Most people only call a plumber when something is already wrong. By then it's usually urgent, and urgent is the most stressful, and often the most expensive, time to deal with plumbing.
If your water heater has started rumbling, popping, or making a low knocking sound, it is trying to tell you something. Good news: it is usually not an emergency. It is almost always sediment.
If your drinking glasses come out of the dishwasher spotty, if your faucets crust over, if your skin feels dry after a shower, that is not your imagination and it is not your soap. It is the water.
I should say up front that I am a plumber, so you are right to read this with one eyebrow up. But I wrote it anyway, because I spent years at a big Valley plumbing company and I watched how the sausage gets made.
Most people find this page because their water heater is failing and they are bracing for the bill. So I will put the number up top instead of making you scroll for it.