Protecting pipes and water supply during a cold snap
Learn which pipes freeze first, how to insulate them and keep water moving during a cold snap, and what to do safely if a faucet goes dry or a pipe bursts.
Water in a pipe can freeze when the air around it stays at or below freezing long enough, and the pipes most at risk are the ones with the least protection from that cold. Freezing water expands, which can crack a pipe. The damage often stays hidden until the ice melts and a leak appears, so prevention matters more than repair. The steps that protect a home are straightforward: keep cold areas warm, insulate exposed pipes, keep water moving in the most vulnerable lines and know what to do if the flow stops.
Some of these steps involve heat and electricity, so take care with them. Call a licensed plumber for any pipe repair, and a licensed electrician for a permanent heat cable.
Which pipes freeze first
Outdoor lines freeze first, so check hose bibs, irrigation lines, outdoor showers, pool supply lines and the supply lines to outdoor appliances. Pipes in unheated spaces such as crawl spaces, attics, garages and basements come next, and so does the main water line where it enters the house near the surface. Pipes in exterior walls and the supply lines under kitchen and bathroom cabinets on outside walls are at risk too, because cold air can reach them through thin insulation, gaps around the wall plate or an open cabinet space. Look at each place where a pipe runs close to an outside wall before a cold forecast arrives.
A useful habit is to walk the house once a year and note which pipes sit in unheated or exterior areas. A simple sketch of the water lines, marked with the places that need extra attention, makes it much quicker to act when a forecast warns of a cold snap.
Protect pipes before the temperature drops
Start with insulation. Foam pipe sleeves are inexpensive and easy to fit on exposed lines in basements and crawl spaces. Heat cable, sometimes called heat tape, can help with pipes that are hard to insulate, but it must be listed for this use, installed as the manufacturer directs and plugged into a properly protected outlet rather than an extension cord. A permanent heat cable should be installed by a licensed electrician. Seal gaps where pipes enter the house with caulk or foam, because cold air moving through openings can reach the pipes directly.
Keep the heat on in the house. Set the thermostat to the same temperature day and night, and keep the house no cooler than about 55°F (about 13°C) while you are away. Open cabinet doors under sinks on outside walls so warm room air reaches the pipes, and keep garage doors closed when pipes run through the garage. Before the cold arrives, disconnect garden hoses from outdoor faucets. If an outdoor faucet has a shutoff valve inside the house, close it and open the outdoor faucet so water can drain out of the line.
If a freeze is forecast and the house has a crawl space, look for gaps in the foundation and around pipe entry points, and seal them. Ask a licensed contractor before closing or changing foundation vents, since the right approach depends on the local climate and moisture conditions.
Keep water moving during a freeze
Running water is much harder to freeze than standing water, so let faucets served by exposed pipes drip during a hard freeze. A thin, steady stream from the faucet farthest from the main supply is usually enough, and it uses only a small amount of water. Keep the drip going for as long as the temperature stays below freezing. A drip alone does not guarantee protection in very cold conditions, so combine it with insulation and heat. Keep the water heater working as well, since hot water lines can freeze too.
When water stops flowing
If one faucet stops, check whether others also stop. A single dry faucet often means a frozen section of its supply line. Open the faucet, then warm the pipe carefully with a hair dryer, a space heater placed a safe distance away or towels soaked in warm water. Work from the faucet toward the frozen section, and keep the faucet open so meltwater can escape. Do not use an open flame, such as a propane torch, a kerosene heater or a gas stove, to thaw pipes. These can cause fires and create carbon monoxide hazards. An oven or grill should never be used indoors to heat a room. Keep hair dryers and space heaters well away from standing water and wet floors. If you cannot find the frozen section, cannot reach it, or the pipe will not thaw, call a licensed plumber rather than continuing to apply heat.
If several faucets are dry, check whether the main valve is closed, whether the water utility reports an outage or whether a well pump has lost power. If you find a burst pipe or water leaking from a joint, shut off the main water valve immediately, open the faucets to drain the lines and call a licensed plumber. After water returns, check fittings and joints for leaks, since a thawing pipe can crack without showing a leak until the pressure is restored.
Find the main shutoff valve now, while the weather is mild and the path to it is clear, and make sure every adult in the house knows how to close it. A burst line is far easier to contain when the water can be shut off quickly.