That midnight running sound
You are lying in bed and the house is quiet, and then you hear it: a soft hiss or gurgle from the bathroom, then the rush of water refilling the tank, then nothing again for twenty minutes. It happens two or three times a night. Nobody flushed. Nobody used the toilet. It just runs on its own.
This is called a phantom flush, and it is one of the most common calls in older Nixa homes, especially the ranch-style houses off Mt. Vernon and the subdivisions built up through the 80s and 90s around Gregg Road and South Street. The toilet is not haunted. It has a slow leak between the tank and the bowl, and it is losing just enough water to trigger the fill valve every so often.
What is actually happening inside the tank
Every toilet tank has a flapper, a rubber or silicone seal at the bottom that lifts when you flush and drops back down to hold water in the tank. When that seal degrades or does not sit flat, water seeps past it into the bowl, drop by drop, all night long. Eventually the tank level drops low enough that the fill valve kicks on to top it back up. That is the sound you are hearing.
Flappers do not last forever. Five to seven years is typical, sometimes less if the water has a lot of mineral content, which is common with Nixa's well and municipal supply drawing off the Ozark aquifer system. Hard water leaves a gritty film on rubber parts, and that film keeps the flapper from forming a clean seal even when the part looks fine to the eye.
More on this from A Toilet That Refills By Itself Overnight.
What you can check yourself
Take the lid off the tank and look. If the water level sits above the overflow tube, it is running down that tube constantly and refilling for a different reason, usually a fill valve that needs adjusting or replacing. If the level looks normal but the flapper is warped, cracked, or has a chalky buildup along the edge, that is your leak.
A simple test: drop a few drops of food coloring into the tank water and do not flush. Check the bowl in twenty minutes. If the color has crept into the bowl, water is bypassing the flapper. Replacing a flapper is a job most homeowners can manage in under half an hour with a ten dollar part from a hardware store, and it solves the majority of phantom flush cases.
While you are in there, check the chain connecting the flapper to the flush handle. If it is too tight, it can hold the flapper open just a crack. Too loose, and it might not lift the flapper fully when you do flush. Either way it is an easy adjustment.
When it is not the flapper
If you replace the flapper and the toilet still refills overnight, the problem is likely the fill valve itself, or a crack in the tank or bowl that you cannot see from above. Older toilets, especially the ones original to homes built before the mid-90s boom in Nixa and Ozark, often have fill valves that have simply worn out their internal seals after decades of use.
Hairline cracks in the porcelain are the one thing worth calling someone about right away, rather than troubleshooting further on your own. They tend to show up as a damp line down the outside of the tank or a small puddle at the base that reappears no matter how many times you dry it. A cracked tank will not get better, and if it lets go fully you are looking at a flooded bathroom floor, which on a slab foundation, common throughout Christian County, can mean water finding its way under nearby flooring before you notice.
Why this matters more in winter
A toilet that runs a little all night wastes water and adds a bit to your bill, but it is a nuisance more than an emergency for most of the year. Where it gets more serious around here is in January and February, when overnight temperatures in Nixa can sit well below freezing for days at a time. A toilet with a bad fill valve or a slow leak keeps water moving through supply lines that would otherwise sit still, and in a poorly insulated crawlspace or an exterior bathroom wall, that constant small flow can actually be the thing standing between a pipe freezing solid and one that does not.
So a phantom flush is not just an annoyance to fix when you get around to it. If yours has been running for a few weeks and you have not looked at it, do it before the first hard freeze, not after. Once ice gets into the equation, a simple flapper swap can turn into a burst pipe behind a wall, and that is well past the point of a weekend fix.