When installing or replacing the plumbing under a kitchen sink, it is important to use the right type of pipe to ensure durability, leak resistance, and compliance with local building codes. The most common types of pipes used for kitchen sink drain lines and water supply lines are galvanized steel, copper, PVC, CPVC, and PEX.
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Galvanized Steel Pipes
Galvanized steel pipes were commonly installed under kitchen sinks for much of the 20th century. This type of pipe is made from steel that has been coated with zinc to prevent rusting and corrosion. Galvanized pipes are durable, rigid, and were once considered the industry standard.
However, galvanized steel pipes have fallen out of favor for use under kitchen sinks and are no longer recommended. Over time, the zinc coating erodes and the pipes start to corrode from the inside out. Galvanized pipes are prone to buildup and clogging. They can also develop pinhole leaks and lead to low water pressure. Replacement is recommended if galvanized pipes are still present under a kitchen sink.
Advantages of Galvanized Pipes
- Durable and rigid
- Inexpensive
Disadvantages of Galvanized Pipes
- Prone to corrosion and buildup over time
- Can develop leaks
- Replacement recommended
Copper Pipes
Copper is now considered one of the best options for kitchen sink plumbing. This pipe is made by bending copper tubing into the desired shape. Copper possesses many advantages that make it a top choice for under sink water lines.
Copper is highly resistant to corrosion. The copper itself has anti-microbial properties. Copper pipes are also very durable and can last 50 years or more with proper installation. The pipes are rigid but can still be snaked around obstacles under the sink.
In addition, copper is ideal for use with potable drinking water. It doesn’t impart any tastes, odors, or toxins into the water. Copper allows for good water pressure while resisting scale buildup.
The main drawback of copper pipes is that they tend to be one of the more expensive options. Installation also requires soldering tools and joints to connect the pipes. Nonetheless, the long lifespan and reliability of copper pipes make them a sound investment.
Advantages of Copper Pipes
- Corrosion resistant
- Antimicrobial
- Does not affect taste or odor of water
- Can last 50 years or longer
Disadvantages of Copper Pipes
- Relatively expensive
- Requires soldering for connections
PVC Pipes
PVC (polyvinyl chloride) is a plastic piping commonly used for sink drain lines. It is the white rigid pipe usually found under kitchen sinks or bathroom vanities.
PVC is suitable for drain lines as it is durable, inexpensive, and easy to install. PVC pipes are assembled with cements and fittings rather than soldering. The joints seal tightly and are corrosion proof.
Since PVC is lightweight, pipes are easy to maneuver under sinks during DIY installations. PVC also resists weathering and chemical corrosion. This type of plastic piping has good flow capacities for efficient drainage.
On the downside, PVC is not recommended for water supply lines, as chemicals can leach out over time. It also lacks the appearance and longevity of copper piping. Still, PVC remains a practical and affordable solution for kitchen sink drains.
Advantages of PVC Pipes
- Durable and corrosion proof
- Lightweight for easy installation
- Low cost
Disadvantages of PVC Pipes
- Not suitable for water supply lines
- Can leach chemicals
CPVC Pipes
CPVC (chlorinated polyvinyl chloride) pipes are another plastic piping option for under the kitchen sink. CPVC is PVC that has been fortified with extra chlorine molecules to make it more rigid and durable.
CPVC pipes can withstand temperatures up to 200° F. This makes CPVC suitable to use for hot and cold water supply lines. It is typically white or off-white in color.
Like PVC, CPVC assembles with solvent cements and fittings. It is easy to install without soldering. CPVC is also corrosion proof. If codes permit, it can be used for sink drains as well.
While CPVC lasts longer than PVC, it is still seen as an intermediate step before more permanent copper piping. CPVC is also prone to becoming brittle over time. The plasticizers in CPVC may also leach out and contaminate water. Overall, it offers a temporary water line solution.
Advantages of CPVC Pipes
- Withstands high temperatures
- Can be used for hot and cold water lines
- Easy to install
Disadvantages of CPVC Pipes
- Can become brittle and crack over time
- Chemicals can leach into water
- Not as durable as copper
PEX Pipes
PEX (cross-linked polyethylene) piping has emerged as another alternative to copper for under sink water lines. PEX tubing is flexible plastic tubing that comes off spools for installation.
PEX doesn’t require any soldering or gluing to install. The tubing is run from point to point and fastened in place with PEX fittings that form tight compression joints. PEX is affordable, easy to install, and suitable for hot and cold sink water lines.
Additionally, PEX is highly heat and corrosion resistant. It can withstand freezing temperatures without bursting. With no joints that can leak, PEX reduces the risk of water damage.
On the downside, PEX has only been in use since the 1960s so there are some uncertainties about its long term durability. The tubing needs to be shielded from UV light and should not be painted. Overall, PEX offers a flexible alternative to rigid copper piping.
Advantages of PEX Pipes
- Flexible and easy to install
- Affordable
- Withstands temperature extremes
- Resists corrosion
Disadvantages of PEX Pipes
- Long term durability unknown
- Cannot be exposed to UV light
Choosing the Best Pipe for Under a Kitchen Sink
When deciding what type of pipe to use for under a kitchen sink, here are some guidelines to consider:
- For drain lines, use PVC or ABS plastic piping if permitted by codes
- For water supply lines, use copper piping for durability and reliability
- CPVC or PEX can provide cheaper alternatives to copper but may need eventual replacement
- Avoid galvanized steel pipes which can corrode and result in leaks
- Use pipes approved for potable water use only
- Consider noise – plastic pipes tend to muffle noise better than rigid copper
- Match water pressure and temperature ratings for hot and cold water lines
- Review local building codes for approved materials
The right kitchen sink plumbing should last for decades without leaks, corrosion, or flow problems. Investing in quality, code-approved pipes such as copper will provide peace of mind and prevent expensive repairs down the road.
Conclusion
The most common types of pipes for kitchen sink plumbing are galvanized steel, copper, PVC, CPVC, and PEX. Of these, copper remains the gold standard material for water supply lines due to its durability, longevity, and reliability. PVC and ABS plastic pipes are cost-effective choices for the drain line. Homeowners should avoid outdated galvanized steel and may opt for CPVC or PEX as cheaper alternatives to copper that may eventually need replacement. When installed properly using approved materials, new kitchen sink plumbing should last 30 years or more without issues.