The pipes used to transport potable drinking water in a home plumbing system use different materials than those used for the pipes carrying drain water. Your home may have a plumbing system that uses all one type of material for the water supply pipes, but don't be surprised to find several types of pipes, especially in older homes that have had many plumbing repairs or updates.
Here are some common materials used for water supply pipes.
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Galvanized pipe is steel pipe that has been treated with a zinc coating. This galvanized coating keeps the water from corroding the pipe. It was once the most common type of pipe for water supply lines, but because labor and time that goes into cutting, threading, and installing galvanized pipe, it no longer used much, except for limited use in repairs. However, galvanized pipe for water distribution is still seen in larger commercial applications.
If you have a pre-1960s house, you could still have galvanized water lines in your house. Galvanized piping has a functional life of about 40 years, according to home inspection agencies. If your galvanized steel plumbing system is approaching that age, an upgrade is probably advisable. If the pipes are still in good condition, hardware stores carry a variety of fittings and can cut and thread galvanized pipes to match your needs.
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Copper pipe is mostly used for hot and cold water distribution, as well as being regularly used in HVAC systems for refrigerant lines. Although once used in gas piping, this is no longer allowed in some jurisdictions. Copper piping works in both underground and above-ground applications, but copper can be affected by some soils and it should have a protective sleeve if used underground.
For many years, copper was the gold standard for water supply pipes, as galvanized steel fell from favor. Copper plumbing pipes can last for up to 50 years, but as it ages, copper thins out, eventually leading to pinhole leaks. More recently, various forms of plastic have replaced copper as the favorite, though copper pipes and fittings are still widely available. Due to the price of copper and the longer labor needed to install, many builders have switched to alternative water distribution piping, especially PEX. Depending on the city you live in or commercial versus residential applications, copper is still used widely over CVPC and PEX tubing.
Copper comes in different thicknesses which are labeled M, L, and K. M is the thinnest grade of copper. Copper can be connected in different ways, including compression fittings, push-fit fittings, or sweat-soldering. K copper is used in underground applications and high pressure situations. M copper tube is used in heating applications and isn't allowed for water lines in some jurisdictions because it cannot withstand high pressure water.
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PVC is an acronym that stands for polyvinyl chloride. Of the different types of plastic pipe used for water supply, PVC pipe has a wide variety of plumbing uses but is mostly used for drainage PVC is rarely used in potable water applications, and in many jurisdictions it is not considered safe for drinking. PVC is also very common in pool and spa systems. PVC pipe is often white but it can also come in other colors. You can often tell what it is used for by the colors and marks on the pipe. For example, purple pipe with black lettering is sometimes used for reclaimed water. PVC also comes in a variety of thicknesses, called schedules. Schedules 40 is common for pipes used in water distribution.
PVC connections are made by using a primer that softens the PVC and then applying PVC glue that melts the joints and pipe together. CPVC pipe should always be clearly labeled if used for potable (drinkable) water. In commercial applications, all piping systems are labeled.
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The acronym CPVC stands for chlorinated polyvinyl chloride. It is often (but not always) cream-colored or off-white plastic. This type of pipe can stand temperatures up to about 180 degrees Fahrenheit or so (this depends on the schedule), so it can be used for both hot and cold water lines.
According to the International Association of Certified Home Inspectors (InterNACHI), CPVC and PVC pipes generally last for 50 to 80 years under perfect conditions, though early failure is also reported in some circumstances.
As with PVC, you should use primer and glue when making a CPVC joint. Also, make sure the glue specifies that is can be used on CPVC.Continue to 5 of 5 below.
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PEX stands for cross-linked polyethylene. It is sometimes known as XLPEl. With good resistance to both hot and cold temperatures, PEX is commonly used for both hot and cold water lines in homes, and for hydronic heating systems (such as radiant under-floor systems).
PEX is considered more durable than copper, with a likely lifespan of more than 50 years. For professional plumbers, PEX tubing has now largely replaced copper and other plastics used for water supply pipes. They prefer PEX because of its low cost, and because it comes in long rolls of tubing that are easy to transport. Because the flexible tubing can be bent around corners, fewer elbows and other fittings are required, speeding up installation.
PEX can be joined in many different ways, including push-fit fittings and crimp rings secured with specialty PEX tools.
Healthy Housing Reference Manual: Chapter 9: Plumbing. U.S. Centers for Disease Control and Prevention.
InterNACHI's Standard Estimated Life Expectancy Chart for Homes. International Association of Certified Home Inspectors.
Designing PEX Plumbing Systems to Optimize Performance and Efficiency. American Society of Plumbing Engineers.