When a furnace or the power fails in a hard freeze, the plumbing sets the deadline. A frozen pipe is an inconvenience. A split one is a flood: University of Illinois Extension puts the loss from an eighth-of-an-inch crack at up to 250 gallons of water a day.
Which pipes freeze first
The American Red Cross lists the usual victims: outdoor hose bibs, swimming pool supply lines and sprinkler lines, supply pipes in unheated spaces such as basements, crawl spaces, attics, garages and kitchen cabinets, and pipes running along exterior walls with little insulation. The point where the water service comes through the foundation belongs on the list too.
The split does not have to be where the ice is. A 1996 study at the University of Illinois Building Research Council found that the common picture of ice simply pushing on the pipe wall is wrong. Ice first blocks the pipe, then further freezing presses on the water trapped between the blockage and a closed end such as a shut faucet, and the pipe gives way at that pressure. That is why an open faucet helps.
Before the house gets cold
- Open the cabinet doors under kitchen and bathroom sinks so room air reaches the pipes, and move cleaning products out of children’s reach while they are open.
- Keep the garage door shut if water lines run through the garage.
- Let cold water drip from a faucet served by exposed pipes. Even a trickle helps, according to the Red Cross. The utilities bureau in Howard County, Maryland, advises it when temperatures fall below 15°F and never with the water running unattended.
- Keep the thermostat at the same setting day and night. If you leave home in winter, the Red Cross says not to set it below 55°F.
- Shut the inside valve to each outdoor hose bib and open the bib outside so it drains.
If the house will be left unheated
A house that will sit without heat for days, or a cabin closed for the winter, should be drained. Purdue Extension’s guide to protecting plumbing in a winter power failure sets out the order:
- Shut off the water at the main valve, or switch off the well pump if it is inside the house.
- Open every faucet and leave it open until it stops running.
- Drain the toilet tanks and any spray hoses.
- Empty the sink and tub traps, or pour in propylene glycol antifreeze equal to the water each trap holds.
- Cut the power or fuel to the water heater and other water-using appliances before draining them, and put no antifreeze in any appliance.
Never use ethylene glycol, the car radiator kind, anywhere in a home water system. Purdue also does not recommend propylene glycol in the supply pipes themselves; it belongs only in drains, traps and toilets.
Thawing a frozen pipe
A faucet that gives only a trickle usually means a frozen pipe. Leave it open and warm the frozen section with an electric heating pad wrapped around it, a hair dryer, towels soaked in hot water, or a space heater kept well clear of anything that can burn. Work from the open faucet back toward the ice, so meltwater and steam have somewhere to go. Never use a blowtorch, a propane or kerosene heater, a charcoal stove or any other flame. Electric tools and standing water also make a shock risk, so keep cords and hands dry.
Know where the main shutoff is before starting, because a split often shows only once the ice melts. If the frozen spot cannot be found or reached, call a licensed plumber. One frozen pipe is a sign that others nearby may be frozen too.