How to Protect Your Outdoor Tankless Water Heater

Tankless water heaters are for the most part, maintenance-free but there are a few things that can cause them to break, or shorten their life. To ensure you have years of reliable trouble-free hot water then you will need to protect your outdoor tankless water heater from a few common causes of damage.

The biggest risk to an outdoor heater is freezing, even the Best Outdoor Tankless Water Heater is prone to damage if exposed to extremely cold temperatures.

Other common causes of damage to a water heater are corrosion and limescale build-up caused by hard water.

Are Tankless Water Heaters Okay to Use in Cold Climates?

Tankless water heaters don’t store large amounts of water like tank water heaters. So they don’t waste energy keeping water hot when it is not needed, making them are ideally suited to cold climates.

However, because they only operate when in use they need to be insulated to prevent the small amount of water they do hold from freezing when not moving through the unit. This is why some tankless water heaters have electric freeze prevention. This is effective at preventing freezing in temperatures of -5 to -22 degrees Fahrenheit depending on which unit you go for.

What happens when a tankless water heater freezes?

If you allow your tankless water heater to freeze, you risk burst welds and pipes. When water freezes, it expands putting pressure on all the areas it is in contact with, causing damage to the pipes and the heat exchanger.

7 Tips to Protect Your Tankless Water Heater from Freezing

Prevention is the best strategy when it comes to dealing with a frozen water heater. so take the time to do these few things and protect your tankless water heater from freezing.

Choose the right tankless heater for your climate.

If you are replacing or installing a new water heater then the best thing you can do is look for a water heater that has inbuilt electric freeze protection. Brands like Rinnai water heater have a freeze protection feature that includes electric heating elements. So long as there is power to the unit, the water heater is protected from freezing.

Install your water heater in a space that is likely to stay warm all year.

Protect your tankless water heater from extreme cold, choose a location that is protected from strong winds and somewhere snow is not likely to build up.

Ideally, if you are in an area prone to extremely cold temperatures then you should try to install your water heater in a warm spot. And potentially an outdoor heater may not be your best option. Instead, you should consider an internal unit and install it somewhere like the basement.

Keep a small amount of water running through your tankless water heater.

If you are only likely to experience a real cold snap once in a while then this is an easy solution. Simply turn on a faucet and leave it running at a trickle, not fast enough to engage the water heaters ignition, but just enough flow to keep water flowing through it and prevent it from freezing up.

This does waste quite a bit of water so it is not something to consider a long-term solution.

Install a recirculating pump system.

One way to protect your tankless water heater is by setting it up in a recirculating system. A recirculating pump will store and circulate heated water back through the tankless heater, preventing the system from freezing. This may require some modifications to the plumbing in your home but it is worth it if you want to keep your tankless water heater from freezing this winter season.

Make sure you have a reliable power supply.

Make sure you have a good power supply for your tankless water heater. Many areas that get extreme cold, also experience regular power outages. If this is the case for you then consider a UPS connected to a larger battery or backup generator that will turn on when the power goes out. Not everything runs on a battery like Honeywell thermostats. Your inbuilt antifreeze is only going to work when the power is on at the heater unit.

Insulate your inlet and outlet water pipes.

Even if you have a tankless water heater with electric antifreeze, it will not protect the exposed pipes from freezing. This is why they should be insulated.

Often referred to as lagging, pipe insulation is typically made from a material that has low thermal conductivity such as foam, or fiberglass. added insulation is achieved by wrapping it with a reflective coating such as aluminum foil tape to keep the heat energy in and cold out.

In mild cold climates simply covering the pipes with insulation and wrapping them with metallic duct tape will be sufficient to prevent them from freezing.

If you live where it gets very cold, then you can incorporate heating wires and insulation. The wires actively heat the pipes, just enough to keep them from freezing.

The wires are taped to the pipe, covered in the insulation, and then the entire setup is wrapped with metallic duct tape. This is the best option if you want to be 100% sure your pipes will not freeze.

Drain your tankless water heater when not in use.

If you are going to leave your tankless water heater not in use at all over winter, drain it to prevent it from freezing. Your water heater will have isolation valves allowing you to turn off the water, and then open the drain valve, leave it open until all the water has drained from the unit.

Protect your Tankless Heater From Limescale Build up.

Here again, prevention is the best option to protect your tankless water heater, to prevent the build-up of limescale and other corrosive elements in your water heater, install a water filter and softener to your water lines. This will filter out and collect the lime before it gets to your heater. These filter setups are not too expensive, and they will greatly increase the life of your tankless water heater. Plus they will make your drinking water taste better.

Regularly Flush Your Tankless Water Heater

To remove limescale build-up from your tankless water heater you need to drain the entire unit, then pump vinegar through the system, this will dissolve any built-up limescale in the pipes or heat exchanger.

Doing this regularly will protect your tankless water heater from excessive limescale build-up that reduces the efficiency of the heater, and can shorten the life of the heater too.

Protect Your Tankless Water Heater From Overheating.

If your water heater does not have adequate ventilation, or items are stacked up against it preventing airflow, it may overheat. This is not only going to shorten the life of your unit, it is also a potential fire hazard.

So, make sure you have the correct ventilation system installed, and you do not store any boxes or other items near your tankless water heater.

Wrapping It All Up

Choose The Best Outdoor Tankless Water Heater you can afford. One with inbuilt antifreeze, then follow the few small suggestions above, you will have no problem in protecting your tankless water heater from damage. It will give you decades of reliable service.

Diego Martinez

Diego Martinez, with a Bachelor’s in Mechanical Engineering from MIT, has been a leading figure in maintenance and facilities management for 16 years. He joined our editorial team in 2020, sharing his expertise in preventative maintenance, system optimization, and energy efficiency. Diego’s previous roles include engineering manager in manufacturing and consulting for facility management. He has provided practical advice and problem-solving strategies for maintenance issues. He is an enthusiastic cyclist and volunteers in community tech education programs.

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