Nobody decides one morning that their water heater is failing. It creeps up. The shower takes a little longer to warm. The tank in the garage starts making a sound like a pot coming to the boil. The bath water has a faint orange tinge you put down to old pipes. Each change is easy to live with, which is why the signs of a bad water heater so often get noticed only in hindsight, standing in a puddle.

The useful part is that most of these signs point to a specific part, and plenty of those parts can be replaced. Below, the warning signs are grouped by how you’d notice them, with a note on what each usually means and whether it tends to be a repair or something more serious.

1. Rust-Colored Water From the Hot Side Only

Brown, orange or reddish water is unsettling, but where it comes from matters. Run the cold tap on its own for a minute, then the hot.

If both sides are discolored, the cause is more likely the water main, city work in the area or the pipes themselves, and our guide to discolored water covers those causes. If only the hot side comes out rusty, the water heater is the prime suspect.

Inside every steel tank is an anode rod, a sacrificial metal rod that corrodes so the tank doesn't. When it's worn away to bare wire, the tank lining is left to do the rusting instead. Catch it at that stage and a new anode rod can slow the damage. Once rust is coming from the tank wall itself, no part will reverse it.

2. Grit, Flakes or Cloudy Water

White or tan flakes in a faucet aerator, a sandy feel in the bottom of the tub, or hot water that looks cloudy and clears after a few seconds all point to sediment. Minerals in hard water drop out as the water heats and collect on the tank floor, and pieces get carried into the plumbing.

On its own this is a maintenance issue. A flush clears loose sediment, and a technician can tell you whether the buildup has gone past what flushing can shift. A heater that's never been flushed in a hard-water area can hold a surprising amount.

A strong sulfur or rotten-egg smell from the hot water is a separate issue, usually tied to the anode rod and bacteria rather than wear, and it's worth its own diagnosis.

3. Rumbling, Banging or Crackling

A tank that rumbles while heating is usually telling you about sediment. Water trapped under the mineral layer boils in pockets and bursts through, making anything from a low rumble to sharp pops. The occasional tick as metal expands is normal. A heater that sounds like it's percolating every time it fires is not.

The noise itself is harmless, but what causes it isn't. Sediment forces a gas burner to work harder to heat through it and lets the steel at the bottom run hotter than it should. On an electric heater, sediment can bury the lower element until it burns out. Flushing early can stop the problem. Once the bottom of the tank has been overheating for years, it's often too late.

4. Showers That Fade or Never Quite Get Hot

There are three versions of this, and each one points somewhere different.

Hot at first, then cold far sooner than it used to. The tank isn't holding as much hot water as it should. The tube that carries cold water to the bottom of the tank may have cracked, the lower element on an electric model may have burned out, or sediment may be taking up room that water should fill.

Never more than lukewarm. On electric tanks, a dead upper element or a failed thermostat is common. On gas tanks, look at the burner flame through the sight window. A tall, lazy yellow flame instead of a crisp blue one suggests a combustion problem a technician should look at.

Swinging between hot and cold. A thermostat or gas control on its way out can cause it. So can a worn pressure-balancing shower valve, if it only happens in one bathroom.

Elements, thermostats, dip tubes and gas controls are all routine replacements. A heater with one of these faults is often perfectly healthy otherwise.

5. Slow Recovery

You run a load of laundry and then wait well over an hour before there's enough hot water for a shower. Recovery time stretches out when heating parts are wearing or when sediment is insulating the water from the heat. It's easy to miss, because it happens gradually and the household simply adapts. If you've started spacing out showers, that's worth mentioning when you book a visit.

6. Moisture, Rust or Crust Around the Tank

Walk around the heater with a flashlight once in a while. You're looking for:

• damp concrete or a ring of water at the base
• rust on the fittings at the top of the tank
• white or green crust on the pipe connections
• rust streaks running down the outer jacket
• water at the end of the relief valve's discharge pipe

Corrosion on a fitting or a weeping valve can usually be repaired. Rust that seems to be coming from the tank body, or water appearing at the base when every fitting above is dry, is far more serious, because a tank that has rusted through can't be fixed.

7. Scorch Marks or Soot Near the Burner

On a gas water heater, look at the area around the burner access cover and the top of the tank where the vent pipe connects. Black soot, scorched paint or melted plastic on the gas control are signs that combustion gases or flames aren't going where they should. That can mean poor venting or a burner problem, and either can let carbon monoxide into the home.

This one isn't a wait-and-see sign. Turn the heater's gas control to Off or Pilot and call for a technician. If anyone feels dizzy, headachy or sick, or a CO alarm sounds, get everyone outside and call 911. Once the heater is fixed, a round of indoor air quality testing, which covers carbon monoxide, can confirm the air in the house is clear.

8. A Heater That Keeps Shutting Itself Off

Pilot lights that go out every few days, an electric heater whose breaker trips, or a reset button that keeps popping are all safety devices doing their job. Something is triggering them, often a worn thermocouple, a failing element or an overheating condition. Resetting it again and again treats the symptom and not the cause.

Las Vegas Water Brings These Signs On Early

Signs one, two and three tend to show up sooner here than in soft-water cities. With a hardness of roughly 290 ppm, or about 17 grains per gallon, local water lands in the very hard range on the Las Vegas Valley Water District's scale, and that speeds up both sediment and anode wear. A water softener or filtration system cuts the mineral load before it reaches the tank.

Repair Comes Before Replacement

A worrying sign isn't a death sentence for the heater. Rust from a worn anode, sediment noise, a dead element, a broken dip tube, a leaking valve and a faulty thermocouple are all fixable on a sound tank. Replacement belongs in the conversation when the tank itself is leaking or rusting through, or when several major parts are failing together.

A good technician will check the tank, anode, burner or elements, controls, venting and valves before recommending anything, and explain which signs are urgent and which can wait.

Having It Checked

Noticing one or two of these signs early is the best position to be in, because the fix is usually a part rather than a whole heater. To have yours looked at, schedule water heater repair with Dr. Cool online or call (702) 873-1800. Visits are often available the same day, and you'll see the price before any work begins.