A hand with a wrench installing a heat pump water heater with the text DIY! in blue glowy font.

Installing a heat pump water heater on your own can save you a lot of money on labor. The process is similar to installing a traditional water heater tank. Still, there are a few key differences you should know. What are they?

To install a heat pump water heater:

  • Remove the old unit
  • Use channels to prop the heat pump water heater six inches from the wall
  • Plumb the water inlet, drain line, and gas line to the new unit
  • Purge the water lines
  • Wire and test the unit

In this article, I’ll explain everything about installing a heat pump water heater. I’ll also go over the differences and similarities between installing a heat pump water heater and a traditional water heater tank, so keep reading!

1. Remove the Old Water Heater

Removing the old water heater is the first step. Here’s how it’s done:

  1. Turn off the water inlet and outlet.
  2. Close the gas line if you have a gas-powered water heater.
  3. Flip the circuit breaker that’s powering the unit.
  4. Drain the old water heater to remove all the water.
  5. Remove the retaining bracket and dispose of the tank.

I recommend connecting a garden hose adapter to the drain outlet for a more efficient draining process.

Run the hose to get rid of the water. I suggest you contact your city if you’re considering draining water into the sewage system.

A technician adjusting the settings of a heat pump water heater
Before installing your new heat pump water heater, the old one has got to go!

Oh, here’s something to keep in mind. If you don’t close all the water lines, gas lines, and electrical circuits, you’ll flood the house and create a hazard zone.

Only try to remove an old water heater once you can shut off everything going to it.

2. Use Channels To Prop the Heat Pump Water Heater

Construction channels are perfect for propping a heat pump water heater.

Most building codes recommend keeping the water heater at least six inches from nearby walls for ventilation, water expansion, and overheating prevention.

Check your owner’s manual for the exact distance requirements for your heat pump water heater.

To prop your heat pump water heater, place a three-inch thick styrofoam pad under the new water heater if it’s on a concrete floor.

If installing the heat pump water heater on wooden floors, put a drain pan under it to prevent condensation, wood rot, and wood expansion.

Due to these minor space adjustments, you’ll likely have to change the plumbing for your new water heater.

Important Reminder: Some states require straps around the water heater. Most of these states are earthquake zones, so the straps are essential to secure the heater.

3. Plumb the Water Heater and Drain

Follow these instructions to plumb the new water line and drain for your heat pump water heater:

  1. Use the same plumbing dimensions as your current water heater unless otherwise noted by the manufacturer.
  2. Run the drain line to the same drain location as your old water heater.
  3. Extend the new plumbing line if necessary. Suppose the old water heater has the same footprint, placement, and inlet or outlet locations. In that case, you may only need a little extension.

Your heat pump water heater might have different plumbing inlets and outlets than your current unit.

For example, many A.O. Smith heat pump water heaters have their plumbing on the right side, as opposed to the top inlets and outlets on their old-school water heaters.

4. Fill the Tank With Water

Filling a heat pump water heater is one of the easiest parts of the process. All you have to do is hook up the water line wherever it goes on the heater, then open the water valve.

That said, you can do a few things to speed up the process.

  • Don’t close the pressure relief valve before filling the tank. Doing so adds a bit of resistance.
  • Turn off all other water sources going through your house. You need to direct as much pressure into the heat pump water heater as possible.
  • Close the drain valve on the water heater. This one might seem obvious, but many overlook this step during installation!
A woman with her finger under a stream of water coming out of a hot faucet waiting for hot water to arrive.
Make sure your water isn’t running when filling the new heat pump water heater!

Once you’ve finished filling the tank, here are a couple more tips:

  • Leave the water line open when filling the tank. It can stay open for the remainder of the installation process.
  • Don’t turn on the water heater or wire it right after filling the tank. Most heat pump water heaters require a short expansion period and a purging process to get the air out of the lines.

5. Purge the Air From the Water Lines

Your heater pump water heater will have a lot of air in it because it was empty for so long. As a result, the water lines will have plenty of bubbles.

Fortunately, it’s very easy to purge the air from the lines and prevent structural damage to your plumbing system.

Here’s what you should do:

  1. Open all the water lines throughout your house.
  2. Wait until each line has a steady stream of water that doesn’t skip or have too many bubbles.
  3. Close each water source, then open them again, checking for bubbles.
  4. Repeat the process until all the air is out of the water lines in your home.

Failure to purge the air out of the water lines will cause pressure buildup in the heat pump water heater. Not only can this permanently damage the unit, but it can also drastically limit the water pressure going through your home.

It’ll also reduce the temperature adjustments the water heater applies, so it’s bad news all around.

Here’s a helpful YouTube video detailing how you can purge the water lines when installing a heat pump water heater:

6. Wire Your New Heat Pump Water Heater

Wiring your new water heater is relatively straightforward. Red goes to red, black goes to black, and green goes to the ground terminal.

Some heat pump water heaters have copper grounding wires that connect to a nearby grounding location separate from the unit. Still, you can use the same grounding wire as your old water heater.

Wiring your new heat pump water heater doesn’t have to be nearly this complicated!

If you need a hand deciding which unit is right for you, review our helpful heat pump water heater guide. It’ll help you weigh the pros and cons of each water heater style and how they’re wired and plumbed into your home.

7. Install the Pressure Relief Valve

Much like filling the tank, installing the pressure relief valve is a very easy process. Most pressure relief valves screw into the heat pump water heater. Twist the valve onto the water heater’s labeled relief valve female inlet, and you’ll be good to go.

Keep in mind that some pressure relief valves require a roll of plumber’s tape. The manufacturer will let you know if you need this tape in the instructions. Wrap the tape around the pressure relief valve’s threads for a long-lasting waterproof seal.

Green Building Advisor explains that not adding a pressure relief valve can explode your heat pump water heater. It’ll scorch everything in sight, costing you thousands of dollars in repairs!

This simple, few-second process is a money saver in many ways. The built-up heat and steam leave through the valve instead of expanding the tank.

8. Turn On the Water Heater

Once everything is installed, plumbed, wired, and filled, you can turn on the water heater. Follow these steps:

  1. Flip the circuit breaker, then check if the water heater starts humming.
  2. Set the desired max temperature.
  3. Give your heat pump water heater a few minutes to warm up before turning on the water sources in your home.

Heat pump water heaters are quite efficient because they provide a steady source of heated water. However, it takes a little while for the first several gallons to heat up because it’s likely the same temperature as the water from the water line.

When the water heater’s pilot light or electrical switch stops running, your water heater is ready to use. Turn on a couple of sinks or showers in your home and adjust the max water temperature to your liking.

Important Reminder: Many heat pump water heaters have multiple heating modes. Check your water heater’s manufacturer guidelines to learn more about the modes and determine which suits your preferences.

Remember to align and clean the filter every 90 days!

Final Thoughts

Once you install the unit, you’ll save plenty of money in the long run. Heat pump water heaters are worth it because they reduce energy bills, gas consumption, and more.

Sources

Green Building Advisor: Saving Sustainably: Installing a Heat-Pump Water Heater

This Old House: How to Install an Electric Heat Pump Water Heater

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