Many homes in O'Fallon have decades of plumbing behind the walls, and the cabinet under the kitchen or bathroom sink is the easiest place to see what condition it is in. You do not need special tools to start. A flashlight, a dry paper towel, and a few minutes of patience are enough for a first look.
Start with the supply lines
The supply lines carry water from the shutoff valves up to the faucet. The material tells you a lot about how old the system is and what to watch for.
- Galvanized steel is dull gray with a rough surface. It was common in older homes. Look for flaking, orange rust, or crusty buildup at the joints, since it can corrode from the inside out.
- Copper is smooth and reddish. A green or blue-green crust at a fitting often means a slow seep has been leaving deposits behind.
- Braided stainless flexible lines have a metal mesh jacket. Check where the mesh meets the fittings and look for bulging or cracking in the inner hose.
- Plastic lines are usually white, gray, or blue. Check for cracks, stiffness, or bulges near the connections.
Check the joints and valves
Most leaks start at connections rather than in the middle of a run of pipe. Dry the area, then run a paper towel along each fitting, the shutoff valve stems, and the base of the faucet. If the towel picks up moisture after you run the water, you have a slow leak that needs attention.
Hard water is common in O'Fallon, and it leaves mineral scale. A white or chalky crust around a valve or aerator is usually mineral buildup, but it can also hide a seep. Wipe the crust away, dry the fitting, and check again over the next several days. If the crust returns with moisture underneath, treat it as a leak.
Look at the drain and trap
The curved pipe under the sink is the trap, and it is often the oldest part of the drain. Older traps may be cast iron, galvanized steel, or thin plastic that has become brittle. Look for these signs:
- Bent, pitted, or rusted metal parts
- Cracks or hairline splits in plastic
- Loose slip nuts that drip when water runs
- Water staining on the cabinet floor below the trap
- A sewer odor, or a drain that empties slowly
A slow drain or a sewer smell can have causes beyond the trap, so note what you see and mention it when you call someone for help.
Check the cabinet floor and back wall
Press gently on the cabinet floor near the supply lines and the drain. Soft, dark, or swollen wood means water has been reaching it for some time. A musty smell, stains on the back panel, or dark patches on the wood call for opening the cabinet further and looking at the wall behind it.
Things that are harder to see
Some older homes in the area have lead solder on copper joints, or older service lines that are not visible from under the sink. Lead is a metal that can be tested for through a certified laboratory, and a plumber can often tell you what material is behind a wall. If your home is on a private well, a separate test for coliform and E. coli through the Missouri State Public Health Lab is a practical step. That test looks at the water source, not the pipe under the sink, so keep the two questions separate.
Decide what to do next
- If you see only mineral crust and every joint stays dry, clean the area, recheck it in about a week, and keep a short note of what you find.
- If you see an active drip, a seep, or rust at a fitting, shut off the valve under the sink and have that connection looked at soon.
- If the cabinet floor is soft, or the supply lines are galvanized, corroded, or clearly past their useful life, have a licensed plumber review the full run from the wall to the fixture.
- Keep the shutoff valves working. Turn them gently every so often so they do not seize when you need them in an emergency.
When you do call someone, describe what you saw: the pipe material, where moisture shows up, and how old the fixture or cabinet appears. That gives a clear picture before anyone opens a wall. Older plumbing in O'Fallon is often workable, and a careful look under the sink now makes the next decision much simpler.