Can Water Heater Drains Freeze?

Drains Can Freeze

• Water heater drains exist only for servicing purposes and to vent water that would otherwise flood the building during an emergency. They should not, under normal operation, contain water. However, situations can occur where a small volume of water drips unnoticed from an otherwise functioning water heater, and this water can be directed to the outside of the building through the drain line. If this should occur and any part of the drain line is exposed to sub-freezing temperatures, the trickle could incrementally freeze until it becomes a solid ice plug that then backs up water or ice into the building. Drains, therefore, can freeze.

Danger Point

• Perhaps surprisingly, 32 degrees Fahrenheit is not the point at which appliances and pipes containing water become vulnerable. The specialists at the U.S. Department of Energy note that water-bearing systems “Need protection from freezing in climates where temperatures fall below 42 degrees F.”

Winterizing

• As the experts at Handyman Fix Home Repair observe, “If your house will be occupied during the winter, then you only need to ensure that exposed piping gets drained and protected.” In unheated buildings all water-bearing appliances, including water heaters, must be entirely winterized -- emptied with an air compressor, or drained and filled with an antifreeze solution -- through the cold season. As noted above, a water heater inside a heated building may still have a drain line that passes outside into an unprotected environment. That being the case, that drain line must be separately protected.

Exterior Insulation

• Wrapping an exterior pipe with insulation will not be sufficient to ensure water passing slowly through it does not freeze. A stop tap installed inside the building at the head of the drain line could defeat the object of having the drain; it could artificially prevent water that should be vented from escaping. Electrical heating tape that is kept warm by a transformer plugged into the mains is the ideal solution; such tape only uses a tiny trickle-charge of electricity, but keeps the surface of the pipe above the temperature at which the water could freeze.