick is to know that each pipe should be serving a distinct function. Knowledge of these functions can help to take some of the mystery out of a home plumbing system.
There are just a few standard types of metal pipe:
Galvanized
Galvanized pipes are heavy metal pipes with a dull grayish-silver exterior. They have been used for both hot and cold plumbing applications in homes for many decades, but their use is beginning to wane as of late, for in certain applications other, simpler pipes have taken their place.
Commonly, galvanized pipes are used to carry water outside the home, especially when buried underground (the other alternative to this is to use a heavy plastic polypipe). Because of thier galvanized coating they are somewhat resistent (though not impervious) to rust. They do tend to rust fairly easily along the threaded ends, however, where the coating has been cut away.
Generally, galvanized pipes within the home today are being replaced either by copper pipe (though this option is growing very expensive as of late) or a more moder plastic PEX system, which is rather reliable and not prone to the corrosion prevalent in galvanized systems.
Galvanized pipe regularly comes in 1/2", 3/4", 1", 1 1/4", 1 1/2" and 2", though other sizes (such as 1/4" and 3/8") may also be available (though more limited).
CopperCopper today is probably the most common type of pipe used for water carrying lines behind the walls of homes. Because of its high resistence to corrosion and tolerence of heat, copper is ideal in both hot and cold applications. In addition, because it is usually connected using soldered fittings, their fittings become permanent additions, and don't often come loose.
The downsides to copper are almost as self-evident as its benefits. It has become very expensive in recent years, making it a valuable commodity and a high-theft item at hardware stores, driving the price even higher. Indeed, one does not envy the person who decides to plumb an entire home with brand new copper these days. Such a project would be extremely expensive (a common alternative today is to use either a PEX system or to incorporate CPVC to carry hot water).
In addition, many homeowners are not familiar with soldering techniques, so building a copper system can be difficult at first, while other, more user-friendly fitting options (such as "Sharkbite" fittings) will cause costs to skyrocket even further.
Copper comes in a variety of styles and sizes - rigid type L copper (medium wall) is what is most commonly used for home plumbing, while other applications might call for type M (thin wall) and type K (thick-wall). In addition, there is the option of "soft copper" which is a flexible tubing that is used to go around corners and as supply lines for sinks and toilets (1/4" soft copper is probably the most commonly used, as it is utilized in most ice maker and refrigerator supply applications).
Stainless SteelSomewhat rarer than either galvanized or copper pipe is stainless steel pipe. It is expensive and somewhat difficult to come by (which explains why it is not commonly used), but can be very useful for highly corrosive envioronments, such as in marine use or in homes near the ocean, where winds might blow the corrosive salt water toward the house.
Black Iron
Black iron is not exactly plumbing pipe, but it included here as this is a common mistake. Black pipe is similar in size and price to galvanized pipe, but is used for carrying gas (never water). Because it does not have any protective coating, black pipe rusts very easily, and if used in water applications can be potentially toxic.Because it holds gas instead of water, black pipe should not be attached using standard white teflon tape. Instead, there is specially-formulated yellow tape and/or thread compound which is used in these applications.And those are just a few of the more common types of metal tubing you might see if you happened to look under the floor (or in the walls) of the average home today. To learn about the plastic pipes and tubing, you may click here.
