You cannot see most of what is in your water. You can see what it leaves behind. These are all photographs from our own jobs.
Calcium and magnesium come out of solution as water heats, and over years they solidify into something closer to rock than sediment. It sits in the bottom of the tank, takes up volume that should hold water, and puts a layer between the burner and what it is trying to heat. The unit works harder for less hot water.
Flushing a water heater once a year helps and is worth doing. Treating the water before it gets there is what actually addresses the cause — and it protects every other fixture and appliance in the house at the same time.
Iron-oxidizing bacteria are a nuisance problem rather than a contamination one. What they cause is staining, dull laundry and a distinct smell. They are common on wells.
The buildup in this photograph was thick enough that we had to snap the drain port off the tank to get at it.
Sediment works its way in on private wells and municipal water alike. It collects in aerators and shower heads and chokes the flow, and in bad cases blocks a fixture completely. The photographs here are extreme, but every one of them started as a house where nobody had noticed anything yet.
This is why we recommend a point-of-entry sediment filter more often than any other single piece of equipment. It is the least expensive thing on the list and it protects everything downstream of it.
Chlorine does necessary work in the distribution main. By the time it reaches your house it has nothing left to disinfect, and what it works on instead is the rubber inside your plumbing — gaskets, seals, supply line washers, the flapper in your toilet tank.
We have pulled five-year-old toilet gaskets off chlorinated supply that came apart between our fingers. It is not a dramatic failure. It is a slow one, and it shortens the life of parts that should last a decade.
None of these will flood your basement tomorrow. What they do is take years off equipment you have already paid for, and they do it quietly. Treating the water is usually cheaper than replacing the things untreated water wears out.