Water heaters freeze much less often than pipes in winter. Hot water flowing through a traditional water heater usually keeps it safe. But since a tankless water heater turns on only when you use hot water, it has inherently less protection. Here’s what to do when your tankless water heater is frozen, and how you can prevent this.
Why Do Tankless Water Heaters Freeze?
One downside to tankless water heaters is they are prone to issues during cold weather. However, some brands have built-in freeze protection. These include Rinnai, which adds ceramic heaters to protect internal parts when temperatures fall to near freezing. A temperature sensor is included as well; it turns the unit on until it’s no longer at risk. Rheem tankless water heaters also include built-in protection.
* However, even a model with built-in features is vulnerable if you lose power.
Steps to Thawing Out Your Tankless Water Heater
The most important thing to remember is—do not run a tankless water heater that has frozen.
It must be thawed out first, or you risk causing major damage. You’ll need to defrost the unit first, which requires the following steps:
- Check whether the water heater or just the pipes are frozen.
- Examine the inside of the heater for burst pipes (if this is the case, thawing out the unit will cause a big mess).
- If the heater is frozen:
- Turn off the power and gas/water shutoff valves.
- Disconnect the unit and move it to a warm area.
- If necessary, turn on a space heater near it.
- Open the drain valve to let melting water escape.
- Check for leaks in the unit and with external pipes.
- If the heater and pipes are in good condition, reinstall the unit and open the gas and water valves. Restore electrical power to the system.
*Do not set the unit to its highest heat level; if ice forms, heating elements can overheat and catch fire.
How to Protect Your Tankless Water Heater from Freezing
If cold weather is on the way, and your tankless water heater doesn’t have built-in freeze protection, you can still prevent it from freezing. One option is to install solenoid valves, which automatically drain the unit if there’s a power outage. The valves stay closed if there’s an electric current and open in the absence of one.
You can also manually drain the tankless water heater. First, turn off the cold-water supply, gas supply, and temperature control. Disconnect electrical power at the circuit breaker. Then open a hot water tap to relieve pressure on the unit. A bucket should be placed under the water heater next. It will contain water that escapes after you open the drain caps and the hot and cold isolation valves.
To winterize a tankless water heater for when you’re away:
- Turn off the gas supply.
- Turn off the water supply.
- Open the freeze protection solenoid valve.
- Open one or two hot water faucets.
- Remove the cold-water line inlet filter and, if there is one, the hot-water line plug or inline filter.
- Turn off the circuit breaker to protect the unit against surges or outages.
- Cover the vent intake and exhaust to prevent air flow issues.
- Insulate or wrap electric heat tape around pipes.
Call Village Plumbing and Air for Help
Ice can cause significant damage to a tankless water heater because there’s little room for it to expand. Not only can Village plumbing install a unit successfully. Our trained technicians can address freezing and other repair issues. We’ll make sure you never run out of hot water. To learn more about tankless water heaters, or request 24/7 emergency service if your tankless water heater is frozen, contact us on the web or call 713-526-1491.