Which pipes freeze
The Red Cross says the pipes that freeze most often are those "exposed to severe cold." In practice that means outdoor hose bibs, swimming pool and sprinkler supply lines, water pipes running through unheated interior spaces such as basements, crawl spaces, attics, garages and kitchen cabinets, and pipes running against exterior walls with little or no insulation.
Before the cold arrives
- Drain water from pool and sprinkler supply lines following the manufacturer's or installer's directions. The Red Cross is specific here: "Do not put antifreeze in these lines unless directed."
- Remove, drain and store outdoor hoses. Close the inside valve supplying each outdoor hose bib, then open the outside bib and leave it open, "so that any water remaining in the pipe can expand."
- Insulate exposed pipes in unheated areas, both hot and cold lines, using pipe sleeves or UL-listed heat tape or heat cable.
During a cold snap
- Keep the garage door closed if water lines run through the garage.
- Open kitchen and bathroom cabinet doors so warmer air reaches the plumbing underneath. Move cleaners and chemicals out of reach of children first.
- Let the cold water drip from any faucet served by exposed pipes. Moving water is far less likely to freeze.
- Keep the thermostat at the same temperature day and night. The Red Cross notes that this may raise your heating bill, but that it costs less than a burst pipe.
- If you are leaving for a stretch of cold weather, keep the heat on and set no lower than 55°F.
If a pipe is already frozen
The first sign is usually a faucet that produces only a trickle. Leave that faucet open: as the ice melts, running water helps clear the blockage. Apply gentle heat to the frozen section with an electric heating pad, a hair dryer, a portable space heater kept clear of anything flammable, or towels soaked in hot water. Keep the heat on until full pressure returns, and check your other faucets, since one frozen pipe often means others are frozen too.
Never use an open flame. The Red Cross is explicit: do not use a blowtorch, kerosene or propane heater, charcoal stove or any other open flame device. A blowtorch can bring the trapped water to a boil and burst the pipe.
If you cannot find the frozen section, cannot reach it, or cannot get it thawed, call a licensed plumber. For reference on what that call runs locally, askdoss reports emergency plumbing rates in the Milwaukee metro at $150 to $250 an hour against a standard rate of $95 to $150.
Sources
Every figure above comes from one of these. Where they disagree, the post says so rather than averaging them into a single number.