Common Under Sink Problems We Fix

P-Trap Leaks and Replacement

The P-trap is the curved section of drain pipe under the sink that holds a small amount of water to block sewer gases from coming up through the drain. P-trap leaks are one of the most frequent under-sink issues we see. They happen at the slip joint connections on either end of the trap — the slip nuts work loose over time from vibration and thermal cycling, or the rubber washers inside them harden and crack with age.

Sometimes tightening the slip nut stops the leak. When the washer has deteriorated or the trap itself is cracked or corroded, we replace the trap assembly. In older Burleson homes we often find P-traps that are a mix of different pipe sizes held together with mismatched adapters — we sort these out correctly so the connection is solid rather than just patched.

Drain Basket and Sink Strainer Leaks

The drain basket is the fitting that connects the sink bowl to the drain pipe below. It’s sealed with plumber’s putty around the top flange where it sits in the sink, and a rubber gasket and locknut underneath. When the putty dries out and cracks or the gasket deteriorates, water seeps down the outside of the drain basket rather than through it — often pooling under the sink in a way that looks like the P-trap is leaking but actually isn’t.

Replacing a drain basket requires removing the old fitting, cleaning the drain opening, reseating the new fitting with fresh putty, and securing it from below. It’s a straightforward repair that permanently stops this type of leak.

Supply Line Leaks

The braided stainless supply lines connecting the shut-off valves to the faucet are under constant water pressure. They develop leaks at the fittings on either end — either at the valve connection below or the faucet connection above. The internal rubber hose inside the braided outer layer also deteriorates over time and can fail without warning, sometimes suddenly.

Supply lines have a recommended replacement interval of about 10 years — original supply lines in a home built in the late 1990s or early 2000s are well past that. We replace supply lines as part of faucet and under-sink repair visits whenever we find ones that are aging or showing any signs of deterioration.

Shut-Off Valve Replacement

The angle stop valves under kitchen and bathroom sinks are there for one critical purpose — to shut off the water to that fixture in an emergency without turning off water to the whole house. In older Burleson homes, original shut-off valves that haven’t been turned in 20 or 30 years are frequently corroded to the point where they can’t be safely operated. Forcing a stuck angle stop can snap the stem or cause the valve body to leak.

We replace corroded or non-functioning shut-off valves as a standard part of under-sink repair visits when we find them in this condition. A functional shut-off valve under every sink is a basic safety requirement — it’s not an optional upgrade.

Garbage Disposal Mounting Flange Leaks

The garbage disposal mounts to the sink drain opening via a mounting flange assembly sealed with plumber’s putty. Over time — particularly in kitchens where the disposal experiences heavy vibration — the putty seal fails and water seeps down the outside of the flange. This leak appears to come from the top of the disposal but is actually at the sink connection above it.

Fixing this requires removing the disposal, cleaning and reseating the flange with fresh putty, and reinstalling. We check the disposal mounting assembly any time we’re working under a kitchen sink and the disposal is present.

Drain Clogs Under the Sink

Slow drains and clogs directly under the sink — in the P-trap or the short section of drain pipe between the trap and the wall — are common in kitchen sinks from grease accumulation and in bathroom sinks from hair and soap buildup. We clear these as part of under-sink repairs when a clog is contributing to the problem. For drain issues deeper in the wall or main line, see our Drains page.

Faucet Supply Connection Issues

Faucet supply lines connect to the faucet body through the sink deck above — the connections come down into the cabinet space below. These connections can loosen over time or develop slow drips that pool in the cabinet. If the leak appears to be coming from the top of the supply line where it enters the faucet, the faucet connection may need tightening or the supply line needs replacement. If the faucet itself is the source of the leak, see our Faucets page.

Why Under-Sink Leaks Cause More Damage Than They Look Like

A slow drip under the sink that gets ignored for weeks or months causes more damage than most homeowners expect. The cabinet floor — usually particle board in most Burleson-area homes — absorbs moisture and begins to swell, warp, and eventually disintegrate. The cabinet frame, the wall behind it, and the floor underneath can all be affected. Mold can develop in as little as 24 to 48 hours in a dark, moist cabinet space.

If you’ve found a leak under your sink, check the cabinet floor for soft spots, warping, or staining before we arrive and let us know what you find — the condition of the cabinet helps us understand how long the leak has been running and whether any cabinet repair is warranted alongside the plumbing fix.

Frequently Asked Questions — Under Sink Repairs

How do I find where the leak is actually coming from?

Dry everything under the sink with a towel, then run the water and watch carefully. Water that appears at the P-trap connections is a slip joint leak. Water running down the outside of the drain basket from above is a putty seal failure. Water at the bottom of the supply lines is a fitting leak. Water appearing only after using the disposal points to the flange. If you can’t isolate it, call us and we’ll find it.

Can I fix a P-trap leak myself?

Sometimes — tightening the slip nut may stop a minor drip if the washer is still in decent shape. If tightening doesn’t stop it or the washer is clearly hardened and cracked, replacing the trap is the right fix. It’s a straightforward repair but does require matching pipe sizes correctly, having the right fittings, and making sure the trap is properly sloped. If you’ve tried tightening and it’s still dripping, give us a call.

Should I replace my shut-off valves even if they’re not leaking?

If they’re original to an older home and have never been turned, yes — it’s worth replacing them proactively. A shut-off valve that fails when you desperately need to stop water flowing to a broken supply line is a far more expensive problem than replacing the valves during a routine repair visit. We replace these whenever we find them in questionable condition.

The cabinet floor under my sink is soft — do you fix that too?

We fix the plumbing. Cabinet and flooring repairs are typically handled by a separate contractor. We’ll let you know the condition of what we find when we’re in there, and we can point you toward someone for the cabinet work if needed.

Schedule Your Under Sink Repair

Don’t let a slow drip become a rotted cabinet. Most under-sink repairs are completed same day — give us a call and we’ll get it sorted.

📞 Call Dependable Plumbing at (817) 447-2654
Free estimates · Same-day service available · Serving Burleson and south DFW since 1985