Find where the water appears. Wet under the handle points to worn stem packing, a drip at a nut points to a loose or overtightened joint, a wet braid points to a failing supply line, and water from the valve body means a failed stop. Snugging the packing nut slightly is safe to try.
Where is the leak actually coming from?
Dry everything with a paper towel, then watch. Wipe it along each spot and see which one gets wet first.
- Under the handle. The stem packing is leaking. That is the seal around the stem. See why a shut-off valve leaks at the handle.
- At a nut. The compression nut where the line meets the stop outlet, or the nut at the other end of the line, is loose, cross-threaded or overtightened.
- Along the line itself. Water beading on the braid, rust or crust on the braided steel, or a drip at the crimped end means the line is failing.
- From the body of the stop. Water seeping through the brass, or from the joint where the stop meets the wall pipe, means the valve has failed.
A leak that only shows when the faucet runs may be on the drain side. See water leaking under a sink.
Why does a stop leak at the stem?
The packing around the stem wears as the handle turns, and a stop left untouched for years often starts weeping the first time someone moves it. BrassCraft sells a stem repair kit that it says "is for angle and straight style multi-turn valves." Our page on a shut-off valve leaking at the handle covers how to snug the packing nut and when to give up on it.
Why does a compression nut or supply line connection drip?
Often, the nut was tightened wrong. Too loose leaks. Too tight is just as bad.
BrassCraft's stop instructions warn: "Overtightening can cause product to crack and fail over time." For a tube joint at the stop outlet, they add: "If cocked or tilted, nut will not seat properly and could eventually develop a leak." For supply connectors with metal nuts, the same BrassCraft instructions say to "hand tighten, then wrench tighten 1/4 turn more." Fluidmaster's instructions for its toilet line say "If leak appears, tighten nut just enough to provide a leak-free joint." Fluidmaster's plastic Click Seal nut is hand tight only, with a torque rating of "15-20 in-lbs." It says "Tools are not recommended nor needed to install the Click Seal nut."
The pattern is the same across the makers. A little past hand tight, then stop. A joint that still drips after that usually has a damaged washer, a nicked thread or a crooked seat, and more force makes it worse.
Why does a braided supply line leak?
A braided line is a hose inside a steel sleeve. The hose and washers inside can still wear out. Common causes:
- Age. Washers harden and hoses weaken. Some makers print a replacement interval on the packaging or instructions, so check yours.
- Kinks and stretching. A line bent sharply or pulled tight has a weak spot.
- Overtightening. Too much force on the nut can damage the washer and threads.
- Corrosion. Rust or crust on the braid or the end fitting is a sign to replace the line.
A line that leaks is done. Our guide to replacing a toilet supply line walks through the steps, and the same approach works for a faucet line.
What can I safely try myself?
Start with the cut-off, then the gentlest fix.
- 1Know your main shut-off. If the stop won't hold, shut off water upstream at the main. See how to test your main water shut-off valve before you need it.
- 2Snug the packing nut a little. For a leak under the handle, turn the packing nut a small fraction, wait, and check. Stop when the drip stops. If the handle gets stiff, you have gone far enough.
- 3Reseat a dripping nut. For a leaking slip-joint nut on a riser tube, BrassCraft says to "turn off water supply. Back off (loosen) nut completely, realign and retighten." For a supply line with a metal nut, hand tighten and add a quarter turn.
- 4Do not keep cranking. Extra force on a nut that still drips risks cracking the part.
If the valve itself will not close, the fix is a replacement, not tightening. See why an angle stop won't shut off all the way.
When should I replace the stop or the line?
Replace the line when it leaks, shows corrosion or has a kink, or when the stop is replaced.
Replace the stop when:
- It leaks from the body or the joint at the wall.
- The packing nut has no more travel, or the leak returns soon after you snug it.
- It will not fully close, or the handle is stuck.
- You see corrosion or mineral crust on the brass.
BrassCraft's stop instructions are direct: "Do not reuse, inspect annually, replace if damaged, deterioration or corrosion is detected. Failure to do so may result in product failure and property damage." For the swap, see how to replace a toilet shut-off valve. Sink stops work the same way.
Phoenix's adopted plumbing code also expects the stop to exist and be reachable. Section 606.2 requires shutoff valves "On the fixture supply to each plumbing fixture other than bathtubs and showers in one- and two-family residential occupancies," and Section 606.3 says "Access shall be provided to all full-open valves and shutoff valves." If yours is leaking, it is not doing that job.
When is it an emergency?
Spraying water, a burst line, or a valve you cannot turn off means shutting the water off at the main right away. A slow drip can wait for a scheduled visit, but keep a container under it and check it daily.
HQ replaces angle stops and supply lines throughout the Valley. We are licensed and insured, available 24/7 for emergencies, and give free estimates with upfront pricing. See our home plumbing services.