When liquid water freezes solid, it increases in volume about 9%. As the remaining liquid water inside a pipe is relatively incompressible, this increase in volume easily breaks irrigation pipes, from flexible poly pipe to solid brass.  Anytime the air temperature drops below freezing (32 degrees F) for several hours, exposed pipes containing water are at risk to freeze and break, especially above ground pipes such as hose bib risers and back-flow prevention valves.

DUG and agency partners begin turning off water at gardens in early to mid October. The average date of first freeze for Denver is October 7th, therefore DUG staff closely monitor weather forecasts starting in October to evaluate the latest date to turn off water while minimizing the risk of freeze breaks in water systems. Once the water is turned off, the irrigation lines are drained and/or blown out with compressed air to remove all water, thereby eliminating the risk of costly, wasteful and time consuming freeze breaks.

Last updated on September 1, 2011 by Denver Urban Gardens