That musty smell you can't quite place
You've probably noticed it near the kitchen or a bathroom wall. Not water on the floor, nothing dramatic, just a faint mustiness that shows up when the air conditioning kicks on, or a slightly cooler patch on the drywall when you press your hand against it. Maybe the electric bill crept up a little and you can't say why. That's usually the first sign of a leak that never makes it to the floor, one that's been feeding a wall cavity or a slab for weeks or months instead.
These leaks are common in Nixa because of what our houses are built on and when they were built. A lot of homes here sit on slab foundations, especially the ranch-style houses and split-levels built from the seventies through the nineties around Christian County. Plumbing runs under that slab or through interior walls, and when a supply line or a joint starts weeping, the water doesn't pool where you can see it. It travels through soil or concrete pores and shows up as a damp smell long before it shows up as a stain.
What our clay soil and weather do to pipes
Southwest Missouri sits on a lot of clay-heavy soil, and that soil moves. It swells when it's wet and shrinks when it dries out, and Nixa gets both extremes in the same year, soggy springs followed by stretches of summer drought that crack the ground. That movement puts slow, repeated stress on pipes running under a slab or through a foundation wall. A joint that was fine for fifteen years can start to seep once the ground around it has shifted a few dozen times.
Winter adds its own version of the same problem. We don't get the brutal deep freezes of the upper Midwest, but we do get enough hard freezes, followed by quick thaws, that pipes in unconditioned crawlspaces or exterior walls take a beating. A pipe doesn't have to burst outright to start a slow leak. Sometimes a freeze just cracks a fitting enough to let it drip for months without anyone noticing.
More on this from Reading List The Quiet Leaks That Never Reach The Floor.
What you can actually check yourself
Start with your water meter. Turn off every faucet and appliance in the house, note the reading, and check it again in an hour without using any water. If it's moved, something is leaking somewhere, even if you can't see it. This is the single most reliable homeowner test and it costs nothing.
Walk your baseboards and the bottom of your walls, especially in bathrooms, the kitchen, and any room built over a slab. Look for slight discoloration, a baseboard that's started to bow or separate from the wall, or paint that's gone slightly glossy or bubbled. Feel the flooring near those walls with bare feet. Tile or laminate that feels cooler or slightly soft in one spot compared to the rest of the room is worth paying attention to.
If you have a crawlspace, get a flashlight down there once or twice a year, particularly after a hard freeze or a wet spring. Look at the undersides of supply lines and drain joints for mineral buildup, which shows where water has been dripping and evaporating, and for the kind of dark, wet soil staining that lingers long after the water itself is gone.
Where this stops being a DIY job
If your meter test shows a leak and you can't find visible water anywhere, that's the point to call a plumber rather than keep guessing. A slab leak or a wall leak needs someone with a listening device or thermal imaging to locate it without tearing out flooring or drywall on a hunch. Cutting into a slab in the wrong spot is expensive and it's easy to do when you're working blind.
The same goes for any leak near electrical outlets or panels, or one that's been running long enough that you can see or smell mold. At that point you're not just dealing with plumbing, you're dealing with material that needs to be dried out or replaced properly, and that's a bigger job than most homeowners want to take on solo.
Why waiting costs more than the fix usually does
A slow leak that never reaches the floor still runs up your water bill month after month, and it keeps feeding mold and wood rot the whole time it's hidden. The actual repair, once a plumber finds the source, is often a fairly small job, a section of pipe or a joint replaced. What gets expensive is the drywall, flooring, or subfloor damage that builds up while the leak goes unnoticed. Catching it early, with a meter check and a bit of attention to your walls and floors each season, is usually the difference between a modest repair and a much bigger one.