How to Install a Frost-Proof Outdoor Faucet

This inexpensive faucet can save thousands in water damage—and prevent water contamination

Frost-proof, anti-siphon sill cock faucets prevent winter water-line freeze-ups and stop unsanitary water from contaminating the water system. Here's how to install one in your house.

By the DIY experts of The Family Handyman Magazine


One day




$20 - $100

Step 1: Overview

In recent years, outdoor faucets (sill cocks) have undergone two great improvements.

First, a frost-proof sill cock (Figure A) puts the faucet's flow valve well within the heated walls of your home. That means if a sudden freeze occurs or you forget to shut down and drain the faucet's water line for the winter, your chances of having a pipe burst drop dramatically.

Second, an anti-siphon device (or vacuum breaker), now required by all building codes, is built into some new sill cocks (or can be added on to existing ones; Photo 8). It prevents unsanitary water from being pulled back through a garden hose and contaminating your water system.

We'll show you how to install freeze-proof sill cocks, anti-siphon valves and shutoff valves that will safeguard your home. The work will include connecting new fittings or soldering (also called “sweating”) copper joints.

Note: Our home has a galvanized piping system. The parts and installation techniques shown in the step-by-step photos are the same for copper plumbing. If you have a CPVC plastic system, however, the parts will look similar to those shown in Figure B.

Figure A: Frost-Proof, Anti-Siphon Sill Cock

The frost-proof feature works by shutting off water flow back at the stem bottom (inside a heated space). The anti-siphon feature is built into the spout. Install the sill cock through a wall with a slight downward pitch to allow any remaining water to drain out through the spout.

Cutaway of outdoor faucet.

Step 2: Call first for local plumbing rules

When you upgrade a sill cock, call your plumbing inspector to check on local requirements. (You may need a permit, too.) Although plumbing codes and enforcement vary around the country, generally they require:

  • Three-quarter inch (minimum) inside diameter supply pipes to each sill cock. Some local codes only require 1/2-in. pipe and a 1/2-in. sill cock.
  • Either an approved vacuum breaker that permanently attaches to standard sill cocks (Photo 8) or a sill cock with the feature built in (Photo 4) to prevent siphoning.
  • A shutoff valve, also called a “stop” valve, to serve each sill cock. Our code required us to install a shutoff with a built-in drain known as a “stop and waste” valve (Figure B).
  • If you have galvanized steel pipe and must make a transition to copper, install a special dielectric fitting (Photo 5) to prevent corrosion.

Freeze-Proof Strategy for Homes Built on a Slab

If your house is built on a concrete slab, a frost-proof sill cock won't work in most cases. Instead, connect a standard sill cock that's fitted with a vacuum breaker. If freezing is a concern, install a “stop and waste” valve on the pipe as close to the sill cock as possible (yet inside a heated area).

Build in an access panel so you can readily open and close the valve. In the winter, to avoid having your sill cock and pipes freeze, close the shutoff valve, uncap its drain to allow air to enter, and open the sill cock to let any water run out. Don't change these fixture settings until warmer weather permits using the sill cock again.

Step 3: Make a sketch and a parts list

Measure your existing plumbing (Photo 1), then sketch the new plumbing layout (see photo series) to use for a materials list. Draw where each pipe and fitting goes; indicate whether a part has threaded, sweat or solvent-welded joints; and label its size and description (for example, 3/4-in. copper female adapter).

If you have galvanized pipe, we recommend you unscrew the pipe back at the first coupling or fitting (Photos 1 – 3). Then insert a dielectric fitting (Photo 5) and convert to copper pipe and fittings all the way back through to the sill cock.

Frost-proof, anti-siphon sill cocks are available in 1/2-in. and 3/4-in. inside diameters, and 8-in., 10-in. and 12-in. lengths (Photo 4). Choose the diameter required by your local code and a length that will accommodate the thickness of your outside wall plus give you some working room inside to attach pipe and fittings.

We also installed a 3/4-in. “full-port” (for unobstructed water flow) ball valve with drain. There's no neoprene washer to wear out, and the easy-to-turn handle shows whether the valve is open or closed (Photo 6).

If you can't find these parts in your home center or hardware store, buy them from plumbing specialty stores (see the Yellow Pages under “Plumbing Parts, Fixtures and Supplies—Retail” or search online).

Step 4: Putting it all together

Turn off the water at the main valve where your water service enters your house, drain the system, and remove the old sill cock and pipe (Photos 2 and 3). Screw on the new sill cock (Photo 4), then reassemble the rest inside (Photos 5 – 7). Start from the old pipe end and work toward the new sill cock. It's easier to solder copper fittings to copper pipe and then screw them into hard-to-sweat parts like the ball valve and sill cock. Solder on the 3/4-in. coupling (Photo 7) last. Loosen the pipe hangers along the pipe system to allow maximum movement to fit this last connection.

Install an Anti-siphon Valve on an Existing Sill Cock

Depending on how your sill cock is currently plumbed, you may find that purchasing and installing an anti-siphon valve (also called a vacuum breaker) is all you need. Don't apply any pipe tape or compound on the sill cock spout threads. To prevent accidental removal or tampering by vandals, all plumbing codes require that vacuum breakers be permanently installed. The breaker you buy will have either a setscrew (with a break-off head) that grips the spout threads or a feature to make it hard to unscrew the breaker once it's installed.

Photo 8: Anti-siphon valve screwed to standard
sill cock.

Step 5: More installation tips

For the best results:

  • To install freeze-proof faucets through brick or concrete foundations, it may be necessary to enlarge the existing hole using a drill with a masonry hole saw. When drilling the larger hole, control drill wobble or “kick-out” by gripping the drill with two hands, keeping the hole saw centered on the old hole and running the drill at a lower speed when the saw first enters the hole.
  • Apply pipe compound or pipe tape to the male pipe threads everywhere that threaded pipe and fittings join.
  • Install new pipe level with the existing piping when they're inside a heated space. Install pipes on a downward slope if they drain toward an open sill cock once they leave the heated space.
  • Space pipe hangers every 3 ft. to support the pipe. Use copper or plastic hangers on copper pipe.
  • After replumbing the sill cock, turn the water on for at least two minutes to flush out impurities.
  • Uncouple your garden hose from the sill cock before winter. If hoses remain attached, frostproof sill cocks (whether open or closed) may freeze because water can't completely drain out of them.

Figure B: CPVS Option

If you have a CPVC supply system, omit the dielectric fitting, buy a plastic shutoff valve (with drain) and solvent-weld the pipe and fittings together. Position the valve so that its water flow direction arrow points toward the outside wall.

Figure B: CPVC supply system

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Adjustable wrench
  • Corded drill
  • Pipe wrench
  • Tube cutter


Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Pipe tape
  • Lead-free solder
  • Flux
  • Copper pipe
  • Copper fittings
  • Anti-siphon sill cock
  • Dielectric fitting (optional)
  • Shutoff
  • Silicone caulk
  • Pipe hangers

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