How to Spot and Fix a Leaky Shut-Off Valve Under Your Sink (And When to

If you’ve ever opened the cabinet under your kitchen or bathroom sink and noticed water pooling or that musty, damp smell — chances are your shut-off valve is leaking. It’s a small part that causes big headaches, especially for homeowners in older homes across Van Nuys, Burbank, Santa Monica, Calabasas, and the rest of the San Fernando Valley.

In this article, we’ll show you how to spot the signs of a leaky shut-off valve, explain what might be causing the problem, walk you through common DIY solutions, and — most importantly — explain when it’s time to call in a licensed plumber from CrackerJack Plumbing Pros.

What Is a Shut-Off Valve, and Why Does It Leak?

A shut-off valve (also called an angle stop or supply valve) is the small knob or lever you turn to stop water flow to your faucet, toilet, or appliance. These valves often go untouched for years, which is part of the problem.

Over time, shut-off valves can begin to:

Drip from the handle or packing nut
Leak at the connection to the supply line or pipe
Fail internally, allowing water to flow even when turned off

Mineral buildup from LA’s hard water, corrosion from age, or poor original installation can all contribute to these slow leaks.

Signs You Have a Leaky Shut-Off Valve

Whether you’re in Glendale, Encino, or Woodland Hills — here’s what to look for:

Pooled water under the cabinet, especially after turning the valve
Mildew smell or swelling wood under the sink
Water stains or corrosion on the valve itself
Dripping sound when everything is turned off
Water running down the pipe when the valve is opened or closed

These issues can be subtle at first but lead to expensive water damage if ignored.

Can You Fix It Yourself?

Sometimes. Here are a few things you can try:

1. Tighten the Packing Nut

Use an adjustable wrench to slightly tighten the small nut just behind the valve handle. Be careful — overtightening can crack the valve.

2. Replace the Supply Line

If the leak is coming from where the supply hose connects, you may just need a new braided supply line.

3. Try Turning the Valve On and Off

Sometimes opening and closing a stuck valve can reseat the internal washer and temporarily stop a slow drip.

When DIY Isn’t Enough (And It’s Time to Call a Pro)

Here’s the thing: shut-off valves are often sweated (soldered) or compression-fit to copper pipes. Replacing them isn’t always a simple unscrew-and-swap — especially in older homes across Los Angeles where pipes can be fragile or access is tight.

You should call CrackerJack Plumbing Pros if:

The valve continues leaking after tightening
You notice corrosion or rust
The valve doesn’t fully shut off water
You’re not comfortable turning off the main water supply
You want a long-term fix done safely and cleanly

We’re fully licensed, bonded, and insured to handle all types of valve replacements — from compression and sweat-style fittings to full pipe repairs.

Why Choose CrackerJack Plumbing Pros?

We’re proud to serve homeowners across Los Angeles, including Van Nuys, Burbank, Santa Monica, Calabasas, and the surrounding San Fernando Valley. We show up on time, explain every step, and stand behind our work with honesty and professionalism.

If you’ve got a leak, we’ll fix it right — no band-aid solutions. And yes, we do offer same-day appointments for urgent plumbing issues.

Get a Professional Plumbing Inspection Today

If you’re dealing with a leak under your sink or just want peace of mind, give us a call. We’ll inspect your shut-off valves, check for other hidden leaks, and make sure everything is running smoothly.

📞 Call CrackerJack Plumbing Pros at

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