Cold weather can be hard on plumbing, and water heaters are no exception. When temperatures drop below freezing, water in exposed supply lines, drain lines, or the heater itself can freeze and expand, potentially cracking pipes, fittings, or internal components. The risk tends to be highest for units in unheated garages, crawl spaces, attics, and exterior closets, as well as tankless models mounted on outside walls. Even homes in regions with generally mild winters can experience occasional hard freezes that catch homeowners unprepared. Taking a few preventive steps before cold weather arrives may reduce the chance of a frozen line, a burst pipe, or an interruption in hot water. This guide explains where freezing risks typically occur, the preparations that may help, and what to do if a freeze happens anyway, as part of practical seasonal water heater maintenance.

Understanding Where Freezing Risks Occur

Not every part of a water heating system is equally vulnerable. Identifying the weak points helps focus preparation where it is most useful.

Exposed Pipes and Unheated Spaces

Water supply lines running through garages, crawl spaces, attics, or along exterior walls are often the first components to freeze. A water heater in an unheated space may keep its own tank above freezing while it operates, but the cold water inlet and hot water outlet lines leading to and from it can still freeze, especially during extended cold periods or when water is not flowing. Small-diameter pipes and fittings near vents or gaps in the building envelope are particularly vulnerable.

Drain, Relief, and Condensate Lines

The temperature and pressure relief valve discharge pipe and any condensate lines on high-efficiency or heat pump units can also freeze where they run outdoors or through cold spaces. A frozen condensate line may cause some units to shut down as a safety measure. Relief discharge piping must remain open, so any freeze protection applied to it should never block or cap the outlet.

Texas learned this the hard way: Winter Storm Uri, February 2021

This is not a Minnesota problem that wandered south. In February 2021, Winter Storm Uri held Texas below freezing for days, knocked out power statewide and burst pipes in homes that had never been built — or insulated — with that kind of cold in mind. Water heaters in garages, attics, and exterior closets froze alongside the lines feeding them, and many families lost hot water long after the roads cleared. That week rewrote the Texas rulebook: a forecast in the teens is not a curiosity, it is a deadline.

So prepare the Texas way. Insulate the exposed lines in the garage and attic before the front arrives, know where your shutoff is, and plan for a power outage as part of the freeze, not a separate surprise — Uri took the heat and the electricity at the same time. If a line does freeze or burst, the questions Texans ask us after every freeze cover what to shut off first and what can safely wait for a thaw.

Preparing Tank-Style Water Heaters

Tank-style units are generally more tolerant of cold than tankless models while they are operating, but their connections and surroundings still need attention.

Insulating Pipes and Sealing Drafts

Foam pipe insulation on accessible hot and cold water lines may slow heat loss and reduce freezing risk. Sealing gaps around doors, vents, and wall penetrations in the space where the heater sits can help keep cold air out. For gas units, it is important not to seal or block combustion air openings, since the heater needs adequate air to operate safely. Insulation should also be kept clear of gas vents, burner openings, and controls, following the manufacturer’s clearance requirements.

Heat Tape and Supplemental Warmth

In colder climates, electric heat tape or heat cable listed for use on water pipes may provide additional protection for exposed lines. These products must be installed according to their instructions, since improper use can create a fire risk. Keeping a garage door closed during cold snaps or maintaining a modest temperature in the space may also help. Portable heaters should only be used according to their safety guidelines and kept well away from combustible materials and the water heater itself.

Preparing Tankless and Heat Pump Units

Tankless and heat pump water heaters have their own cold weather considerations. Understanding how they respond to low temperatures can help homeowners plan appropriately.

Built-In Freeze Protection on Tankless Units

Many tankless models include internal heaters that activate when temperatures drop, protecting the heat exchanger and internal water passages. This protection typically depends on electrical power, so a power outage during freezing weather may leave the unit vulnerable. The protection also may not extend to the external pipes connected to the unit. If a prolonged outage is expected in freezing conditions, draining the unit according to the manufacturer’s instructions is often recommended.

Heat Pump Performance in Cold Spaces

Heat pump water heaters draw warmth from the surrounding air, so their efficiency may decline when the space around them becomes very cold. Many models switch to backup electric resistance heating when temperatures fall below a certain point. This can help maintain hot water, but it may increase energy use during cold periods. Their condensate lines also need protection from freezing. Checking the manufacturer’s recommended operating temperature range can help determine whether the current location remains suitable through the winter months.

Planning for Absences and Extreme Cold

Extended absences and severe cold events increase the stakes. A little planning may help prevent damage while no one is home to notice a problem.

Vacation Settings and Draining

For short trips, many tank-style units can be set to a vacation mode that keeps water warm without full heating. For extended absences in a home that may not remain heated, some homeowners choose to shut off the water heater and drain it and the plumbing system to reduce freeze risk. Because draining and restarting involve specific steps, particularly for gas units and tankless models, following manufacturer instructions or seeking professional help is advisable.

What to Do if Lines Freeze

If hot water stops flowing during a freeze, a frozen line is one possible cause. Open flames, such as torches, should never be used to thaw pipes because of the fire risk. Gentle, indirect warmth may be used cautiously on exposed pipes, but if a pipe has cracked, water may flow once it thaws. Knowing where the main water shutoff is located allows a quick response if a leak appears, and a professional can assess any damage. Checking the area around the water heater and along exposed lines after a thaw may reveal leaks that were hidden while the pipes were frozen.

Kurt’s take: I am a grandfather, and I am bringing my grandkids into this trade — which means I think about a freeze the way a family man does, not just a plumber. A house without hot water in a Texas freeze is not an inconvenience; with kids and grandparents under one roof, it gets miserable and then unsafe in a hurry. My judgment, plain and simple: do the cheap preparation in October, not the expensive repair in February. Wrap the lines, test the shutoff with your own hands, and show somebody else in the house where it is. Preparation is a family job.

Staying Ahead of Cold Weather

Preparing your water heater for freezing temperatures may help reduce the risk of damaged pipes, interrupted hot water, and costly repairs, especially when the unit sits in an unheated space. Our team of water heater maintenance technicians at Rainstone Water Heaters can evaluate your system’s exposure to cold, identify vulnerable lines, and explain which protective steps may suit your home. We aim to help you prepare before cold weather arrives rather than react afterward, and we explain each recommendation so you understand its purpose. If you would like help getting your water heater ready for winter, we encourage you to reach out to our team.

If a freeze does catch your home, our first-minutes guide to handling a water heater emergency calmly covers the shutoffs and safety checks in order. And because a burst line rarely sends a warning letter first, it helps to know what a repair visit costs before you ever need one — the service call is $125, and it disappears entirely when the repair goes forward.

Thirty-eight years in the trade and 27 as a master plumber teach a man two things: diagnose before you sell, and clean up like you were never there — as clean as it was in the beginning, if not cleaner. That is how I run my crews, and it is how I write this blog. — Kurt Pinkerton, responsible master plumber, Rainstone Water Heaters