A dripping shutoff (angle stop) under a sink or toilet seems minor—until it ruins a cabinet floor or stains a ceiling. The good news: many leaks are quick DIY fixes if you know where to look. The bad news: older Pasadena homes often have aging multi-turn valves and short copper stub-outs that complicate repairs. Below, Pershing Plumbing explains how to diagnose and fix the most common shutoff valve leaks, plus when to call in help. Throughout, our Pasadena Plumbing experts recommend safe, code-conscious steps that protect your home and budget.
Quick Answer: Try these steps in order
- Identify where the leak originates: stem/packing, compression nut, supply line connection, or valve body.
- For stem seepage: gently tighten the packing nut 1/8–1/4 turn.
- For compression joint weeps: snug the nut; if it persists, re-make the connection with a new ferrule.
- For supply-line leaks: replace the line and washers—use braided stainless.
- For corroded or stuck valves: replace with a quarter-turn ball valve (compression or push-to-connect).
- Always shut off the home’s main water before replacing a valve.
Our Pasadena Plumbing experts recommend starting with the least invasive fix and working up only as needed.
Safety and prep
- Turn off water: If the local shutoff won’t stop the flow, locate and close the main shutoff to the house.
- Relieve pressure: Open a nearby faucet to depressurize.
- Protect the area: Place a towel or pan under the valve.
- Tools: Adjustable wrench, small channel locks, screwdriver, utility knife, flashlight, Teflon paste (only for NPT threads), emery cloth/deburring tool, replacement ferrules/nuts/supply lines, and optionally a ferrule puller.
- Personal safety: Wear eye protection. Don’t overtighten—brute force can crack valves or deform soft copper.
Our Pasadena Plumbing experts recommend keeping spare braided supply lines and a couple of 3/8-in. compression ferrules in your home kit.
Step 1: Find the exact leak source
Dry everything, then wrap a tissue around one area at a time while the valve is open and pressurized:
- Stem/packing leak: Tissue gets wet around the valve handle/stem.
- Compression joint leak: Moisture forms behind the valve where it meets the wall pipe (the large hex nut).
- Supply-line leak: Water at the small nut where the line connects to the valve or at the fixture.
- Valve body leak: Corrosion or pinhole on the valve body itself; replace the valve.
Our Pasadena Plumbing experts recommend diagnosing before turning wrenches—guessing can make a simple fix harder.
Fix A: Stem/packing leaks (common on older multi-turn valves)
- Gently tighten the small packing nut behind the handle by 1/8–1/4 turn while the valve is open. Stop if resistance spikes.
- If it still seeps, close the home’s main, open a faucet to drain, then remove the handle and packing nut. Add a wrap or two of graphite/PTFE valve stem packing string around the stem, reassemble, and test.
- Persistent stem leaks or gritty operation = replace the valve.
Tip: In Pasadena’s hard water, mineral buildup accelerates packing wear. Our Pasadena Plumbing experts recommend upgrading to quarter-turn ball stops to eliminate stem-packing headaches.
Fix B: Compression joint leaks at the wall pipe
Applies when your valve attaches to a copper stub-out with a compression nut and brass ferrule.
- Try a small snug: hold the valve body with one wrench so you don’t twist the wall pipe; tighten the compression nut 1/8 turn with a second wrench.
- If it still weeps, re-make the joint:
- Shut off the main. Remove the compression nut and valve.
- Ideally, install a new nut and ferrule with the new valve. If the old ferrule is stuck, use a ferrule puller. Avoid prying against the wall or twisting the pipe inside the wall.
- Clean and deburr the copper. Slide on new nut and ferrule. Seat the valve straight and tighten until snug, then an additional 1/4–1/2 turn. Do not over-crush the ferrule.
Our Pasadena Plumbing experts recommend avoiding thread tape on compression threads—they seal at the ferrule, not the threads.
Fix C: Supply-line leaks (fastest win)
- Replace old plastic or corrugated lines with braided stainless lines.
- Toilet supply lines use 7/8-in. ballcock x 3/8-in. compression; faucets typically use 3/8-in. compression x faucet-specific connection.
- Hand-tighten, then add 1/4 turn with a wrench. Do not overtighten plastic inlet shanks on toilets and faucets.
Our Pasadena Plumbing experts recommend replacing supply lines every 5–7 years or any time you replace a valve or fixture.
Fix D: Valve body is corroded, stuck, or won’t shut off
Replace the valve. You have three common scenarios:
- Compression replacement (copper stub-out)
- Best when you already have a compression stop.
- Remove the old valve; replace the nut and ferrule with new ones.
- Install a quarter-turn ball valve angle stop or straight stop to match your layout.
- Pros: Reliable, no flame. Cons: Requires good access and a sound stub-out.
- Push-to-connect replacement (copper, PEX, or CPVC)
- Cut the old valve off squarely with a tubing cutter, leaving at least 1 inch of clean, round pipe.
- Deburr inside and outside. Mark the insertion depth; push the new stop fully seated.
- Use the proper pipe insert for PEX.
- Pros: Fast, great in tight spaces. Cons: Pipe must be clean, unscratched, and properly supported.
- Code note: Push-to-connect fittings are widely accepted for repairs, but our Pasadena Plumbing experts recommend using listed, brand-name fittings and verifying local approval.
- Sweat-soldered valve (older installs)
- If you’re experienced with soldering, you can desolder/replace. Otherwise, cut and use compression or push-to-connect to avoid open flame near walls.
- Protect combustibles; have a fire extinguisher ready.
- In plaster-and-lath or very short stub-outs, call a pro—damage risk is high.
Our Pasadena Plumbing experts recommend quarter-turn ball valves for all replacements. They’re more reliable, resist mineral buildup, and clearly indicate on/off.
Turn water back on and test
- Slowly crack the home’s main open to pressurize gradually.
- Partially open the new shutoff and check every joint with a dry tissue. Look for “sweating” that can indicate a slow seep.
- Fully open the valve and recheck after 5 minutes, then again after a few hours.
- For toilets, flush several times and inspect both ends of the supply line.
Pro tip: Place a paper towel under the valve overnight. Any drips leave a clear mark. Our Pasadena Plumbing experts recommend re-snugging compression nuts only if you see moisture—don’t chase a dry connection.
Preventive upgrades and maintenance
- Exercise valves twice a year: close and open to prevent seizing.
- Standardize on quarter-turn ball stops and braided stainless lines.
- Replace corroded escutcheons and secure loose stub-outs to prevent movement.
- Add leak pads or trays in sink cabinets for early detection.
- Hard water alert: Pasadena’s mineral content is tough on rubber parts. Our Pasadena Plumbing experts recommend whole-home conditioning or at least routine aerator and angle stop checks.
When to call Pershing Plumbing
- The valve won’t fully shut and the main is hard to operate.
- The copper stub-out is very short, spins, or wiggles in the wall.
- You see green/white crust (dezincification/corrosion) across multiple fittings.
- You have galvanized or mixed-metal transitions.
- You’re unsure whether your valve is compression, sweat, CPVC, or PEX.
- There’s any sign of wall moisture or cabinet damage—hidden leaks spread fast.
Our Pasadena Plumbing experts recommend addressing shutoff issues before a fixture replacement or remodel so you’re not caught without a working local valve during future work.
FAQ
- Do I need Teflon tape?
- Only on tapered NPT threads. Do not tape compression threads or the supply-line nut to the valve; those seal on the ferrule or washer. Our Pasadena Plumbing experts recommend a quality PTFE paste for NPT when space is tight.
- Angle stop vs. straight stop—what’s the difference?
- Angle stops turn 90 degrees (for wall stub-outs under sinks/toilets). Straight stops connect inline (often from floors).
- Can I reuse a compression ferrule and nut?
- It’s possible but not ideal. Reusing increases leak risk. We recommend new ferrules and nuts whenever you replace the valve.
- How tight is tight enough?
- Snug plus a quarter turn is a good starting point. Check for weeping. Overtightening can deform copper and cause permanent leaks.
Pershing Plumbing fixes and upgrades leaking shutoff valves every day across Pasadena. If you want a clean, code-compliant repair with durable quarter-turn stops and fresh supply lines, our Pasadena Plumbing experts recommend scheduling a quick service call. We’ll diagnose, replace, and pressure-test so your cabinets stay dry and your fixtures are easy to service.