How To Install Pex Pipe Under Bathroom Sink

How To Install PEX Pipe Under a Bathroom Sink

Installing PEX (cross-linked polyethylene) pipe under a bathroom sink is a plumbing project many homeowners can undertake with the right tools, materials, and a thorough understanding of the process. PEX offers advantages over traditional copper or galvanized steel pipes, including flexibility, resistance to corrosion and freezing, and ease of installation through the use of specialized fittings. This article provides a comprehensive guide to installing PEX pipe under a bathroom sink, covering everything from preparation and material selection to step-by-step instructions and essential safety considerations.

Before commencing any plumbing work, it is crucial to understand the local plumbing codes and regulations. These codes often dictate the permissible materials, installation techniques, and inspection requirements. Failure to comply with local codes can lead to penalties and necessitate costly rework. Furthermore, it may invalidate insurance claims in the event of a plumbing failure. Therefore, consulting with a local building inspector or plumbing professional is highly recommended before starting the project.

Safety is paramount when working with plumbing. Turning off the water supply to the bathroom sink is the first and most critical step to prevent flooding and water damage. The water shut-off valves are typically located directly beneath the sink or in the main water supply line entering the house. Once the water is shut off, open the faucet to relieve any remaining pressure in the pipes. Place a bucket or towels under the work area to catch any residual water that may leak out during the installation process.

Key Point 1: Gathering the Necessary Tools and Materials

Successfully installing PEX pipe requires a specific set of tools and materials. Having everything readily available before starting will streamline the process and minimize interruptions. The essential tools include:

PEX Cutter: A specialized tool designed to cut PEX pipe cleanly and squarely. Using a standard pipe cutter or saw can deform the pipe ends, making it difficult to create a secure connection.

PEX Crimp Tool or Expansion Tool: PEX connections are typically made using either crimp fittings or expansion fittings. A crimp tool compresses a copper ring around the PEX pipe and fitting to create a watertight seal. An expansion tool expands the PEX pipe before inserting the fitting, allowing the pipe to shrink back onto the fitting for a secure connection. The choice between crimp and expansion fittings depends on personal preference and the specific application. Crimp fittings are generally less expensive, while expansion fittings offer a slightly more robust connection.

PEX Crimp Rings or Expansion Rings: These rings are used in conjunction with the crimp or expansion tool to create the PEX connections. Ensure that the rings are the correct size for the PEX pipe being used.

Deburring Tool: A deburring tool removes any burrs or sharp edges from the cut end of the PEX pipe, ensuring a smooth and leak-free connection.

Adjustable Wrenches: Wrenches are needed to tighten the connections between the PEX pipe and the sink faucet and shut-off valves.

Measuring Tape: To accurately measure the required lengths of PEX pipe.

Marker or Pen: For marking cut lines on the PEX pipe.

Bucket and Towels: To catch any water spills during the installation process.

Safety Glasses: To protect the eyes from debris.

The required materials include:

PEX Pipe: PEX pipe is available in various sizes and colors. The standard size for bathroom sink plumbing is typically 1/2 inch. Red PEX pipe is generally used for hot water lines, while blue PEX pipe is used for cold water lines. White or grey PEX can be used for either hot or cold water.

PEX Fittings: A variety of PEX fittings are available, including couplings, elbows, tees, and adapters. Select the appropriate fittings based on the specific plumbing configuration under the sink. Brass or plastic fittings can be used, but brass fittings are generally considered more durable.

Shut-Off Valves: New shut-off valves may be required if the existing valves are corroded or malfunctioning. Quarter-turn ball valves are a popular choice due to their ease of operation and reliability.

Faucet Connectors: Flexible faucet connectors are used to connect the PEX pipe to the faucet tails. These connectors are available in various lengths and materials, typically braided stainless steel or reinforced PVC.

Pipe Straps or Clamps: To secure the PEX pipe to the wall or cabinet to prevent movement and strain on the connections.

Plumber's Tape (Teflon Tape): To seal threaded connections on the shut-off valves and faucet connectors.

Key Point 2: Step-by-Step Installation Process

With the tools and materials gathered, the installation process can begin. The following steps outline the procedure for installing PEX pipe under a bathroom sink:

Remove the Existing Plumbing: Carefully disconnect the existing plumbing lines from the faucet tails and shut-off valves. Use adjustable wrenches to loosen the connections, and be prepared for some residual water to drain out. Inspect the shut-off valves for corrosion or damage. If necessary, replace the valves with new ones. Wrap the threads of the new valves with plumber's tape before installing them.
Measure and Cut the PEX Pipe: Measure the distance between the shut-off valves and the faucet tails. Add a few inches to each measurement to allow for slight adjustments and bends in the pipe. Use the PEX cutter to cut the PEX pipe to the required lengths. Ensure that the cuts are clean and square.
Deburr the PEX Pipe Ends: Use the deburring tool to remove any burrs or sharp edges from the cut ends of the PEX pipe. This step is essential for creating a leak-free connection.
Connect the PEX Fittings: Slide a PEX crimp ring or expansion ring onto the end of the PEX pipe. Insert the PEX fitting into the pipe until it is fully seated. If using a crimp tool, position the tool over the crimp ring and squeeze the handles firmly until the tool clicks, indicating that the crimp is complete. If using an expansion tool, insert the tool into the end of the PEX pipe and expand the pipe according to the tool manufacturer's instructions. Quickly insert the fitting into the expanded pipe and allow the pipe to shrink back onto the fitting.
Connect the Faucet Connectors: Attach the flexible faucet connectors to the faucet tails. Ensure that the connections are tight but not overtightened. Wrap the threads of the faucet tails with plumber's tape before making the connections.
Connect the PEX Pipe to the Shut-Off Valves and Faucet Connectors: Connect the PEX pipe to the shut-off valves and faucet connectors using the appropriate PEX fittings. Ensure that all connections are secure and leak-free.
Secure the PEX Pipe: Use pipe straps or clamps to secure the PEX pipe to the wall or cabinet. This will prevent the pipe from moving and putting stress on the connections.
Turn on the Water Supply: Slowly turn on the water supply to the bathroom sink. Check all connections for leaks. If any leaks are detected, tighten the connections or replace the fittings as needed.

It's important to emphasize the need for precise measurements and careful execution at each step. A rushed or sloppy installation can lead to leaks and potential water damage. Double-checking each connection is paramount, especially before turning the water supply back on.

Key Point 3: Important Considerations for a Successful Installation

Beyond the basic steps outlined above, several other considerations can contribute to a successful and long-lasting PEX pipe installation under a bathroom sink.

Proper Support: PEX pipe should be adequately supported to prevent sagging and stress on the fittings. According to plumbing codes, PEX pipe should be supported every 32 inches horizontally and every 4 feet vertically. Use pipe straps or clamps designed specifically for PEX pipe to avoid damaging the pipe.

Avoiding Kinks and Sharp Bends: PEX pipe is flexible, but it can kink if bent too sharply. Avoid sharp bends that can restrict water flow and weaken the pipe. Use PEX elbows to create smooth, gradual bends.

Protection from UV Light: PEX pipe can degrade over time when exposed to direct sunlight or UV light. If the PEX pipe is exposed to sunlight, it should be protected with a UV-resistant covering or paint.

Compatibility of Materials: Ensure that all fittings, valves, and connectors are compatible with PEX pipe. Using incompatible materials can lead to corrosion, leaks, and premature failure of the plumbing system. Brass fittings are generally considered the most durable and reliable option for PEX connections.

Testing the System: After completing the installation, thoroughly test the plumbing system for leaks. Turn on the water supply and check all connections for drips or signs of water leakage. If any leaks are detected, tighten the connections or replace the fittings as needed. It is also advisable to monitor the plumbing system for a few days after the installation to ensure that no leaks develop over time.

In addition to these technical considerations, proper planning and preparation are crucial for a smooth and efficient installation. Before starting the project, take the time to thoroughly inspect the existing plumbing system and identify any potential issues. Make a detailed list of the required tools and materials, and gather everything before starting the work. Having a clear understanding of the installation process and being well-prepared will significantly increase the chances of a successful outcome.

While installing PEX pipe under a bathroom sink is a manageable project for many homeowners, it is important to recognize the limitations of one's skills and experience. If there is any doubt about the ability to complete the project safely and correctly, it is best to consult with a qualified plumbing professional. A professional plumber can ensure that the installation is done according to code and that the plumbing system is functioning properly, providing peace of mind and preventing potential problems down the road.

The information provided in this article is intended as a general guide and should not be considered a substitute for professional advice. Local plumbing codes and regulations may vary, and it is essential to comply with all applicable requirements. By following these guidelines and taking appropriate safety precautions, homeowners can successfully install PEX pipe under a bathroom sink and enjoy the benefits of this versatile and reliable plumbing material.