What is a frost free hydrant?

A common maintenance tip we hear every autumn is to remove your garden hose from the outside faucet.  But what if you have a “frost free” hydrant?

A frost free hydrant has a long stem behind the handle extending back between 8″-12″ with a set of washers at the end.  When you turn the hydrant on, it allows water to flow out of the hydrant.  When it is shut off, the water is stopped at the back of the faucet, 8″-12″ inside the house.   This is the reason that the water will continue to flow out of the hydrant for a little bit after it is turned off; it is draining out of the tube between the shut-off point inside the house, and the spout outside.  Since the water drains out of the faucet when it is shut off, the faucet is called frost free.  When it is working properly, all the water to this hydrant is 8″-12″ away from the exterior of the house.

When a hose is left on a frost free hydrant, it traps the water in the faucet.  If the trapped water is exposed to freezing temperatures, the expansion of the freezing water will cause the hydrant to burst.  Most times these leaks are not discovered until spring when you turn the hydrant on for the first time.  Usually, the hydrant only leaks when it is turned on, since the split is usually in the 8″-12″ tube.

So the answer is yes, even a frost free hydrant needs to have the hose removed before freezing temperatures arrive in autumn.

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One Response to What is a frost free hydrant?

  1. Pingback: Fall Plumbing Checklist | westjeffersonplumbingheating

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