How to Protect an Outdoor Tankless Water Heater

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If you own an outdoor tankless water heater, you’ve got every reason to worry every time winter approaches. Reason? Mr. Winter doesn’t look kindly upon plumbing systems, and as if this isn’t enough, most manufacturers don’t cover warranties against damages caused by freezing.

And although outdoor tankless water heaters have built-in protection against temporary winter temperatures, the protection can’t withstand long-term freezing temperatures. So to ensure that your unit stays in the proper condition, you need to heater a little extra care during cold seasons.

In this post, we’ll discuss how you can protect your outdoor tankless water heater from freezing. Stick around.

How to Protect the Water Heating System

1. Insulate Your Pipes

Covering the pipes attached to your outdoor tankless water heater using an insulation material is one of the easiest ways to cut costs associated with heating water in your household. Insulating prevents frozen pipes.

Exposed pipes work much harder to maintain heat and provide hot water, which is a necessity in the winter. Covering them with insulation solves this problem and helps cut down on your energy costs as well.

If your pipes end up freezing, thaw them by turning up the heat. If using metal pipes, get a plumber to thaw them for you.

2. Flush Your System

To keep your heating unit running perfectly and for the longest tie possible, you need to flush it out at least once a year. This helps to remove limescale and mineral buildup that can clog the unit and reduce its efficiency.

The buildup can also corrode the pipes making it difficult for the heater to heat your water.

3. Drain the water from the Water Heater

If going for a vacation, you need to drain the water from your heater. This is because you don’t want your water heater to rupture when the freezing water expands.

The same should happen in case of a power outage.

To drain the water successfully from your water heater, you need to:

  • Turn off the gas supply and the cold water supply.
  • Turn off the temperature control.
  • Disconnect electrical power.
  • Get a bucket and place it under the heater to catch the water.
  • Remove the drain caps from the cold and hot isolation valves.
  • Open the valves.
  • Remove the cold water inlet filter.

Another thing you can do to protect your water heater from freezing is to install solenoid valves. These valves automatically open and release water from the heater in case of a power outage.

4. Install Your Water Heater in a Sheltered place

Although it might be a little hard, try as much as possible to install your outdoor tankless water heater in a sheltered place. Keep it away from the cold, and it’ll be less likely to encounter freezing issues.

Place the vents away from chilling wind and incorporate vent terminations, as these will provide additional wind resistance.

5. Keep Your Water Heater Running

Always keep your water heater unit connected to a power source. This doesn’t mean that you keep it on all the time; just ensure that it’s always plugged in. If you live in areas with frequent power outages, get a battery backup system or drain down solenoids.

6. Consider a Recirculation System

Recirculation systems are specifically designed to make hot water instantly available. So if living in areas that experience cold climates from time to time, this system is the hack for you.

During winter, this system allows your water heater to pump warm water continuously into your home. As a result, the water pipes remain warm throughout and shield your tankless heater from freezing.

7. Run a Trickle of Water

Another method you can adopt to protect your outdoor tankless water heater from freezing is running a trickle of water overnight. Just running 0.1 to 0.2 gallons per minute overnight can keep most standard-sized pipes from freezing. Do so, and you won’t have to worry about waking up to a frozen outdoor tankless water heater.


The greatest danger for any tankless water heater is standing water expanding inside the unit. It exerts a force that can split your plumbing unit, hence the need to protect it and prevent this from happening.

Should your water heater freeze over, get a professional plumber to solve the issue. Avoid trying to do quick DIY solutions, as you can end up damaging the unit even more.