Tankless Water Heater in a DFW Freeze: What to Do When the Power Goes Out
By the Plumbing Hands editorial team · Published November 9, 2026
Tankless Water Heater in a DFW Freeze: What to Do When the Power Goes Out. A tankless water heater's built-in freeze protection only works while the unit has power, so in a freeze with a long power outage the safe move is to drain it: Rinnai's procedure is to shut off the cold water and gas supply, disconnect power and open the hot and cold drain valves. In Dallas-Fort Worth the average first freeze comes around November 22.
A tankless water heater's built-in freeze protection only works while the unit has power, so in a freeze with a long power outage the safe move is to drain it: Rinnai's procedure is to shut off the cold water and gas supply, disconnect power and open the hot and cold drain valves. In Dallas-Fort Worth the average first freeze comes around November 22.
Decision guide
How to decide what happens next
Start by identifying whether the issue is isolated to one fixture or affects several drains. If the problem is spreading, includes dirty water, or risks property damage, treat it as urgent and request provider guidance.
Checklist
Before and during a freeze: protect a tankless water heater
A tankless water heater relies on electric power to run its internal freeze protection elements, so when electrical power drops during severe sub-freezing weather, taking active steps protects the unit from internal freeze damage.
Keep power connected to the unit whenever possible, because many models rely on internal electrical heating elements and sensors that prevent freezing only while continuously powered.
Insulate exposed water supply lines and pipe fittings leading to and from the unit, especially for exterior wall or outdoor installations.
Check vent and drain lines for snow or ice blockages that can restrict airflow or trap moisture inside the unit.
Be prepared early: in Dallas-Fort Worth, NWS climate data shows the average first freeze arrives November 22 and the average last freeze occurs March 12.
Check your specific model's owner's manual for exact manufacturer recommendations, because freeze protection features and draining steps differ by brand.
Verification
If the power is out for a long time in freezing weather
Shut off the cold water supply valve and the gas supply valve to the water heater.
Disconnect electrical power to the water heater.
Open the hot and cold drain valves to release trapped water inside the unit.
If you are not comfortable completing these steps yourself or notice the unit is already leaking, call a licensed plumber.
Local service-area guidance
This page is written for homeowners and property managers in Dallas-Fort Worth. Plumbing Hands helps homeowners request emergency plumbing service across Dallas-Fort Worth. Availability, pricing, credentials, and arrival details should be confirmed directly with the matched provider.
Freeze season
More freeze and burst pipe help for Dallas-Fort Worth
Official sources for “Tankless Water Heater in a DFW Freeze: What to Do When the Power Goes Out”
These official and manufacturer sources back up the guidance above. Use them to check a plumber's Texas license, see what a typical home policy covers, or read more on the specific problem before you approve work.
Check that the plumber who shows up holds a current Texas license before you approve work.
Common questions
Frequently asked questions
Does a tankless water heater have freeze protection?
Yes, many tankless units feature built-in electric freeze protection devices, but these features require continuous electric power to operate.
Should I drain my tankless water heater during a power outage?
During a prolonged power outage in sub-freezing weather, manufacturers like Rinnai outline a general draining procedure: shut off cold water and gas, disconnect power, and open the hot and cold drain valves to clear internal water.
When does Dallas-Fort Worth usually get its first freeze?
According to National Weather Service data for Dallas-Fort Worth, the average first autumn freeze occurs around November 22.
What is the quick decision?
A tankless water heater's built-in freeze protection only works while the unit has power, so in a freeze with a long power outage the safe move is to drain it: Rinnai's procedure is to shut off the cold water and gas supply, disconnect power and open the hot and cold drain valves. In Dallas-Fort Worth the average first freeze comes around November 22.
When should I call instead of waiting?
Call when water damage, wastewater, essential fixture loss, or repeated backup symptoms are present.
What should I do first during a plumbing emergency?
Stop the water source if safe, avoid using affected fixtures, protect people from contaminated water, and request help.
What should I do during an active leak?
Use the closest working shutoff valve, keep water away from electrical areas, and request leak help quickly if water keeps spreading.
When should a drain backup be treated as urgent?
Treat it as urgent when more than one fixture backs up, wastewater appears, or the problem blocks essential use.
