When is it Cold Enough Pipes to Freeze?

We have reached pipe freezing temperatures several times this winter. We will reach those temperatures again in the coming days.Yes, it definitely gets cold enough for pipes to freeze in Indiana!

Since plumbing pipes typically run inside the building envelope in colder climates, it usually takes colder outdoor temperatures to freeze. In more moderate regions, the “temperature alert threshold” is 20 degrees Fahrenheit, in contrast to about zero degrees Fahrenheit in the cooler regions.

Temperature isn’t the only factor, however. Wind chill – the perceived temperature that results from the combination of temperature and moving air or wind speed – can accelerate freezing water or penetrate deeper into the home than air that is frigid but still. The pipe location also plays a role: A pipe running through the ceiling of an uninsulated basement, for example, would require colder temperatures to freeze completely than a pipe running along an outside wall in the same basement.

Why do 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 are usually safe when they are adequately protected along their entire length by placement within a building’s insulation, insulation on the pipe itself, or heating.

How Can I Prevent this from Happening?

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.