Under Sink Water Heater Installation: A Comprehensive Guide

June 7, 2023


Installing an under sink water heater is an excellent way to have hot water instantly available whenever you need it. However, with the installation process comes some challenges that may cause confusion. In this comprehensive guide, we will take you through all the steps required to install your under sink water heater seamlessly.

Step 1: Gathering Tools and Materials

Before you begin, it is essential to have all the necessary tools and materials. These will include:

  • Under Sink Water Heater Unit
  • Compression Fittings
  • Pipe Wrench or Pliers
  • Adjustable Wrench
  • Teflon Tape
  • Hot Water Supply Line
  • Sink Valves
  • Hole Saw or a Drill

Once you have all the required materials, you can proceed to the next step.

Step 2: Turn off the Water and Drain the Pipes

The first step of the installation process is to turn off the water and drain the pipes. To do this, turn off the shut-off valve connecting the cold water line. You also need to turn off the hot water supply under the sink and allow the pipes to drain.

Step 3: Installing Sink Valves

The next step is to install sink valves. These are used to connect the hot and cold water supply lines to the under sink heater unit. Before installing, remember to apply some Teflon tape to the threads to avoid leaks. You can then attach the sink valves to the appropriate lines.

Step 4: Install the Heater Unit

Now you can install the under sink heater unit according to the manufacturer's guide. To do this, you may need to make a hole on the cabinet's bottom or side depending on the unit's design. Mostly, the holes are usually 1 ¾ inches in diameter.

Step 5: Connect the Water Lines

After installing the heater unit, it is time to connect the hot and cold water lines. Again, apply Teflon tape to the pipe threads to prevent any leaks. You can then attach the compression fittings to the appropriate water lines.

Step 6: Testing the System

You can turn the water back on to test if the system is working as expected. Allow the heater to fill and heat the water before testing the hot water supply. Make sure there are no leaks and everything is working correctly.


Installing an under sink water heater can be challenging, but with proper guidance, it becomes a simple and easy process. By following this comprehensive guide, you can install your under sink heater system with ease and enjoy hot water supply whenever you need it.

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I enjoy designing and curating experiences both virtually and in 3-dimensional reality. I have a Bachelor of Architecture from the Illinois Institute of Technology and currently practice professionally, but I also manage a few other ventures.
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