How to Prevent Tankless Water Heaters from Freezing

The best tankless hot water heaters are designed to provide a continuous stream of hot water, on-demand, to any faucet, tap, or water-using appliance in the home. That process cannot be completed if the water lines freeze.

One of the unique challenges that tankless heater owners face is water loss that occurs from frozen pipes. Tank-based systems rarely face such an issue because of the indoor nature of the system.

If you live in a geographic location which experiences hard freezes on a regular basis, then here are some of the steps you can take to prevent your tankless water heater from freezing up on you during the winter.

Option 1: Install your new system in a heated location

If your tankless water heater is installed in a heated space, then you will prevent most freezing issues that could occur with your system. Should that not be possible, a sheltered location outdoors can prevent many freezing issues as well. Place your vents away from where prevailing winds hit your home. Build a small lean-to structure to protect the unit. Incorporate vent terminations to provide additional wind resistance.

Option 2: Remove any standing water

Even tankless systems can develop standing water inside of them. If the weather is cold enough, then this water will freeze over time. Once that water turns to ice, the internal components of the water heater face a higher risk of damage. By draining the unit, especially if you will be away from home for 48 hours or more during the winter, you’ll remove the standing water that could freeze.

Note: Some tankless systems come equipped with a built-in electric heater that is designed to prevent freezing. These heaters require a power source to operate. If you lose power and are away from home, the unit may experience freeze damage.

Option 3: Keep an uninterrupted power source available

Freeze protection systems operate when power is supplied to them. If you cannot drain the system, consider installing an uninterrupted power source that will supply electricity to your protection system during a power outage. This is especially important for homes that experience frequent or rolling power outages.

Look for drain-down solenoids or a battery backup as your best solutions in this area.

Option 4: Install a recirculation system

If your tankless water heater is compatible with a recirculation system, then consider installing one if you live in a colder climate. These systems make hot water available instantly. During the winter, this system will keep the plumbing system in your home warmer, which greatly reduces the risk of freezing. In extremely cold temperatures, a freezing incident is still possible, so consider this option one step toward prevention instead of a catch-all solution.

Option 5: Insulate your system

Insulating your tankless water heater will help to prevent freezing from happening within the unit. Take the time to insulate your pipes as well, especially if they are in a location that is exposed to low levels of protection. Attic-based and crawlspace-based pipes tend to be the most vulnerable. Use a heat tape, fiberglass insulation, or a polyethylene wrap for the best results.

In regions where a hard freeze is common before November 1, all plumbing may need to be insulated in the home.

Note: Pipe insulation should be used with an electrical freeze prevention method, such as a heater, to reduce freezing risks in excessively cold geographic locations.

Option 6: Keep your plumbing system active

Running water freezes slower than water that is standing still. If you’ve used the above options and are still concerned that a freezing event may occur, then run a small amount of water through your system during the overnight hours. Just 1/10 of a gallon, per minute, can be enough to keep most standard-sized pipes from freezing in the average home.

You only need to turn on one fixture. Just make sure it is the one that is furthers from the actual tankless heater.

The greatest freezing danger to a tankless hot water heater is standing water that expands within the unit itself. This danger can apply to indoor models that are placed on an exterior wall. It is more common, however, with outdoor installations.

By keeping the unit warm, most freezing incidents can be prevented. During a period of excessive cold, use these additional options in combination with each other to ensure that the water won’t freeze and damage your new tankless water heater.

Freezing is just one potential problem, for more troubleshooting tips read on here.

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Greg Mattson

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