A tank water heater should give you ten to twelve years. Plenty of the ones we pull out around this metro do not make eight.
We are a plumbing company, so we are the ones who get called when it goes. That means we also get to look at what is in the bottom of the tank and what is caked on the element, which is a view most water treatment companies never get.
What scale actually does to a water heater
Hard water carries dissolved calcium and magnesium. Heat it and those minerals come out of solution and settle — on the bottom of the tank, and directly on the heating element or above the burner.
That deposit insulates. The element is now trying to heat the water through a layer of rock, so it runs longer and hotter to reach the same temperature. On a gas heater, the burner fires into sediment instead of into water, and the tank bottom overheats. You get three things out of that: a higher bill, less hot water than you used to have, and a shorter life.
The noise is the giveaway. A heater that rumbles, pops or kettles when it fires is sediment boiling underneath the deposit. It is not about to explode, but it is telling you something.
Tankless units are worse, not better
This catches people out, because a tankless heater is the premium option and people assume premium means immune.
A tankless unit heats water as it passes across a narrow heat exchanger. Narrow passages and high heat are the two conditions scale likes best, so it builds faster and matters sooner than it does in a tank. Most manufacturers require the unit to be descaled on a schedule, and several require treated water for the warranty to stand.
If you are considering a tankless install, find out what your water is first. We will tell you before we quote, not after we fit it.
And it is not only the heater
Scale narrows supply pipework over the years. Narrower pipe means higher pressure behind the restriction, and pressure finds the weakest joint. A fair share of what gets called a leak is a pressure problem with a hardness problem behind it.
Dishwashers and washing machines have heating elements and solenoid valves that scale the same way. So do ice makers, which is the appliance people replace most often without ever asking why.
The expensive mistake
Replacing a water heater that died of scale, onto the same untreated water, and expecting a different result.
The new tank is going in on the same supply, so it will do exactly what the old one did on the same schedule. If the first one lasted seven years, so will the second.
The cheapest moment to fix it
While the water is already off and we are already there.
A water heater replacement means the supply is isolated, the pipework is open and a plumber is standing in the right place with the right tools. Fitting a whole-home system at the same visit costs far less in labor than doing it as a separate job, because most of the labor is already happening.
The same is true of a repipe, only more so. New pipe with treated water going into it starts clean and stays clean.
What we will tell you
Sometimes the heater is simply old and the water is fine. We will say so, replace it, and not sell you anything else.
But we will test the water while we are there, free, because we would rather find out than guess — and because in a city that publishes no hardness figure and blends two different source waters, guessing is all anybody else is doing.