Extreme Cold – Tips to Protect Your Home

from the Wrentham Permanent Building Committee

With temperatures expected to reach -10°F Friday evening into Saturday morning, combined with blowing and drifting snow, conditions are right for those susceptible pipes in your home or business to freeze.

Why Pipes Burst
Surprisingly, ice forming in a pipe does not typically cause a break where the ice blockage occurs. It's not the radial expansion of ice against the wall of the pipe that causes the break. Rather, following a complete ice blockage in a pipe, continued freezing and expansion inside the pipe causes water pressure to increase downstream -- between the ice blockage and a closed faucet at the end. It's this increase in water pressure that leads to pipe failure. Usually the pipe bursts where little or no ice has formed. Upstream from the ice blockage the water can always retreat back towards its source, so there is no pressure build-up to cause a break. Water has to freeze for ice blockages to occur. Pipes that are adequately protected along their entire length by placement within the building's insulation, insulation on the pipe itself, or heating, are safe.

Mitigating the Problem
Water freezes when heat in the water is transferred to subfreezing air. The best way to keep water in pipes from freezing is to slow or stop this transfer of heat.
Ideally, it is best not to expose water pipes to subfreezing temperatures, by placing them only in heated spaces and keeping them out of attics, crawl spaces and vulnerable outside walls. In new construction, proper placement can be designed into the building. If you live in an older home, you may be more at risk.

Vulnerable pipes that are accessible should be fitted with insulation sleeves or wrapping (which slows the heat transfer), the more insulation the better. It is important not to leave gaps that expose the pipe to cold air. Hardware stores, like Cataldo’s, carry the necessary materials, usually in foam rubber or fiberglass sleeves. 

Cracks and holes in outside walls and foundations near water pipes should be sealed with caulking to keep cold wind away from the pipes. Kitchen and bathroom cabinets can keep warm inside air from reaching pipes under sinks and in adjacent outside walls. It's a good idea to keep cabinet doors open during cold spells to let the warm air circulate around the pipes.

Electric heating tapes and cables are available to run along pipes to keep the water from freezing. These must be used with extreme caution; follow the manufacturer's instructions carefully to avoid the risk of fire, and check to make sure the product conforms to UL 2049. Tapes and cables with a built-in thermostat will turn heat on when needed. Tapes without a thermostat have to be plugged in each time heat is needed, and may be forgotten.

Letting the Water Run
Letting a faucet drip during extreme cold weather can prevent a pipe from bursting. It's not that a small flow of water prevents freezing; this helps, but water can freeze even with a slow flow. Rather, opening a faucet will provide relief from the excessive pressure that builds between the faucet and the ice blockage when freezing occurs. If there is no excessive water pressure, there is no burst pipe, even if the water inside the pipe freezes.

A dripping faucet wastes some water, so only pipes vulnerable to freezing (ones that run through an unheated or unprotected space) should be left with the water flowing. The drip can be very slight. Even the slowest drip at normal pressure will provide pressure relief when needed. Where both hot and cold lines serve a spigot, make sure each one contributes to the drip, since both are subjected to freezing. If the dripping stops, leave the faucet(s) open, since a pipe may have frozen and will still need pressure relief.

Remove the Hose!
Remove any hoses you have attached to your outdoor faucets and then go in the house and turn off the water to the outside faucet (also called a sill cock or hose bibb). It is critical to remove any hoses attached to the outside faucet. An attached garden hose is sure recipe for frozen pipe damage in extreme cold.
The sill cock only turns water on and off outside. There is (or should be) a water shut off valve inside the house for the outside faucet. You may have to do some investigating in your home following water supply lines to try and find the shut off valve. They are usually located near the outside faucet.

If You Suspect a Frozen Pipe
If you open a faucet and no water comes out, don't take any chances. Call a plumber. If a water pipe bursts, turn off the water at the main shut-off valve (usually at the water meter or where the main line enters the house); leave the faucet(s) open until repairs are completed. Don't try to thaw a frozen pipe with an open flame; as this will damage the pipe and may even start a building fire. You might be able to thaw a pipe with a hand-held hair dryer. Slowly apply heat, starting close to the faucet end of the pipe, with the faucet open. Work toward the coldest section. Don't use electrical appliances while standing in water; you could get electrocuted.

Summary of Tips
• Leave the faucet drip slightly as a trickle. The open faucet will help alleviate pressure build-up from a freezing, and expanding, pipe.
• Open kitchen base cabinets and let room air circulate.
• Open kitchen base cabinets and place a small portable heater near or in it to heat the pipes (please follow the manufacturer’s instructions to prevent fire risk).
• Wrap the problem pipe with electrical heat tape (again, please follow the manufacturer’s instructions to prevent fire risk).
• Insulate the problem pipes with foam insulation wrap, especially those that run through unheated spaces.
• Temper unheated crawlspaces or other areas through which pipes may pass by placing a heater in the crawlspace, or simply allowing warm air to circulate from adjacent heated spaces. You just need to elevate the temperature in these areas to modestly above freezing, about 40°F.

Sources:The Weather Channel, Preventing Frozen Pipes
About.com Home Repair, Preventing and Thawing a Frozen Water Pipe