Do Water Heaters Need Freeze Protection in Arizona?
Some do. Apache Junction's winter lows average about 42°F, but they have dropped into the high teens, with a record of 17°F. A heater inside the home is rarely at risk. Outdoor closets, mobile-home closets, wall-mounted tankless units and bare pipes on outside walls are, and higher towns like Superior get colder still.
Most winters bring only a handful of nights near freezing. Because they're rare, few homes here are built for them. Pipes run along outside walls, closets have gaps, and nobody thinks about the heater until a line splits at 6 a.m.
Water heater freeze protection here is mostly about the pipes and fittings around the heater, plus the small parts of tankless units. A full tank holds a lot of heat. The thin lines feeding it don't.
Where Freezes Hit Water Heaters Around Here
- Outside closets on mobile homes. Supply lines often come up from under the home, through skirting that lets cold air in.
- Outdoor and rooftop tankless units. The cabinet has freeze protection, but the pipes and valves below it are exposed.
- Exposed copper or PEX on exterior walls, often near a garage or a backyard heater closet.
- Lines inside uninsulated skirting on manufactured homes and park models.
- Condensate drains on condensing tankless units that end outdoors. A frozen drain can back up and shut the unit down.
Elevation matters too. Superior sits at about 2,890 feet and can cool off more at night than Apache Junction. Homes on the higher foothill side of 85119 with lines on outside walls can run a little colder too. If you live out that way, our page on water heater leaks in Superior and Queen Valley covers the local setups.
Insulating Lines, Closet Doors and Vents
Insulation is cheap and does most of the work. Slip foam pipe sleeves over exposed hot and cold lines, including the short runs between the floor and the heater. Wrap valves with insulation made to fit them. Seal gaps in skirting where pipes come through, so cold wind doesn't blow straight across them.
Closet doors are where people go wrong. Weatherstripping helps an electric heater's closet. On a gas heater, the louvers or vent openings in the door or wall supply the air the burner needs. Block them, and the burner burns poorly, the pilot can go out, and carbon monoxide can build up.
Safety: Never cover the air openings of a gas water heater's closet, even for one cold night. Never wrap the relief valve, block its discharge pipe, or cover the gas control or burner door. Insulate the pipes instead.
Our mobile home water heater page has more on how those outside closets are set up.
Tankless Freeze Protection Needs Power
Most outdoor tankless units have small built-in heaters that switch on when the cabinet gets cold. They only work with power. A tripped breaker, a GFCI outlet that has popped, or a power outage on a freezing night leaves the heat exchanger unprotected.
What should I do if the power goes out on a freezing night?
If the outage looks like it will last into the coldest hours, many manuals call for draining the unit: shut off the gas, close the isolation valves, open the drain plugs or valves the manual shows, and catch the water in a bucket. Steps differ by model, so keep the manual where you can find it in the dark. When power returns, close the drains, open the valves and let water run through before firing it.
Do the pipes under a tankless unit need their own protection?
Yes. The unit's freeze protection is inside the cabinet. The supply lines, valves and condensate drain below it need foam sleeves, and sometimes heat tape. If a unit has already cracked from a freeze, our tankless water heater repair page explains what's usually fixable.
Heat Tape: Useful, But Use It Right
Heat tape, or heat cable, can protect a short, exposed run that insulation alone won't. It's also a known fire risk when it's old, damaged or used wrong.
- Buy a product listed for use on water pipes, and follow its instructions exactly.
- Self-regulating cable is the safer type for most homes. Never overlap or cross a constant-wattage cable over itself.
- Plug it into a GFCI-protected outdoor outlet, not an extension cord.
- Only cover it with insulation if the maker says that's allowed.
- Keep it away from a gas heater's flue, burner area and vent.
- Check it each fall for cracks, scorch marks or a dead thermostat, and replace old cable rather than patching it.
If there's no outdoor outlet near the heater, adding one is a job for an electrician.
If a Line Froze or Split
- Stop the water. Close the cold valve above the heater, or the home's main if the split is before that valve. If you aren't sure which valve is which, see how to shut off a water heater.
- Turn off the heat source. Switch off the breaker on an electric tank, or turn a gas control to Pilot or Off.
- Don't use a flame. Never thaw pipes with a torch or open flame. A hair dryer on a frozen, unbroken line is the gentle option.
- Watch as it thaws. A split often only shows once the ice melts and water moves again.
- Call for the repair. A cracked fitting or pipe near the heater is usually a short repair, not a new tank.
Our water heater pipe leak page covers the fittings and lines that usually fail. For water spreading across a floor at night, our emergency water heater repair line is open around the clock.
Away in Winter? Notes for Snowbirds
Most seasonal residents leave in summer, but some travel over the holidays or split the winter between homes. If the house will sit empty through a cold snap:
- Leave an outdoor tankless unit powered so its freeze protection keeps working, or have it drained by the manual's steps if the power will be off.
- On a gas tank, "Vacation" keeps the water warm at a low setting, which also keeps an outdoor closet a little warmer. "Pilot" or "Off" means no heat at all.
- If you shut off power or gas to a heater in an exposed spot, shut off the water too, and ask about draining the lines.
- Ask a neighbor to look in the closet the morning after a hard freeze.
Our snowbird water heater checklist covers the rest of the close-up. And if you come back to a wet closet, our water heater leak repair in Apache Junction is open 24/7.
Water Heater Freeze Protection FAQs
How cold does it have to get before water heater lines freeze here?
Water freezes at 32°F, but exposed pipes usually need several hours below that, and wind makes it worse. In our area, the nights to watch are forecasts in the mid-20s or lower, especially for lines on outside walls, in skirting or under an outdoor tankless unit. A brief dip to freezing at dawn rarely does damage to insulated pipes.
Should I let a faucet drip on a freezing night?
It can help. Moving water is slower to freeze, so a thin, steady drip from the faucet fed by the most exposed line lowers the risk. Open both hot and cold if both lines run past the cold spot. The water cost for one night is small next to a split line, but insulation is still the better long-term fix.
Can the tank itself freeze in an outdoor closet?
Rarely, if the heater is running. A full tank that's being kept hot holds plenty of heat for a cold night. The risk rises when the heater has been off for a while, during a long power outage on an electric tank, or in a closed-up home with the gas shut off. The thin supply lines freeze long before the tank does.
Is it safe to put a space heater in a water heater closet?
We don't recommend it. In a gas heater's closet, a space heater competes for air, sits near the burner and can be knocked into stored items. In any small closet, it's a fire risk left running overnight. Foam pipe sleeves, sealed skirting and listed heat cable on exposed runs are safer ways to protect the lines.
How can I tell if my outdoor tankless unit froze?
Common signs are no hot water and an error code after a cold night, little or no flow at the taps, or water dripping from inside the cabinet once it warms up. Don't keep restarting it. Turn off the power and gas, close the isolation valves, and have the heat exchanger and fittings checked before running it again.