How To Replace a PVC Sink Trap

A leaky sink trap can be a frustrating plumbing issue for homeowners. Fortunately, replacing a polyvinyl chloride (PVC) sink trap is a manageable DIY project that can save you money on professional repairs. This guide will walk you through replacing a PVC sink trap, helping your plumbing system function properly and remain leak-free. In the video above, This Old House plumbing and heating expert Richard Trethewey demonstrates how to replace a leaky, glued-together kitchen sink trap.

Steps To Replace a PVC Sink Trap

Replacing a PVC sink trap involves several key steps. Here’s a detailed breakdown:

1. Prepare the Work Area

Before you begin the trap replacement process, clear and prepare the area under your sink as follows:

1. Place a bucket or pan beneath the trap to catch any water.
2. Wear safety glasses and work gloves to protect yourself.
3. Have paper towels on hand to clean up any spills.

2. Remove the Old Trap

Next, you’ll need to remove the old PVC sink trap by following these steps:

1. Use pliers to remove the drain plug from the bottom of the sink trap. This will allow any remaining water to drain into your bucket.
2. Use a reciprocating saw to remove the existing PVC sink trap. Make your cuts as close to the fittings as possible to maximize the pipe available for the new installation.
3. Loosen the compression fitting that connects the trap to the sink drain and remove the entire PVC assembly.

3. Clean the Existing Pipe

After you remove the old trap, a small section of PVC pipe may still be attached to the wall drain. Follow these steps to remove this pipe section:

1. Use a special PVC cutterhead attachment for your drill.
2. Insert the cutterhead into the remaining pipe section.
3. Carefully cut away the old pipe without damaging the fitting in the wall.

4. Prepare the New Assembly

Before you install your new PVC sink trap, you’ll need to prepare the new assembly as follows:

1. Dry-assemble (without glue) the new sink trap using 1 1/2-inch PVC pipe and fittings.
2. Test-fit the assembly under the sink to create proper alignment and fit.
3. Make any necessary adjustments to the pipe lengths.

5. Install the New Trap

Once you’re satisfied with the fit, follow these steps to install your new trap:

1. Apply PVC primer and cement to the joints of your new assembly.
2. Quickly press the pieces together, holding them in place for a few seconds to allow the cement to set.
3. If necessary, attach the new trap to the wall drain using a reducing coupling. Before connecting them, apply primer and cement to both the coupling and the pipe.
4. Use pliers to tighten the compression fitting that connects the trap to the sink drain.

6. Test for Leaks

Now that you’ve installed your new sink trap, you’ll need to check for leaks. Here’s how:

1. Fill the sink with water.
2. Place a paper towel directly beneath the new trap inside the cabinet.
3. Pull out the sink drain plug, allowing all the water to rush out.
4. Check the paper towel for any wet spots that indicate a leak.

If you notice any leaks, tighten the connections or reassemble the affected sections as needed.

Identifying the Right PVC Sink Trap Size

Choosing the correct PVC sink trap size ensures a successful replacement. Standard sizes for kitchen sinks are usually 1 1/2 inches in diameter, while bathroom sinks typically have traps that are 1 1/4 inches. Measure your existing pipes to confirm compatibility with the new trap assembly you purchase. Installing the incorrect size can lead to improper sealing and potential leaks.

Troubleshooting Common Issues with PVC Sink Traps

Even with careful installation, you may encounter some challenges. Here are some common issues and their solutions:

• Improper slope: To create proper water flow, the horizontal pipe should slope slightly downward toward the wall drain. If the slope is incorrect, adjust the pipe alignment accordingly.
• Misaligned pipes: If the new trap doesn’t align perfectly, use flexible coupling to make minor adjustments. These couplings provide some flexibility and can help achieve a snug fit.
• Persistent leaks: Double-check all connections and confirm proper primer and cement application. Sometimes, disassembling and reapplying the cement can resolve the issue.

Preventive Maintenance Tips for Your PVC Sink Trap

Regular maintenance can help prolong your PVC sink trap’s lifespan and prevent future issues. Here are some preventive maintenance tips to keep in mind:

• Avoid using harsh chemical drain cleaners that can damage PVC. Instead, clear your pipes using natural cleaning solutions like baking soda and vinegar.
• Clean the trap regularly to prevent debris buildup. Debris can cause blockages, which can lead to leaks or reduced water flow.
• Periodically check for leaks, especially after moving items under the sink. Catching small leaks early can prevent more significant problems down the line.

Our Conclusion

Replacing a PVC sink trap is a straightforward DIY project that can resolve leaks and improve your sink’s drainage. With the right tools and careful attention to detail, you can complete this task in a few hours, saving money on professional repairs and gaining valuable home maintenance skills.

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