Types of Piping Systems
Most homes built since the mid-1970s have plastic pipes and fittings, which are rated by the American Society for Testing and Materials (ASTM). Plastic pipes can be used for pressurized applications, such as potable (drinking) water systems, hot- and cold-water distribution, and irrigation systems. They can also be used for nonpressurized applications (gravity flow), such as sewage, drainage and storm drain systems. Homes built prior to 1960 used galvanized steel or cast-iron pipes for drain/waste/vent (DWV) systems. DWV systems remove wastewater and prevent the flow of sewer gases into homes. The most common types of plumbing pipes used in homes today are copper and polyvinyl chloride (PVC), both of which are strong, long lasting and easy to install. Other choices include chlorinated polyvinyl chloride (CPVC) and PEX pipe.
Copper Pipes vs. CPVC Pipes
Whether copper or CPVC piping should be used to deliver a home’s drinking water will vary from home to home. Here are some pointers to help you determine the best choice:
- Water Types: In many areas, particularly those without municipal water sources, the acidity of the home’s water may be a factor in choosing the right types of plumbing pipes. Highly acidic water can break down copper pipes over time and cause green staining in fixtures. Although passive water filters can deal with acidity, they must be recharged every year or so. Because of this, owners sometimes opt for acid-indifferent CPVC piping.
- Installation Time: CPVC must not be pressured for 24 hours after installation to allow the pipe adhesive to set properly. Copper can be used within minutes of installation.
PEX Pipes
PEX pipes differ from traditional rigid pipes in one obvious way: They’re flexible. This makes it easier to snake them to different areas of a home. Using PEX piping may require running more pipe, but it also involves fewer fittings. PEX crimp tools offer a simple way to make these flexible fittings more secure and watertight.
Here are a few other advantages of PEX:
- It’s quieter than rigid piping.
- It has a smooth interior that resists scale buildup and corrosion, which can affect pipe flow over time.
- It’s freeze-break resistant, although not freeze-proof. PEX tools, such as specialty expansion kits, will enhance this benefit by absorbing dimensional changes caused by thermal expansions/contractions.
- PEX systems have appealing installation costs compared to rigid materials.
- PEX piping is often used in green buildings, installed either as a remote manifold or plumbing system.
PEX pipe and crimp fittings, with all their benefits, do have a drawback: Because UV exposure causes a reaction with polyethylene, it isn’t suitable for outdoor use. The maximum level of UV exposure is typically no more than 60 days, but this varies by manufacturer. Using PEX for underground water supplies isn’t ideal, even if UV exposure is decreased.
Have PEX specialty tools on hand to ensure you can make full use of PEX piping advantages.
Materials for DWV Pipes
- Cast-iron pipe and fittings (black)
- PVC Schedule 40 (SCH 40) DWV pipe and fittings (white; used in irrigation, underground sprinkler systems, swimming pools, outdoor applications and cold-water supply lines)
- Acrylonitrile butadiene styrene (ABS) DWV pipe and fittings (black, common in the western US)
Materials for Pressurized Systems
- PVC Schedule 40 (SCH 40) pipe and fittings (white; straight, angular turns; designed for potable water under pressure into buildings)
- Copper tube size (CTS) chlorinated polyvinyl chloride (CPVC) pipe and fittings (cream or tan, used for hot or cold water, sized similarly to copper pipe sizes)
- PVC Schedule 80 (SCH 80) pipe and fittings (dark gray, withstand higher pressure, designed for the distribution of pressurized liquids)
PVC SCH 40 DWV Pipe and PVC DWV Fittings for Nonpressurized Applications
PVC DWV fittings can be installed with foam core pipe or dual-marked solid wall pipe. ASTM F 891-rated foam core pipe is lighter and less expensive. Solid wall PVC pipe is often rated for both pressurized (ASTM D 1785) and nonpressurized (ASTM D 2665) applications (often referred to as dual marked). When solid wall or foam core pipe is used with PVC DWV fittings, the resulting system isn’t pressure rated.
Description
- White, rigid pipe and fittings
- Joined with solvent cement, conforming to applicable ASTM standards
- Have a gradual, sanitary turn
Application
- Draining household sanitary waste (kitchen, bathroom) and groundwater
-
Not for pressurized applications or compressed air/gases
Joining Method
- Solvent cements must meet ASTM D 2564 standard
- Primer is required
- May be joined with a slip-joint compression fitting (a trap adapter)
- Threading PVC 40 pipe isn’t recommended
- Male iron pipe (MIP) and female iron pipe (FIP) size adapters are available
PVC SCH 40 Pipe and Fittings for Pressurized Applications
Description
- White, rigid pipe and fittings
- Joined with solvent cement, conforming to ASTM D 2564 standard
- Straight, angular turns
- Not for gradual sanitary turns for pressure systems
Application
- Distributing potable water under pressure into a building (not to be used inside)
- Irrigation and sprinkler systems
- Draining condensate waste from heating and air conditioning systems
- Not for compressed air or gases
Joining Method
- Solvent cements must meet ASTM D 2564 standard
- Primer required
- May be flanged with SCH 80 flanges
- Threading PVC 40 pipe isn’t recommended
- MIP and FIP adapters are available
PVC SCH 80 Pipe and Fittings for Pressurized Applications
Description
- Dark gray, rigid pipe and fittings
- Joined with solvent cement conforming to ASTM D 2564 standard
- Straight, angular turns must be used
Application
- Distributing pressurized liquids
- Can be used in industrial applications
- Not for use with compressed air or gases
Joining Method
- Solvent cements must meet ASTM D 2564
- Primer should be iron pipe size (IPS) P-70 or Oatey Industrial Grade
- May be flanged with SCH 80 flanges
- Threading PVC 80 pipe can be done
- MIP and FIP adapters are available
ABS Foam Core SCH 40 DWV Pipe and ABS DWV Fittings for Nonpressurized Applications
Description
- Black, rigid pipe and fittings
- Joined with solvent cement conforming to ASTM D 2235 standard
- Fittings have a gradual sanitary turn
Application
- Draining household sanitary waste (kitchen, bathroom) and groundwater
- Not for use with pressurized applications or compressed air/gases
Joining Method
- Solvent cements must meet ASTM D 2235 standard
- Primer isn’t recommended
- May be joined with a slip-joint compression fitting (a trap adapter)
- Threading ABS-40 foam core pipe isn’t recommended
- MIP and FIP adapters are available
CTS CPVC Pipe and Fittings for Pressurized Hot- and Cold-Water Applications
Description
- Cream or tan, rigid pipe (with a gold stripe) and fittings
- Joined with solvent cement conforming to ASTM F 493 standard
Applications
- Distributing hot and cold potable water under pressure
-
Not for use with compressed air or gases
Joining Method
- Solvent cements must meet ASTM F 493 standard
- Yellow FlowGuard Gold cements may be used without primer, where approved by code
- Compression fittings with a brass ferrule may be used
- Threading the pipe isn’t recommended; use CTS CPVC male adapters in cold-water applications only; use CTS CPVC brass-threaded transition fittings for hot-water applications
Don’t use compression fittings with brass ferrules to connect to CTS CPVC pipe or fittings where water temperatures exceed 140 degrees Fahrenheit.
Choosing Correct Pipe Sizes
Plumbing beginners often purchase pipes that are too small. To avoid this mistake, it’s helpful to understand the difference between actual measurements and nominal measurements. The word “nominal” roughly means “in name only.” For example, if you need a pipe that has an actual diameter of 1/2 inch, the one you purchase may not be labeled as a 1/2-inch pipe.
Next, identify what kind of plumbing pipe you’re using. Copper, plastic/steel and cast-iron pipes all require different sizing conversions. Knowing your piping material will help you convert your pipe’s nominal measurement to its actual measurement.
Nominal copper pipe sizes are 1/8 inch less than the outer-diameter measurement. Cast-iron pipes’ nominal sizes are around 1/3 inch less than their outer-diameter measurement. Plastic and steel pipes’ nominal sizes use the same conversion and are around 1/3 inch less than their outer-diameter measurement.