The number everyone quotes
Eight to twelve years. That's the usual life of a tank water heater, and it's a fair summary of what's printed on the box. Electric tanks tend to sit near the top of that range, gas tanks nearer the middle, and a tankless unit is estimated at 15 to 20 years if it's looked after. A hybrid heat pump tank sits around 10 to 15.
The number is a guide, not a promise. Some tanks are done at six and some are still going at fifteen. What decides which one you get is mostly a handful of things that happen inside the tank where you can't see them, and a couple of habits that are easy to start.
What's going on inside the tank
A tank is a steel cylinder with a thin glass lining baked onto the inside. The lining keeps the water away from the steel. It isn't perfect, so every tank also carries a sacrificial anode rod, a long metal rod, usually magnesium or aluminum, hanging in the water. Corrosion goes after the rod first, because the rod is the more reactive metal. As long as there's rod left, the steel stays safe.
When the rod is used up, the water starts working on the steel wherever the lining has a flaw. From there it's a matter of time. Eventually the tank rusts through, usually at the bottom or along a seam, and it starts to leak. That's the end of that tank. Nothing you do after that point will save it.
What Rowlett's water does to it
Rowlett buys treated water wholesale from the North Texas Municipal Water District, and the district describes that water as moderately hard, with minerals coming from Lavon Lake. Hard water carries dissolved calcium and magnesium. Heat the water and those minerals fall out as scale and sediment. In a tank it all drops to the bottom.
A layer of sediment does three things. It insulates the water from the burner or element, so the heater runs longer to deliver the same hot water. It traps pockets of water that boil and pop, which is the rumbling noise. And it holds heat against the steel on a gas tank, which wears the bottom of the tank faster. None of this is dramatic. It's the slow tax that hard water charges.
The district doesn't publish a hardness figure in grains per gallon that we can point to, so we don't quote one. What matters is the pattern. Tanks in hard-water areas that are never flushed tend to die sooner and make more noise on the way.
The two habits that make a difference
The first is a yearly flush. Draining a few gallons from the bottom of the tank, or draining it fully, carries the sediment out before it sets. It takes about half an hour, and the full steps are in the post on flushing a water heater. It works best when it's done every year from the start, because a layer that has hardened for ten years doesn't come out in a flush.
The second is the anode rod. In hard water a rod can be spent in around three to five years, which is long before the tank itself is worn out. Swapping the rod is an ordinary job, and it's the closest thing there is to extending the life of a tank. Plenty of tanks never get it, because the rod is hidden under a cap on top and nobody remembers it exists. A tank with a drain valve you can reach and a rod you can get at is a tank that can be looked after.
A decade in the life of a tank
It helps to picture the years, because what the tank needs changes as it ages.
- Years one to three: nothing to worry about. This is the time to learn where the shut-off valve, the drain valve and the relief valve are, to note the date on the label, and to start the habit of a yearly flush.
- Years four to six: the anode rod in hard water may already be well used. A check now is a cheap way of buying years. If the tank has never been flushed, start gently with a few gallons off the bottom.
- Years seven to nine: the tank is middle-aged. Look for rust at the connections, water at the base, and a relief valve that weeps. This is also the time to price a replacement, even if you aren't buying yet.
- Year ten and beyond: every year is a bonus and a small gamble. If the tank is above a ceiling, the gamble isn't a good one.
None of this needs a plumber at every step. It needs someone to look at the tank once a year and write down what they saw.
Gas, electric, hybrid and tankless
Gas and electric tanks wear differently. A gas burner heats from the bottom, so sediment there bakes against the steel, and that is one reason gas tanks tend to sit nearer the middle of the range. Electric elements sit in the water itself, so scale builds up on the elements instead, and a tank can outlive an element or two before it fails.
Tankless units don't have a tank to rust, which is why they last longer, but they have a heat exchanger that scales up. A unit with service valves and a flush every year or so can run 15 to 20 years. One without them tends to lose efficiency and then fail early. If you're thinking of one, the tankless installation page covers that.
A hybrid heat pump tank carries a tank, an anode rod and a heat pump, so it needs the tank care plus an occasional clean of the air filter on models that have one.
Myths that shorten a tank's life
A few notions go around that don't hold up:
- "Draining the tank every year wears it out." It doesn't. What wears it out is sediment. The flush removes the thing that does the harm.
- "A bigger tank lasts longer." Not by itself. Size has no effect on the lining or the rod.
- "Turning the heater up fixes the hot water." It makes sediment bake harder and raises the scald risk, and the setting should stay around 120 degrees for most homes.
- "If it's not leaking, it's fine." A tank can be a few weeks from failing with no outward sign, because the corrosion is inside.
- "Tankless lasts forever." It lasts longer than a tank, but it still scales up in hard water and needs a flush.
If you take one thing from the list, take the first one. The flush does more for a tank than anything else you can do without a tool kit.
Warranties don't mean what people think
Most tank warranties run from six to twelve years, and the longer ones come with a bigger tank and a higher price. A warranty usually covers the tank itself, not the labor to swap it, and not the water damage if the tank fails. It also expects the heater to have been installed to code. Read it once and file it. Treat it as a floor on what you can expect, and not as a prediction that a tank will last as long as the paper does.
What to do at each age
At under five years, look after it and leave it alone. A fault at this age is more likely to be a part, such as a thermostat, an element or a valve, and repair is usually the right answer. Check the warranty first, since a young tank may still be covered for the parts.
At five to eight years, a flush, a rod check and a look at the connections extend a sound tank. If there's a leak from the body, that's a replacement.
At eight to twelve years, you're in the window. Price a replacement and decide on a timeline. Think about whether the same size and type is still right, because it's the cheapest moment to change them. The cost guide shows what each kind of swap is estimated at.
Past twelve years, the tank has beaten the odds. It's fine to keep it going, but a leak at this point shouldn't surprise anyone, and it's worth having the price in your pocket.
When to start planning
At about nine years old, start budgeting. At ten, it's reasonable to decide on a size and a type and to know who you'll call. The tank doesn't have to come out that day, but you'll be glad you didn't have to make every decision in a hurry with water on the floor.
Homes that were rebuilt after the December 26, 2015 tornado have heaters that are up to about ten years old and are entering that window now, and the post on rebuilt Rowlett homes covers how to check yours. If the tank is already past ten and showing any of the signs of failure, skip the budgeting and get a price.