Frozen Water Line? How Deep Lines Are Buried in Northern Colorado and How to Thaw Them Safely

How to unfreeze water lines inside the house

These steps are for pipes you can see and reach: in a basement, a crawlspace, a garage or under a sink.

1. Find the frozen section. Pipes on exterior walls, in crawlspaces and garages, and under sinks on outside walls freeze first. Frost on the pipe, a bulge, or a faucet that only trickles helps narrow it down.
2. Open the faucet. Open both the hot and cold sides of the faucet the pipe feeds, so melting ice has somewhere to go and pressure can escape.
3. Apply gentle heat. Use a hair dryer, an electric heating pad, towels soaked in hot water, a space heater kept well away from anything flammable, or a heat cable rated for pipes and installed according to its instructions. Start near the faucet and work back toward the frozen spot.
4. Keep electricity away from water. Keep cords and dryers out of puddles, use a GFCI-protected outlet where you can, and never leave a space heater unattended.
5. Keep going until full pressure returns, then check every other faucet. If one pipe froze, others may have too.
6. If the pipe bursts, shut off the water. Close the main shut-off valve, usually where the water line enters the house, and open a faucet to relieve the pressure. Then call us.

What not to do. Never use a torch, a propane or kerosene heater, a charcoal grill or any other open flame. Flames can start a fire inside a wall or floor and damage the pipe, and fuel-burning heaters in a closed crawlspace can build up carbon monoxide.

How deep are water lines buried?

Deep enough to stay below the frost line, the depth to which winter freezes the ground. There is no single number for every property: building codes and the water utility set the required burial depth for a water service line, and in cold climates that depth puts the pipe below the frost line.

For reference, Larimer County requires foundations to have at least 30 inches of frost protection below grade. That figure is for foundations, not pipes. Water providers set their own cover requirements for service lines, and they can be deeper, so ask your water utility for the required depth rather than borrowing the foundation number.

Older lines do not always meet today’s rules. A line laid shallow, one under a driveway where frost goes deeper, or one where regrading or landscaping removed soil from above is more likely to freeze.

How deep to bury a water line

If you are installing or replacing a line, get the required depth from your water provider and the building department, and confirm it as part of the permit. In Fort Collins, replacing concealed pipe is new work that needs a plumbing permit, which costs $65 plus sales tax on the project valuation, and homeowners doing their own work file a homeowner affidavit. Call 811 before you dig.

Can sewer lines freeze?

It is uncommon. Wastewater is usually warmer than the surrounding ground, it flows in bursts that drain away, and building sewers are buried. Sewer pipes can still freeze when:

• The line is shallow, or runs through an unheated crawlspace or another exposed spot.
• Flow is low. A slow, steady trickle can freeze bit by bit in a cold section.
• The home is vacant with the heat off or turned way down, so nothing warm moves through the line.
• Water sits in a belly, a low spot where water stays put and can freeze solid.

The signs are drains that slow down or back up during a deep cold spell, often with gurgling. Do not pour chemical drain openers into a frozen or blocked line: they can sit in the pipe and splash back, and they should never be mixed. If sewage is backing up, stop running water and see emergency sewer repair. Active sewage backups are scheduled first. For more on sewer problems in general, see our guide to sewer line repair in Fort Collins.