Frozen Pipe: How to Safely Thaw It Before It Bursts

Common Symptoms

• No water — or only a trickle — from a faucet during or after a cold spell
• Frost, ice, or condensation visible on an exposed pipe
• Pipe feels extremely cold to the touch and sounds hollow when tapped
• Only one faucet in the house has no flow while others work normally
• Faint bulge or crack visible on an exposed pipe section

Most Likely Causes

1. 1

   Exposed Pipes in Unheated Spaces (Most Common)

   Pipes running through unheated areas — crawl spaces, garages, exterior walls, attics, or uninsulated basements — are most vulnerable to freezing. When outdoor temperatures drop below 20°F (-6°C), uninsulated pipes in these spaces lose heat rapidly. A single night at low temperatures is sufficient to freeze a pipe that lacks adequate insulation or heat tape.

2. 2

   Pipes Along Exterior Walls

   Supply lines routed inside exterior walls with inadequate insulation can freeze during cold snaps. The wall cavity channels cold air from outside toward the pipe. This is especially common in older homes where plumbing was run through exterior walls without foam insulation to protect the pipe from the wall cavity's cold air column.

3. 3

   Loss of Heat in the Home

   A furnace failure, power outage, or thermostat set too low during absence can drop interior temperatures to the point where even interior pipes freeze. If the home has been empty for several days during a cold spell and the heat was off or failed, any pipe — not just exterior ones — can freeze.

4. 4

   Cabinet Doors Blocking Heat

   Under-sink supply lines in kitchen and bathroom cabinets can freeze when exterior walls are very cold and cabinet doors are kept closed, preventing warm room air from reaching the pipes. This is especially common for kitchen sinks on exterior walls in northern climates during prolonged cold spells.

Quick DIY Checks

1. 1Step 1 — open the faucet and locate the frozen section: open the affected faucet fully (both hot and cold handles if applicable) — this relieves pressure as ice thaws and gives you confirmation that water has begun flowing again. Starting from the faucet, work backward along the pipe toward the area where the pipe is exposed to cold. Look for the section that feels coldest, has visible frost or condensation, or is in an unheated area. If the frozen section is inside a wall, you will feel little or no water pressure change while thawing — the crack or freeze point must be inferred from the pipe's path through cold areas.
2. 2Step 2 — shut off the main water supply if you suspect a crack: before applying any heat, inspect the frozen pipe carefully with a flashlight. Look for: a visible split or crack in the pipe, a bulge or deformed section, or water staining around the pipe from a prior leak. If you see any of these signs, do NOT attempt to thaw the pipe — shut off the main water supply immediately and follow the [Burst Pipe Emergency](/fixes/burst-pipe-emergency) guide. A cracked pipe will release a pressurized stream the instant the ice plug melts. If the pipe looks intact and has no visible damage, it is safe to proceed with thawing.
3. 3Step 3 — thaw with a hair dryer or heat gun (never open flame): starting at the open faucet end and working TOWARD the frozen section, apply heat from a hair dryer on its highest setting or a heat gun on its lowest setting. Hold the dryer 6–8 inches from the pipe and move it slowly back and forth along a 6-inch section. Do not focus heat on one spot for more than 30 seconds — this can superheat water trapped behind the ice. Work in slow passes. The faucet is your progress indicator — once you see or hear a trickle of water, you have broken through the ice nearest the faucet; keep working further along the pipe toward the frozen section. Thawing a typical 12–18 inch ice plug takes 20–40 minutes.

Repair vs Replace

Recommended Tools & Parts

• Wagner Spraytech 0503067 Heat Gun

  Dual-temperature (750°F / 1000°F) heat gun for controlled pipe thawing. More powerful than a hair dryer, with enough heat to thaw a pipe quickly while maintaining safe working distance. Use on the lower 750°F setting for pipe thawing to avoid overheating the pipe surface.

  $20–$35

  Buy on Amazon →

• Frost King SP42/6 Foam Pipe Insulation

  Pre-slit foam pipe insulation tubes for 1/2-inch or 3/4-inch pipes — slides over existing pipes without fittings. 3/8-inch wall thickness provides effective freeze protection for interior pipes. Pack of 6 covers 36 linear feet. Essential follow-up after any frozen pipe event.

  $8–$15

  Buy on Amazon →

• EasyHeat ADKS-300 Self-Regulating Heat Cable

  UL-listed self-regulating heat cable for extreme cold protection on exposed pipes. Automatically increases heat output as temperature drops and reduces output when warm — energy efficient and safe. Rated for use under pipe insulation. Use on crawlspace, exterior wall, or garage pipes most vulnerable to freezing.

  $25–$55

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

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