What Causes Building Drain Pipes to Freeze?
A building main drain or other building drain pipe is exposed to freezing temperatures outdoors A building drain is routed through an un-heated crawl space or basement, or an attic or attic knee-wall that is unheated indoors A plumbing fixture drain trap extends down into an un-heated crawl space or basement or is in the path of a cold draft even if the crawl space or basement is heated. A toilet is running or a faucet dribbles continuously into the drain system A water softener or other water treatment equipment is left on and running improperly, perhaps sending a continuing stream of water into the drain system A roof gutter drains into the sewer piping (bad), perhaps through a drain line that enters the building (still worse) en route to the sewer connection; clogged gutters that dribble water slowly into the drain system increases the freeze risk.
