How to Replace a Bathroom Drain Assembly: A Step-by-Step Guide

Updated at: 29/05/2025

A clogged bathroom drain can quickly transform a relaxing sanctuary into a frustrating inconvenience. Standing water, unpleasant odors, and the potential for bigger plumbing problems are all too common consequences of a malfunctioning drain assembly. Fortunately, replacing a bathroom drain isn't as daunting a task as it might seem. With the right tools and a little patience, even a novice DIY enthusiast can tackle this common plumbing issue and restore their bathroom to its former glory. A significant amount of time and money can be saved by performing this simple repair yourself.

This guide offers a comprehensive, step-by-step approach to replacing your bathroom drain assembly, covering everything from gathering necessary tools and materials to properly sealing the new unit. We'll walk you through each stage, providing clear instructions and helpful tips to ensure a successful and leak-free installation. Let's get started with the detailed step-by-step process outlined below.

Preparation and Safety Guidelines

Tools Needed
  • Plumber's putty
  • Large channel lock wrench
  • Bucket
Safety Guidelines
  • Turn off the water supply to the sink or tub BEFORE starting any work. Failure to do so can lead to flooding.
  • Wear safety glasses to protect your eyes from splashing water or debris.
  • Use plumber's putty or silicone sealant to ensure a watertight seal around the new drain assembly. Improper sealing can cause leaks.

Step-by-Step Instructions

  1. Disconnect the Drain

    • Disconnect the drain handle from the faucet.
    • Remove the large nut on the bottom of the drain using a channel lock wrench.
    • Remove the drain assembly from the sink.
    Remove the drain assembly from the sink.Remove the drain assembly from the sink.Remove the drain assembly from the sink.
    Disconnect the Drain

  2. Clean and Prepare the Sink

    • Clean the old plumber's putty from the sink.
    Clean the old plumber's putty from the sink.
    Clean and Prepare the Sink

  3. Apply Plumber's Putty and Install New Drain Assembly

    • Apply new plumber's putty around the drain opening.
    • Insert the new drain assembly into the sink and tighten.
    Insert the new drain assembly into the sink and tighten.Insert the new drain assembly into the sink and tighten.
    Apply Plumber's Putty and Install New Drain Assembly

  4. Remove Excess Putty

    • Remove excess plumber's putty.
    Remove excess plumber's putty.
    Remove Excess Putty

  5. Install Drain Plug and Lever

    • Install the drain plug and lever.
    Install the drain plug and lever.
    Install Drain Plug and Lever

  6. Reconnect Under-Sink Components

    • Reconnect the drain assembly under the sink, tightening all connections.
    Reconnect the drain assembly under the sink, tightening all connections.
    Reconnect Under-Sink Components

  7. Test for Leaks

    • Test the drain to ensure no leaks.
    Test the drain to ensure no leaks.
    Test for Leaks

Read more: Fixing a Leaky Toilet Tank: A Step-by-Step Guide

Tips

  • Place a bucket under the drain to catch any water.
  • Be careful not to scratch your sink when removing old putty.
  • The plumber's putty doesn't need to be perfectly shaped; just create a seal.

Common Mistakes to Avoid

1. Cross-threading the drain parts

Reason: Forcing a connection when the threads don't align properly can damage the parts and create leaks.
Solution: Carefully align the threads and turn slowly, applying gentle pressure until the parts are securely connected.

2. Not using plumber's putty or sealant

Reason: Improper sealing allows water to leak around the connections, leading to damage and potential mold growth.
Solution: Apply a generous amount of plumber's putty or sealant to all joints and connections before tightening.

3. Over-tightening the nuts and connections

Reason: Excessive force can strip threads, crack the drain parts, and make it difficult to remove the assembly in the future.
Solution: Tighten nuts and connections firmly but avoid excessive force—use your hands initially then a wrench for only a few additional turns.

FAQs

What tools do I need to replace my bathroom drain assembly?
You'll typically need a basin wrench, adjustable pliers, screwdrivers (Phillips and flathead), plumber's putty, and possibly a pipe wrench depending on your drain setup. It's also helpful to have a bucket to catch water.
How do I know what size drain assembly I need?
Measure the diameter of your existing drainpipe opening. This will usually be 1 1/2 inches or 2 inches. Most home improvement stores clearly label their drain assemblies with the size.
What if I encounter leaks after replacing the drain assembly?
Leaks often indicate improper sealing. Check to ensure you've applied plumber's putty evenly and thoroughly around the flange of the new assembly. If the leak persists, you may need to tighten connections or consider a replacement gasket.