Architectural Home Designs & Decorating Ideas

Step-by-Step Guide to Plumbing a Double Kitchen Sink

Gabriela Connell
4 minute read

Installing the plumbing for a new double kitchen sink may seem daunting, but it can be broken down into straightforward steps. Proper drain assembly is key to allow water to flow smoothly down the drain and prevent leaks.

With some basic tools and supplies, and by following the steps below, you can have your new double sink drain working properly in no time.

Things You’ll Need for the Project

Before starting any plumbing project, it’s important to gather all the necessary materials. Here are the basic components you’ll need to plumb a double kitchen sink drain:

double kitchen sink plumbing diagram

Having all these supplies on hand will make the installation process go smoothly.

Preparing the Sink for Installation

Before you can install the new plumbing, you need to securely mount the sink. Here are the steps for proper sink prep:

Removing the Old Sink

If you’re replacing an existing sink, remove the old sink first by disconnecting all the plumbing, cutting any silicone sealant with a utility knife, and lifting the sink out.

Installing the New Sink

Set the new double sink into the countertop opening and make sure it is level and aligned correctly. Apply plumber’s putty around the rim of the sink to seal it to the countertop. Follow the manufacturer’s instructions for any clips or mounting hardware to secure the sink.

Connecting the Tailpiece to the Sink

The first step in assembling the drain is to connect the tailpiece. This is the curved piece of pipe that fits into the sink drain opening.

To connect the tailpiece:

  1. Slide the tailpiece up into the drain outlet of the sink.
  2. The tailpiece will fit into the sink drain using a slip joint. This means the curved end slides into the drain opening.
  3. Slip the slip joint nut over the straight end of the tailpiece.
  4. Tighten the nut by hand to secure the tailpiece to the sink drain.

The tailpiece is now firmly attached to the sink drain and ready to connect to the p-trap.

Installing the P-Trap

The p-trap is a critical component of the drain assembly. It creates a “trap” of water that blocks sewer gases from coming up through the sink. Proper installation is key for it to function correctly.

Connecting Tailpiece to P-Trap

Use a slip joint elbow to transition from the vertical tailpiece to the horizontal p-trap. Insert the ends of the tailpiece and p-trap into the elbow. Tighten the slip nuts over the joints to secure the connection.

Aligning the P-Trap

Position the p-trap so it curves up before angling back down. This creates the water trap to block gases. The p-trap should be secured to the wall or cabinet with a strap to prevent sagging and maintain the proper trap shape.

Connecting the Drain Pipes

Extend the drain line from the p-trap using lengths of pipe, couplings, and elbows:

  1. Attach a short section of pipe to the p-trap arm with a coupling.
  2. Use elbows as needed to transition from horizontal to vertical.
  3. Measure and cut pipe to the needed lengths.
  4. Use couplings to join each section, tightening the slip nuts by hand.

The goal is to slope the pipes down towards the main drain line in the wall or floor. All joints should be tight to prevent leaks.

Tips for Proper Drain Alignment

Create Downward Slope

The drain pipes must slope slightly downward so water can flow freely towards the main pipe. Install them at a 2-3 degree downward angle.

Use Elbows to Transition

Use elbow fittings to transition between horizontal and vertical orientations as needed.

Cut Pipes to Correct Length

Pipes may need to be cut to fit properly. Measure first and use a hacksaw and miter box for straight cuts.

Testing the New Plumbing

Once all the drain connections are complete, test the sink:

  1. Turn on the water and look for any leaks.
  2. Make sure water flows smoothly down the drain.
  3. Tighten any joints or connections if needed.

If no leaks or drainage issues occur, the new plumbing is ready for regular use!

Troubleshooting Problems

Slow or Clogged Drains

If water drains slowly, debris is likely clogging the drain pipes. Disassemble and clean the pipes to remove the clog.

Misaligned Pipes

Standing water in the sink indicates the pipes may not have the proper downward slope. Readjust pipes as needed.

Tighten any leaking slip joint nuts or couplings. For stubborn leaks, apply thread tape to the threads before tightening.

Following this comprehensive guide will ensure your new double kitchen sink has efficient, leak-free plumbing. Take it step-by-step and you can complete this project yourself.