How a frost-free sillcock fails

A frost-free sillcock is designed with its shutoff valve well inside the heated house, connected to the faucet outside by a long tube. It works only if the tube can drain.

  1. A hose stays connected

    With a hose attached, water cannot drain out of the tube after the faucet is closed.

  2. The cold arrives

    The trapped water in the section passing through the cold exterior wall freezes and expands.

  3. The tube splits

    The split is inside the wall or basement ceiling, behind the valve seat. Nothing looks wrong from outside.

  4. Spring comes

    Someone opens the outdoor faucet to water the garden. Water now flows out of the split inside the house, sometimes into a finished basement ceiling or wall.

  5. The leak runs unnoticed

    Because the faucet outside seems to work, the leak can run for a long time before anyone looks inside.

Why this keeps happening

Warm spells in a Denver winter tempt people to wash a car or water trees, and the hose goes back on the spigot. The next cold front arrives before anyone takes it off. Older homes may have standard hose bibs with no frost-free design, which need an interior shutoff valve closed and the outside faucet drained before winter.

Irrigation systems can fail the same way. Backflow preventers and supply pipes that were not blown out in fall can split, and some of that piping runs through the basement before it goes outside.

Spring test for outdoor faucets

If you find a problem

  • IfThe leak is visible and has just startedThenClose the faucet and any interior valve for that line, then have a plumber replace the sillcock.
  • IfThe basement ceiling below is stained or softThenWater may have run for a while. Have moisture readings taken before the ceiling is patched.
  • IfThere is a musty smell near the faucet wallThenMention it to whoever inspects. Long-running leaks can lead to mold behind finished surfaces.
  • IfYour irrigation backflow preventer is crackedThenClose its supply valve and call an irrigation or plumbing professional.

General information for Denver, not a quote or professional advice. In an emergency, call 911.