Repair a Leaking Frost-Proof Sillcock Faucet

Freeze proof faucet with blue knob turned and dripping water

The Spruce / Kevin Norris

A frost-proof sillcock faucet (hose spigot) is an excellent choice in climates with freezing winter temperatures, since the faucet's design prevents water from remaining inside the faucet near the exterior wall, where it can freeze and split the faucet body. The parts of a frost-proof faucet can, however, wear out and require repair or replacement.

The Design of Frost-Proof Faucets

Frost-proof faucets are designed so that the valve mechanism that seals off the water flow is located a full six, eight, or 12 inches inside the house (frost-proof wall hydrants are made in set sizes), away from the exposed exterior portion of the faucet. In older types of faucets, a long valve stem operates a rubber washer that compresses down against a valve seat located well inside the house where it remains too warm to freeze.

The faucet is designed so that any standing water inside the pipe drains out whenever the faucet is shut off. With no water in the pipe, it cannot freeze, expand, and rupture the faucet. Newer designs also have a long valve stem and self-draining feature, but rather than a rubber compression washer, they use a valve cartridge, similar to what is now used in virtually all indoor sink faucets.

Newer frost-proof sillcocks also integrate a vacuum breaker mechanism that prevents siphoning. This is now a code requirement, but older frost-proof faucets may not have this feature.

Like any faucet, a variety of routine problems can cause a frost-proof faucet to leak.

Leaks Around the Handle Stem

On older faucets that operate with compression washers, there is packing cord wrapped around the handle stem, just beneath the handle's mounting nut. If you see seeping around the threads of the handle mounting nut, this is the likely problem.

  1. Shut off the water to the faucet, either at an indoor shutoff valve or by turning off water to the entire house.
  2. Remove the handle on the spigot. Usually, this is secured with a single screw that holds the handle to the end of the valve stem.
  3. Unscrew the packing nut from around the faucet.
  4. Remove the old packing cord, and wrap several layers of new packing cord (also called graphite packing) around the end of the stem. Faucet rebuilt kits often include this packing cord.
  5. Reassemble the packing nut and reattach the handle.
Shutting off water with valve lever turned

The Spruce / Kevin Norris

Faucet spigot unscrewed with screwdriver to remove handle

The Spruce / Kevin Norris

Packing nut unscrewed unscrewed from faucet with wrench

The Spruce / Kevin Norris

New packing cord wrapped around end of faucet stem

The Spruce / Kevin Norris

Packing nut reassembled to reattach a handle

The Spruce / Kevin Norris

Leaking From Anti-Syphon Fitting

Another place a frost-proof faucet can leak is from the anti-siphon portion of the valve if the faucet has one. This component can go bad with use, and to repair it you will most likely need a new anti-siphon rebuild kit that is brand-specific to your faucet. Rebuild kits can be ordered online or purchased from a hardware store or plumbing supply house.

Because there are many brands of faucets, it is a good idea to call ahead to see if they carry rebuild kits for your brand. Be sure to shut off the water to make the repair.

It is sometimes easier, and may even be more cost-effective, to replace the entire faucet if you have difficulty finding replacement parts (which often aren't stocked in consumer-facing stores) for a frost-proof hose spigot. Replacing an entire sillcock or frost-proof hydrant is not a beginner project and is best left to professionals.

Worn-out Stem Washer or Cartridge

As with indoor faucets, by far the most common reason for leaking is a worn-out stem washer or cartridge. The symptom of this kind of leak is when closing the handle fails to stop the flow of water, which usually continues to drip or flow in a slow trickle.

With older faucets that use a compression washer at the end of the long valve stem, the repair involves getting at the washer at the end of the stem to replace it.

  1. Shut off the water to the faucet, either at an indoor shutoff valve or by turning off water to the entire house.
  2. Remove the handle from the spigot by removing the handle screw.
  3. Unscrew the faucet mounting nut, and extract the entire stem from the faucet body.
  4. Examine the washer and/or O-rings at the end of the faucet stem and replace them. The washer at the tip of the stem is usually secured by a brass screw.
  5. Reassemble the faucet, turn on the water, and test to make sure it no longer leaks.

New faucets may use a cartridge mechanism located at the end of the valve stem. For these, disassemble the faucet, in the same manner, replace the cartridge with an exact duplicate, and reassemble the faucet.

Water shut off through valve lever

The Spruce / Kevin Norris

Faucet handle unscrewed with screwdriver

The Spruce / Kevin Norris

Faucet mounting nut unscrewed to extract stem

The Spruce / Kevin Norris

Washer secured with brass screw on end of faucet stem

The Spruce / Kevin Norris

Faucet reassembled and turned on for testing water flow

The Spruce / Kevin Norris

The Flaw in the Valve Body

A frost-proof faucet can also have a hidden leak in the valve body. The symptom of this type of leak is reduced water pressure coming from the faucet.

First, check to make sure that water pressure in other fixtures is normal, and that only the frost-proof spigot is affected. If the frost-proof faucet is the only one affected, then it is likely that there is a hidden leak somewhere in the faucet body.

This may have happened because a small amount of water did not siphon out of the faucet; when it froze, a small split in the brass body was created. When this happens, each time the faucet opens, water may leak invisibly under the house or inside a wall. The solution to this problem is to replace the frost-proof faucet.