What Size Drain Pipe Does My Bathroom Sink Need? Measure Yours Now

Having properly sized drain pipes is crucial for ensuring that your bathroom sink drains quickly and efficiently. A drain pipe that is too narrow or too large can lead to slow drainage, leaks, and clogged drains. Measuring your existing drain pipes is the best way to determine what size replacement pipe you need when installing a new sink or replacing old pipes.

With some simple tools and a bit of DIY plumbing knowledge, you'll be able to upgrade your drain pipes and prevent future clogs and backups.

Step 1: Remove the P-Trap Under the Sink

The P-trap is the curved section of pipe that connects the sink drain to the drain pipe in the wall. To measure your drain pipe opening, you'll first need to disconnect the P-trap assembly. This involves unscrewing the slip joints at both ends of the curved section.

Place a bucket under the area to catch any water in the trap. Loosen the slip nuts at both ends with pliers or a pipe wrench. Detach the tailpiece from the sink drain and the horizontal arm from the wall drain. Set aside all the washers, gaskets and nuts so you can reassemble later.

Tips for Removing the P-Trap

• Use latex gloves to protect your hands
• Have rags ready to catch drips or leaks
• Avoid over tightening slip joints when reassembling

Step 2: Use a Measuring Tool to Measure the Opening

Now that the P-trap is detached, you'll have a clear opening to measure the drain pipe diameter. Use either a soft measuring tape, a rigid ruler, or a special plumbing pipe gauge to measure the opening.

Make sure to measure the interior diameter rather than the exterior. Carefully insert the measuring implement into the opening. Account for any corrosion or mineral deposits inside older pipes when taking the measurement.

Record the measurement in inches. Standard bathroom sink drain sizes are often 1 1/4", 1 1/2", or 1 5/8" interior diameter. Matching this measurement is crucial for selecting a properly sized replacement pipe.

Getting an Accurate Measurement

• Clean out any gunk or buildup first
• Take measurements at several points along the pipe
• Note measurements in 1/8" increments

Step 3: Inspect and Measure the Drain Fittings

In addition to the main drain pipe, also carefully measure the fittings that connect the pipes. This includes the slip joint nuts, washers, and tailpiece that attach to the sink drain itself.

Use your measuring tape to note the length of the tailpiece. Check the diameter of the horizontal arm that extends to the wall drain. Inspect any elbow joints or vertical pipe sections as well.

Having all these measurements will allow you to purchase compatible replacement drain pipes and fittings.

Tips for Measuring Fittings

• Inspect washers and gaskets for wear
• Note lengths in 1/4" increments
• Take photos to remember configurations

Step 4: Select a Replacement Drain Pipe

With the measurements of your existing drain pipe and fittings in hand, you can now select a properly sized replacement pipe. Most home improvement stores stock pipes in common bathroom sink drain sizes.

Match the replacement drain pipe size directly to your measured diameter. If the existing pipe is very corroded or damaged, consider upsizing the new pipe by 1/4" for better drainage.

Be sure to also get compatible slip-joint washers, nuts, tailpieces, and other fittings in the same diameter as your new pipe.

Tips for Picking a Drain Pipe

• Consult manufacturer spec sheets
• Allow extra room for clogs
• Match water flow rate

Step 5: Install the New Drain Pipes

Once you have all the correctly sized components, installation is straightforward. Secure the tailpiece to the sink drain. Attach the trap arm to the wall drain. Slope pipes at 1/4" per foot.

Check for leaks and verify smooth drainage before reconnecting sink supply lines. Refer to the manufacturer's guide for detailed installation instructions.

Taking the time to properly measure and install a new drain pipe will prevent so many future headaches. No more slow sink drainage or stubborn clogs!

Common Questions about Bathroom Sink Drain Pipes

What size drain pipe is best?

The most common and recommended size for a bathroom sink drain pipe is 1 1/2 inches in diameter. This provides adequate water flow while still allowing for easy cleanouts.

How do I know if my pipe is clogged?

Signs of a clogged drain pipe include water pooling in the sink, gurgling noises, smelly odors, and slow draining. If you notice these issues, there may be a blockage in the pipes.

What is the maximum drain pipe length?

As a general rule of thumb, the maximum length of a horizontal drain pipe should be no longer than 10 feet. Longer pipes are more prone to clogging and drainage issues.

Measuring your bathroom sink drain pipe correctly is crucial for installing a replacement pipe that will provide optimal drainage. Carefully detach the P-trap and use a measuring tape or ruler to check the interior diameter.

Also measure all the connecting fittings and pieces. Select a new pipe that matches your existing size. A properly sized drain pipe will lead to a lifetime of clog-free bathroom sink enjoyment!