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How To Winterize A Tankless Water Heater And Protect The Plumbing System

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

There are a lot of benefits to using a tankless water heater, but one of the many things a lot of owners forget is to winterize their tankless water heaters just before the cold weather and freezing temperatures kick in. 

Failing to winterize your tankless water heater is one of the main reasons why so many people experience problems with their tankless water heater when they start it back up after winter.

So, if you want to avoid breaking your tankless water heater unit, then you will need to follow the below advice in order to protect your plumbing system! 

Do I Really Need To Winterize My Tankless Water Heater?

A lot of new tankless water heater units come with pre-installed technology and features that help protect it from freezing temperatures.

If you already have a tankless water heater made by Rinanni, Noritz, Bosch, AO Smith, and a range of other popular brands, then you are probably thinking  that you can just rely on the technology used in your unit – but you would be wrong. 

Despite the claims of each brand, you cannot rely on the unit’s free protection features to completely protect your unit. 

This is because your units need to run on electric power in order for this feature to work.

This means that you have to use a lot of energy just to protect your tankless water heater from breaking when it’s not in use. This can cost you a lot in utility bills. 

Not only that, but what happens in the event of a power outage? Your tankless water heater (see also ‘Richmond Tankless Water Heaters Review And Buying Tips‘) unit will be exposed to the elements until your power comes back on.

If you are without power for hours or even days, then your unit is doomed! 

So, follow our advice below to winterize your tankless water heater (see also ‘Why Hot Water Temperature Fluctuates In Tankless Heaters?‘) unit to protect it from freezing temperatures no matter what happens this winter! 

How To Winterize Your Tankless Water Heater

The main steps of preparing your tankless water heater for winter is to drain the unit and unplug it.

Doing this means that there will be no water in the unit’s pipes that can freeze and cause damage when the temperatures drop. 

So, let’s go through the steps so you can confidently winterize your tankless water heater (see also ‘How To Keep Your Tankless Water Heater From Freezing‘). 

First, you will need to switch off the power and gas supply of your unit. To switch off the gas, switch it to ‘OFF’ through the main valve on the supply line.

For the electricity, you should just unplug your unit from its power socket and make sure the power is switched OFF on the breaker panel.

This will be indicated on the display unit as it will go completely black and no lights will be lit up. 

So, switching the power off of your tankless water heater unit is super easy. However, there is still some water inside your unit that will need draining.

You must wait until your unit is cool before you attempt to drain it, otherwise you could end up exposing yourself to boiling water and suffer from serious burns. 

If you have been running your tankless water heater (see also ‘Gas Vs Electric Tankless Water Heater ‘) unit, then wait until it is cool before moving onto the next step. 

When your tankless water heater unit is cool and ready to go, you will need to shut the water supply to your unit off.

You can do this by finding the main water valve (see also ‘How To Loosen A Corroded Water Valve‘) and switching it to OFF. This will prevent any more water from entering your unit. 

Now, you will need to drain the system. Find the taps and open them up.

This will allow the system to drain itself and release the pressure from the unit’s plumbing system – but there are a few things you need to do first before you can empty out the unit’s water. 

You will need to first disconnect both the incoming and outgoing water pipes of the unit. Then, you will need to find the inlet water filter and remove it. 

Once all of this is done, grab a bucket and use it to collect all the water as it drains out of the unit.

Make sure that you get every single drop – some people may even recommend that you use an air compressor to use bursts of air to push out every single drop of water from inside the unit. 


Now that there is not a single drop of water left in your tankless water heater unit and it is completely disconnected from its power sources, it is completely winterized ready for the temperature and weather conditions of winter! 

Many tankless water heater owners prefer this method as it means they can save a fortune in utility bills.

Without having to power your tankless water heater unit all through winter just to prevent it from breaking, you can save so much money on power just by draining it and cutting off its power when you no longer want to use it for the season. 

Once winter is over, you can just connect it back together. 

So, it’s a very good idea to winterize your tankless water heater (see also our article on cold weather and tankless water heaters) unit before winter instead of leaving it powered to use its freeze protection features.

Instead of spending so much on utility bills through winter, follow the above steps to save yourself money and keep your unit in great condition! 

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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