Where the water shows up tells you the cause. A drip from the spout means a worn rubber washer or seat. A leak at the handle means worn packing, fixed by tightening the nut a quarter-turn. Water only when a hose is on, or inside the wall, often means a frost-split frost-free stem.
A drip from the spout means a worn washer or seat
If your hose bib keeps dripping from the opening even after you shut the handle all the way, the part that seals the water off has failed. On a standard compression faucet, a small rubber washer on the end of the stem presses against a metal valve seat to stop flow. That washer is the part that wears out first.
Rubber gets hard and cracks with age, and in Phoenix the Arizona sun speeds that up. A bib mounted on a sunny south or west wall takes years of heat and ultraviolet light that bake the rubber. Once the washer flattens or splits, it can no longer seal, so water sneaks past and drips from the spout.
Replacing the washer is a common do-it-yourself repair. Shut off the water to that line, unscrew the packing nut, pull out the stem, and swap the worn washer for one that matches in size and shape. If the brass seat under the washer is pitted or scratched, the new washer will fail fast too, because it cannot seal against a rough surface. A pitted seat can sometimes be reground smooth with a seat-dressing tool, or replaced outright if it threads out of the faucet body.
This kind of slow drip wastes more water than it looks. The EPA reports that a faucet leaking at one drip per second wastes more than 3,000 gallons a year. The agency puts it plainly in its guidance: "The amount of water leaked from U.S. homes could exceed more than 1 trillion gallons per year." A 50-cent washer stops that.
A leak at the handle means worn or loose packing
If water seeps out around the handle or stem only when the faucet is turned on, and stops when you close it, the problem is the packing, not the washer. Packing is the seal that wraps the stem where it passes through the body of the faucet. It keeps water from escaping along the moving stem.
The first thing to try is tightening the packing nut, the hex nut just behind the handle. Turn it clockwise a quarter-turn at a time with a wrench, then test the faucet. Often a quarter or half turn is enough to stop the seep. Do not crank it down hard, because that makes the handle stiff and can crack the nut.
If tightening does not stop it, the packing itself is worn and needs replacing. With the water off, remove the handle and packing nut, then replace the old packing washer or graphite packing string with a new one sized to the stem. This is a short repair once the water is off and the parts are out.
Water only with a hose, or inside the wall, means a frost-split stem
A frost-free (also called frost-proof) hose bib is built differently from a standard one. Its valve seat sits inside the heated wall, not at the outside spout, and the body is pitched slightly down toward the outside so the pipe drains itself after each use. That design keeps standing water out of the part exposed to cold.
The trap is a hose left attached. If a hose stays connected over a freeze, water cannot drain out of the long stem, so it freezes and splits the internal pipe. The crack hides inside the wall. You see nothing wrong until you open the faucet, and then water sprays from the break behind the wall. A telltale sign is a faucet that leaks only when a hose is attached or while it is running, then floods drywall, insulation, or a cabinet inside the house. A frost-split frost-free bib is replaced, not patched.
Phoenix winters are mild, but freezes do happen. The Department of Energy notes that "southern states generally start having issues with frozen pipes when the temperature reaches about 20 degrees Fahrenheit." Outdoor hose bibs, especially on a north wall, are among the most exposed pipes in any home. Our page on whether pipes can freeze in Phoenix covers the local risk in more detail.
A missing or failed vacuum breaker can also drip
Many hose bibs have a small dome or cap on top called a vacuum breaker, or anti-siphon device. It is a one-way air valve required by plumbing code to stop dirty water from being siphoned backward into your drinking water if pressure in the house drops while a hose sits in a pool, bucket, or sprayer of chemicals.
When the rubber seal inside that vacuum breaker wears out, it can drip or spit water from the top of the faucet while the water is running. People often mistake this for a handle leak. The fix is usually a cheap replacement vacuum breaker cap or its internal kit, sized to the faucet.
This device is not optional. The International Plumbing Code requires backflow protection on hose connections to keep contaminated water out of the potable supply. If your bib has no vacuum breaker at all, adding one is both a code matter and a health one. Our page on the hose bib vacuum breaker explains how the device works and when to replace it.
When to repair, when to replace, and how to prevent freeze damage
A standard hose bib is worth a do-it-yourself repair when the only problem is a worn washer, a worn seat, or worn packing. Those parts are cheap and the fix is straightforward once the water is shut off. Replace the whole faucet instead when the body is cracked, the threads are stripped, a frost-free stem has split inside the wall, or the bib is old enough that parts no longer match. Replacement is also the right call if you are upgrading a plain bib to a frost-free model with a built-in vacuum breaker.
Freeze prevention is simple and matters even in Phoenix. The most important step is to disconnect garden hoses before a cold night so frost-free bibs can drain and standard bibs do not trap water. The Red Cross advises that pipes can freeze when temperatures drop below 20 degrees Fahrenheit, and that exposed pipes should be protected. An inexpensive insulated faucet cover that slips over the bib adds a layer of protection on the coldest nights.
If a leak is inside the wall, the water will not stop, or you find a frost-split bib spraying behind the drywall, that is a job for a plumber before water damage spreads. HQ Plumbing & Air serves metro Phoenix 24/7 at (602) 675-1555 and can replace a failed hose bib, add a code-required vacuum breaker, or track down a hidden leak.