What you're probably noticing
The water heater is making a sound it didn't used to make. A low rumble or a tapping, almost like something is boiling inside the tank, especially right after it kicks on. Maybe the hot water takes longer to show up at the tap than it did a year or two ago. Maybe you've just noticed the unit is only six or seven years old and you assumed you had another decade before thinking about it.
None of that points to age. It points to what's built up inside the tank, and in Nixa, that buildup happens faster than most homeowners expect.
Why Nixa's water is the real culprit
Water in this part of the Ozarks comes out of limestone country. Limestone dissolves into water as it moves through it, and that means the water arriving at your house carries a lot of dissolved calcium and magnesium before it ever reaches your meter. That's hard water, and most of Nixa and the surrounding area sits well into the hard to very hard range.
Every time that water heats up in your tank, some of those minerals drop out of solution and settle to the bottom as scale. Over months and years that layer thickens into a crust. It insulates the burner or lower heating element from the water it's supposed to be heating, so the heater works harder and longer to do the same job. The rumbling noise is literally that layer of sediment boiling and shifting under the water above it.
More on this from Reading List Why Hard Water And Not Age Ends Most Tanks.
What that does to the tank over time
A thick layer of scale doesn't just waste energy. It traps heat against the bottom and sides of the tank itself, which stresses the steel and the glass lining inside it in a way the tank wasn't built for. That's what actually cracks linings and wears through metal years before a water heater's rated lifespan. A heater that should run twelve to fifteen years can start failing at eight, and it's almost never because the unit was defective. It's because of what accumulated inside it, unnoticed, one heating cycle at a time.
This matters more in homes built in the 80s and 90s around Nixa, which make up a good share of the housing stock here, because those original units have often been replaced once already without anyone changing the water feeding into them. A new heater dropped into the same hard water conditions just starts the same clock over again.
What you can check yourself
Pull the drain valve at the bottom of the tank once or twice a year and let a few gallons run into a bucket. If what comes out is cloudy, gritty, or has visible flecks of white or gray sediment, that's scale breaking loose. Clear water is a good sign. Gritty water means the buildup has already started.
Listen for that rumbling or popping sound, particularly in the first minute after the burner or element engages. It's one of the clearest early signs of sediment on the tank floor. You can also check your water heater's temperature setting. Anything set above 120 degrees accelerates mineral drop-out, so turning it down slightly can slow the buildup without making a noticeable difference in your shower.
If your home has a water softener already, check that it's actually cycling and using salt. A softener that ran out of salt months ago is giving you none of the protection you think it is.
Where this stops being a DIY job
Draining a few gallons for a look is safe and easy. Flushing the tank completely, which means fully draining it and running water back through until it's clear, is where things get more involved, especially on a tank that hasn't been flushed in years. Old valves can seize or fail when you try to open them, and a tank with years of scale can have sediment packed solid enough that a standard flush doesn't fully clear it.
If you're hearing that rumble, seeing sediment in drained water, or noticing a drop in hot water volume, that's the point to get someone to look at it rather than wait. A full flush done properly, or a decision about whether the tank is too far gone to bother, is worth getting a second opinion on before you're standing in a cold shower figuring it out the hard way.