Valve Leak Repair
Updated February 24, 2026
A dripping valve usually isn't a big deal -- until it is. A slow drip from a shut-off valve under the sink seems minor, but it causes water damage, mold, and eventually a valve that fails completely when you need it. Most valve leaks are fixable in place without shutting off the main. The fix depends on where the leak is coming from.
Overview
A dripping valve usually isn't a big deal -- until it is. A slow drip from a shut-off valve under the sink seems minor, but it causes water damage, mold, and eventually a valve that fails completely when you need it. Most valve leaks are fixable in place without shutting off the main. The fix depends on where the leak is coming from.
What to Know
Packing Nut Leaks
- The most common valve leak.
- The packing nut is the nut right behind the handle.
- It compresses packing material around the valve stem to create a seal.
- When this material wears or dries out, water seeps past the stem.
- The fix is usually tightening the packing nut a quarter turn.
- If that doesn't work, repack the valve with new packing material or a new packing washer.
Handle or Stem Leaks
- If water leaks from around the handle when the valve is operated, the stem O-ring or packing is worn.
- On ball valves, this is less common because the stem seal is more robust.
- On gate and globe valves, stem leaks are frequent after years of use.
- Replacement O-rings and packing washers are available at any hardware store.
Body or Connection Leaks
- Leaks from the valve body itself (cracks or pinholes) or from the threaded connections where the valve meets the pipe.
- Body leaks mean the valve needs replacement -- you can't patch a cracked brass valve body reliably.
- Connection leaks may just need the fitting tightened or new thread seal tape applied.
Seat Leaks (Through-Flow)
- The valve is closed but water still passes through.
- This means the seat inside the valve is worn or damaged.
- Gate valves are notorious for this -- the gate corrodes and no longer seats flush against the body.
- Ball valves rarely have this issue.
- A valve that won't fully shut off needs replacement.
Safety Warnings
- Overtightening the packing nut until the handle won't turn. This doesn't fix the leak and makes the valve unusable.
- Ignoring a slow drip because it seems minor. Water damage accumulates silently.
Step by Step
- Identify the leak source
Dry the valve completely with a towel. Watch carefully to see exactly where water appears. Packing nut leaks show up around the stem when the valve is operated. Connection leaks appear at the pipe joints. Seat leaks show as water flowing downstream when the valve is fully closed.
- Tighten the packing nut
Use an adjustable wrench to turn the packing nut clockwise -- just a quarter turn. Test. If it still drips, another quarter turn. Don't overtighten -- the handle should still turn smoothly. If tightening makes the handle very stiff but it still leaks, the packing needs replacement.
- Repack the valve
Shut off water upstream. Remove the packing nut. Pull out the old packing material. Wrap new graphite packing rope (or a new rubber packing washer) around the stem. Reassemble the packing nut and tighten. Turn water back on and check.
- Fix connection leaks
For threaded connections: shut off water upstream, unthread the connection, clean the threads, apply new PTFE tape (3-4 wraps clockwise), and reconnect. For compression fittings: tighten the compression nut a quarter turn. If it still leaks, replace the ferrule.
Pro Tips
- Keep spare packing washers and PTFE tape under the sink. These two items fix the majority of valve leaks.
- When tightening packing nuts, use two wrenches -- one on the packing nut and one to hold the valve body. This prevents stress on the pipe connections.
- If you're replacing a gate valve, upgrade to a ball valve. The cost difference is small and ball valves are far more reliable.
- A slow drip into a bucket overnight tells you the leak rate. If it's more than a cup per hour, fix it now.
Mistakes to Avoid
- Overtightening the packing nut until the handle won't turn. This doesn't fix the leak and makes the valve unusable.
- Ignoring a slow drip because it seems minor. Water damage accumulates silently.
- Applying pipe dope or tape to compression fittings. Compression fittings seal metal-to-metal -- sealant can actually prevent a proper seal.
- Trying to repair a cracked valve body. Replace it. A cracked body will fail completely under pressure.
When to Call a Pro
If the valve is in an inaccessible location, if the pipe connections are corroded and won't unthread, or if you need to shut off the main to work on the valve and the main shutoff is also seized, call a plumber. Valve replacements in difficult locations typically cost $100-$250.
Bottom Line
Most valve leaks are packing nut issues -- a quarter turn with a wrench fixes them. Connection leaks need new tape or tightening. Body cracks and seat failures mean replacement. Fix small leaks now before they become big problems.
Frequently Asked Questions
What are expert tips for valve leak repair?
Keep spare packing washers and PTFE tape under the sink. These two items fix the majority of valve leaks. When tightening packing nuts, use two wrenches -- one on the packing nut and one to hold the valve body. This prevents stress on the pipe connections. If you're replacing a gate valve, upgrade to a ball valve. The cost difference is small and ball valves are far more reliable. A slow drip into a bucket overnight tells you the leak rate. If it's more than a cup per hour, fix it now.
What mistakes should I avoid with valve leak repair?
Overtightening the packing nut until the handle won't turn. This doesn't fix the leak and makes the valve unusable. Ignoring a slow drip because it seems minor. Water damage accumulates silently. Applying pipe dope or tape to compression fittings. Compression fittings seal metal-to-metal -- sealant can actually prevent a proper seal. Trying to repair a cracked valve body. Replace it. A cracked body will fail completely under pressure.
When should I call a professional for valve leak repair?
If the valve is in an inaccessible location, if the pipe connections are corroded and won't unthread, or if you need to shut off the main to work on the valve and the main shutoff is also seized, call a plumber. Valve replacements in difficult locations typically cost $100-$250.
What is the bottom line on valve leak repair?
Most valve leaks are packing nut issues -- a quarter turn with a wrench fixes them. Connection leaks need new tape or tightening. Body cracks and seat failures mean replacement. Fix small leaks now before they become big problems.
When should I call a professional for valve leak repair?
If the valve is in an inaccessible location, if the pipe connections are corroded and won't unthread, or if you need to shut off the main to work on the valve and the main shutoff is also seized, call a plumber. Valve replacements in difficult locations typically cost $100-$250.
What's the bottom line on valve leak repair?
Most valve leaks are packing nut issues -- a quarter turn with a wrench fixes them. Connection leaks need new tape or tightening. Body cracks and seat failures mean replacement. Fix small leaks now before they become big problems.
How much does valve leak repair cost?
The typical cost range is $2-$15 DIY / $100-$250 with plumber. Actual costs depend on your location, materials, and whether you hire a professional.
How difficult is valve leak repair?
This task is rated Easy to Intermediate. It requires moderate DIY skill.