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    The Advantages and Disadvantages of Different Material Pipes

 

Over the years, the art and science of plumbing has changed dramatically. From the first Terra Cotta pipes in about 1700 B.C. to the newest PEX pipe technology today, no building is complete without plumbing. If it weren't for plumbing and plumbing professionals, the urban sprawl that we have experienced today would not have been possible. And if it weren't for pipes, plumbing would not be possible either. In this article I will discuss and compare the advantages and disadvantages of many of the pipe technologies that have existed or currently exist on the market for residential use.


Cast Iron Pipe

In the 1960's cast iron pipes were the most popular form of plumbing in residential construction. This pipe was cheap and relatively easy to install for its time. It was also noted for its strength and ability to withstand high pressures. At the time, this made it ideal for home installation. Unfortunately for cast iron, it had one major flaw. This pipe was prone to failure due to rusting. Most cast iron plumbing systems had at least one leak within 20 years of installation, but many homes had more than their fair share of plumbing problems. Cast iron pipes were also known to leave a metallic taste the water. This was due to the iron leaching into the water from the rusting of the pipe. Today, cast iron pipe is no longer used for residential plumbing because of its faults.

Copper Pipe

Copper is probably the most commonly used plumbing materials in the United States today. This plumbing material offers long term durability and stability yet is soft enough to resist shattering upon impact. Its so durable in fact that copper pipes can even be used outdoors in both above and underground setting. Another advantage to copper plumbing is its natural ability to resist the growth of bacteria. This is important because it helps to ensure that your water supply is clean and safe to use. And finally, copper has a very high melting point and is able to resist deformation. This means that during a house fire, the plumbing may remain intact and could possibly be reused.

Despite all the great things that copper has to offer, there are a few disadvantages. The first notable disadvantage is the fact the copper is expensive to purchase and install. Installation of this plumbing requires soldering equipment and the skills of a trained plumber. Copper pipes can also be subjected to major corrosion if the water it contains becomes too acidic. In addition to this, copper pipes can leave water with a slightly metallic taste.


PVC Pipe

Next to copper, PVC pipe is also one of the most common materials used for residential plumbing applications. PVC is great because it is an inert and stable material that resists corrosion. It is also a very cheap material that is quick and easy to install. A minimal amount of skills and tools are required to properly install PVC pipes in a home.

The main disadvantages to PVC pipe is that it is very brittle that can break or crack if miss-handled. This is especially true for properties located in cold climates. In addition to this, it can only be used indoors and is not intended for hot water distribution (it has a maximum service temperature of 140 degrees Fahrenheit). Because of this, care must be taken when installed near hot items such as furnaces or ovens.


CPVC Pipe

CPVC stands for Chlorinated Polyvinyl Chloride. This yellowish plastic polymer was invented to handle the higher temperatures that regular PVC could not. It also is slightly stronger than standard PVC. CPVC has a few advantages over copper as well. It is generally a stable compound and will not corrode as easily as copper pipes can. CPVC also requires about 25% less time to install than copper does (though it does require more bracing). However, it is not as easy to install as other plumbing materials such as PEX.

The disadvantages of CPVC include that it is brittle and it can't withstand very high temperatures like copper can. Another disadvantage to CPVC is it's high thermal expansion coefficient. Because of this, CPVC may not be the best choice for climates that experience wide variations in temperature. Additionally, CPVC typically costs about twice as much as standard PVC does.


PEX Pipe

PEX is shorthand for "Cross-Linked polyethylene." This material is relatively new to the field of plumbing (only appearing in the USA about 20 years ago) and offers some clear advantages over other available materials. The first, and most notable, characteristic about this material is that it is flexible. The flexibility of the pipe allows installers to avoid many obstacles while also using less fittings. The speed of installation is also increased by the fact that the pipe fittings are generally of the compression type. And finally, PEX is very good at resisting the effects of freeze and thaw because of its flexibility.

However, there are some disadvantages to this material. Installation generally requires the use of extensive bracing and supports. If not done properly, the pipes can move within the walls when the water is turned on and off (water hammer). PEX cannot be used outdoors unless it has a UV blocking coating. PEX is also a softer material that rodents seem to enjoy chewing on. This can lead to a sudden and catastrophic loss of water pressure (and potential water damage) within a home.

Summary

The overall consensus is this: Plastic pipes are the cheapest to purchase and install, however they generally cannot be used outdoors and have relatively low service temperatures. Copper is the way to go if you need to deliver hot water or want something that this durable and long lasting. Today, many houses are being constructed using a combination of PEX and copper plumbing. This combines the ease of installation of PEX with the durability and strength of copper. This affords new homeowners the best combination of advantages that the residential plumbing industry has to offer.

Below is a table which summarizes the key characteristics and information for the various types of plumbing materials for comparison purposes.

Comparison of Properties for Common Pipe Materials

 

Cast Iron

Copper (Type M)

CPVC (Schedule 40)

PVC (Schedule 40)

PEX (Class A)

Cost

N/A

$3.90/ft

$0.83/ft

$0.20/ft

$0.46/ft

Pressure Rating @ 73°F

200 psi

225 psi

400 psi

100 psi

150 psi

Pressure Rating @ 180°F

200 psi

120 psi

100 psi

N/A

100 psi

Max Service Temp

200 °F

200 °F

200 °F

140°F

200 °F

Softening Point (Vicat Test)

N/A

N/A

295 °F

250 °F

255 °F

Melting Point

2,300 °F

1,981 °F

428 °F

360 °F

270 °F

Thermal Expansion

0.000006 in/in/°F

0.000009 in/in/°F

0.000037 in/in/°F

0.000028 in/in/°F

0.000083 in/in/°F

Tensile Strength @ 180°F

25,000 lbs

34,800 lbs

8,700 lbs

6,500 lbs

1,806 lbs

Weight

12.2 lbs/ft

0.33 lbs/ft

0.23 lbs/ft

0.21 lbs/ft

0.1 lbs/ft

Specific Gravity

7.89

8.96

1.54

1.4

0.94

Corrosion Resitance

Low

Medium

High

High

High

Life Expectancy

20-75 years

50-75 years

75-100 years

75-100 years

75-100 years

Flexibility

None

Slight

Slight

Slight

High

Thermal Conductivity

3.8 Btu in /h ft² °F

19.2 Btu in /h ft² °F

1 Btu in /h ft² °F

1.1 Btu in /h ft² °F

3.2 Btu in /h ft² °F

Specific Heat

0.11 Btu/lb °F

0.09 Btu/lb °F

0.2 Btu/lb °F

0.25 Btu/lb °F

0.55 Btu/lb °F


The data for this table was compiled from more than 100 resources including textbooks, websites, and other technical guides.

Properties given are for 3/4" or equivalent pipe except for Cast Iron which has a diameter of 3 inches.

Joining Method and material will govern the pressure rating for copper. In this table, a 50-50 tin/lead solder is used because it is the weakest of all the common copper joining methods.

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