Frozen pipes are a risk in this region, even though our winters are mild by northern standards. The pipes most at risk are the ones exposed to the outside or in unheated spaces: outdoor faucets, kitchen and bathroom cabinets on exterior walls, basements, crawl spaces, attics and garages. A burst pipe can do a great deal of damage in a few hours. This checklist takes about an hour, and it is best done in October or November.
Before the first freeze
1. Find your main water shutoff and test it. If a pipe bursts, this valve stops the flow. WSSC advises that you locate and operate your main shutoff in advance. If it is stuck or leaks when you turn it, have it replaced before you need it. 2. Shut off and drain outdoor faucets. Close the interior valve that serves each outdoor spigot, disconnect and drain hoses, and open the outdoor faucet so the water left in the line can drip out. DC Water gives the same advice. If there is no interior shutoff for a hose bib, leave the hose off and consider having one added. 3. Insulate exposed pipes. Wrap pipes in unheated basements, crawl spaces, garages and attics. DC Water suggests that if pipes are exposed to cold air, wrap them with insulation, and notes that even newspaper helps. Foam pipe sleeves are inexpensive and easy to fit. 4. Seal sources of cold air. DC Water recommends sealing drafty windows and doors and insulating walls and attics. Check crawl space vents and any gaps around pipes that go through an exterior wall. 5. Check for slow leaks. A dripping fixture or a wet spot may freeze first. Fix leaks before the cold. With every tap off, a moving water meter means a leak somewhere. 6. Know where your vulnerable pipes are. Rowhouses and townhouses often have kitchen or bath plumbing on exterior walls. Mark these on your mental map.
During a cold snap
- Keep the heat on. WSSC advises keeping indoor temperatures above 55 degrees to help prevent frozen pipes, including when you are away.
- Open cabinet doors so warm air from the room reaches the pipes behind them.
- Let a faucet drip. In an extended cold snap, leaving a faucet running on a trickle keeps water moving. DC Water suggests the faucet farthest from the main valve. The cost of the water is small compared with a burst pipe.
- Do not assume a vacation house is fine. If you are going away in winter, leave the heat on and ask someone to check the house. If the house will be empty for a long time, consider shutting off the main and draining the system, which is a job to do with a plumber's help.
If a pipe freezes
The warning sign is a tap that runs weakly or not at all, especially when it is very cold. If you suspect a frozen pipe:
1. Open the cold-water faucet nearest the frozen pipe. WSSC recommends this to relieve pressure and reduce the chance of a break. Water will flow through the pipe as it thaws. 2. Warm the pipe gradually. WSSC suggests a hand-held hair dryer. DC Water cautions against using an open flame and against anything that can make melted ice boil, because that can break pipes. Never use a torch. 3. Turn off the main if you find a crack or the pipe is leaking, and call a plumber. 4. If you cannot reach the frozen section (inside a wall, say), or you are unsure, call a plumber rather than trying to thaw it yourself.
If a pipe bursts
Shut off the main water valve. Turn off power to any wet area if you can do so safely and dry. Open a faucet on the lowest floor to drain the lines. Photograph the damage for insurance. Then call a plumber. Emergency calls are answered 24/7, and dispatch happens during our operating hours.
Who is responsible
WSSC says that it handles the street mains and connections up to the property line. If a pipe freezes or breaks on private property or inside a home, repair is the property owner's responsibility. Where the utility's responsibility ends differs by utility, so ask yours where it ends at your address.
Do it yourself or call a pro
Everything on the "before the first freeze" list is a DIY task, apart from replacing a stuck main shutoff or adding an interior shutoff to a hose bib, which is a plumber's job. If a pipe has burst, or you cannot find the leak, call.
This guide was last reviewed on October 15, 2026.