Plumbing Troubleshooting
Frozen Pipes in Houston: How to Prevent Them and What to Do If They Freeze.
Houston's plumbing isn't built for freezing temperatures — which is exactly why a hard freeze causes so much damage here. The steps you take before the freeze matter more than what you do after.
What's Going On
Understanding the Problem
Houston averages fewer than 20 hours per year below freezing, which means the city's plumbing infrastructure — and almost all residential construction — is built with minimal freeze protection. Pipes run in exterior walls without insulation, in unheated attics and garages, and sometimes below the slab without adequate protection from temperature. When a sustained hard freeze arrives (temperatures at or below 20°F for 12+ hours, as during Winter Storm Uri in February 2021), the city's water infrastructure and the plumbing in hundreds of thousands of homes are all vulnerable simultaneously. The problem isn't just frozen pipes — it's the burst that happens when they thaw, often hours or days after the freeze has passed, when homeowners assume the crisis is over.
Diagnosis
Common Causes
1Pipes in exterior walls without insulation
Houston homes are frequently built with water supply pipes routed through exterior walls to reach outdoor hose bibs, kitchen sinks on exterior walls, or bathrooms on the outer perimeter of the house. These walls have minimal or no insulation by local standards — adequate for Houston's typical winters, but not for a sustained hard freeze. When outdoor temperatures drop to the low 20s, pipe temperatures in those walls can reach freezing within hours.
2Pipes in unheated attic spaces
Many Houston builders run water supply lines through the attic rather than through the slab, which makes them accessible for repair but completely exposed to outside temperatures when the attic is unheated. During a hard freeze, attic temperatures can match outdoor temperatures within a few hours. Attic pipes are frequently the first to freeze and, when they thaw, the first to flood.
3Outdoor hose bibs and supply lines to exterior fixtures
Outdoor hose bibs are particularly vulnerable because they're by design on the exterior of the structure. Frost-free hose bibs are designed to drain water back from the spigot into the warm interior of the wall, but only if the attached garden hose has been disconnected. A hose left attached during a freeze prevents drainage and causes the hose bib — and the pipe behind it — to freeze.
4Pipes in garages and unheated spaces
A water supply line that runs through an unheated garage — to a utility sink, ice maker, or water softener — is at risk during any freeze event. Garages in Houston almost never have insulated walls and have large doors that are not airtight. The water supply lines in these spaces can freeze quickly in sustained below-freezing temperatures.
5Municipal infrastructure stress during multi-day freeze events
During the February 2021 winter storm, it wasn't just individual home pipes that froze — the municipal water system lost pressure systemwide as pipes froze throughout the distribution network. When pressure dropped or disappeared, homeowners who hadn't experienced any pipe damage in their homes still had no water. When the system came back online unevenly, the sudden pressure restoration caused pipes that had been sitting cold and brittle to burst. This systemic dimension is unique to Houston-scale freeze events.
DIY Troubleshooting
What You Can Try
Before the freeze: disconnect all garden hoses from outdoor hose bibs
This is the single most impactful preventive step and takes two minutes. A hose left connected traps water in the hose bib spigot, preventing it from draining back into the warm wall. During a freeze, that water freezes and expands into the pipe inside the wall. Disconnect every hose before temperatures drop to freezing.
Before the freeze: let faucets drip on vulnerable lines
A slow drip from a faucet on an exterior wall keeps water moving through the pipe, which resists freezing better than standing water. For a hard freeze event, leave both the hot and cold handles slightly open on faucets that serve exterior-wall pipes — the kitchen sink if it's on an exterior wall, bathrooms in corners of the house. A drip uses very little water (less than $2 worth over a 48-hour freeze) compared to the cost of a pipe burst.
Before the freeze: open cabinet doors under sinks on exterior walls
Opening the cabinet doors under kitchen and bathroom sinks on exterior walls allows the warm air from the house to circulate around the pipes. This simple step keeps the pipe temperature above freezing in most residential freeze events.
If a pipe freezes: do not use an open flame to thaw it
Never use a propane torch, heat gun at high setting, or any open flame to thaw a frozen pipe. The steam expansion inside the pipe can cause it to burst violently. Instead, use a hair dryer on low heat, electric heating tape, or warm (not boiling) water-soaked towels on the outside of the pipe. Work from the faucet end toward the frozen section, not from the frozen section inward.
If you suspect a frozen pipe, shut off the main water valve before attempting to thaw
Before you try to thaw any pipe, shut off the main water supply. A frozen pipe may already have a crack in it that hasn't yet released water because the ice plug is holding pressure. When the pipe thaws, that crack opens and water flows freely. If the main is off, you have a manageable amount of water in the lines rather than unlimited supply flooding the space.
Know When to Call
When to Call a Pro
Call ARG Plumbing at (832) 419-3411 if you can't locate the frozen section, if the pipe doesn't thaw within an hour of applying heat, or — most importantly — if the pipe has already burst. During a major freeze event like Winter Storm Uri, demand for plumbers in Houston exceeds supply dramatically. Call early, get on a schedule, and in the meantime follow the leak response steps: shut off the main water, turn off the water heater, and protect your property from water damage while you wait.
Pro Tip
If you have to leave your home during a multi-day freeze event, do not turn the heat off or down below 55°F, and shut off the main water supply before you leave. A vacant house with no heat and full water pressure is almost guaranteed to have at least one pipe burst during a hard freeze. Shutting off the main doesn't fully protect frozen pipes, but it limits the damage to the water already in the lines rather than unlimited flow from the city supply.
Hristo
Master Plumber · ARG Plumbing