The Boiler Room Blog

Advice on commercial water heater selection, maintenance and safety issues for businesses that rely on a steady supply of hot water.

Early Signs of Water Heater Failure

early signs of water heater failure

You may be able to prevent a water heater failure emergency situation before it happens.

If you run a restaurant or a hotel and you’re experiencing no hot water for your dishwashers or your showers – it can be a panic situation. Remember: your commercial water heater is a mechanical piece of equipment. So it’s not a matter of if, it’s a matter of when your water heater will eventually fail. Look for these early signs of water heater failure.

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The good news is that you can stay ahead of the game by recognizing the visual signs and the auditory signs that your water heater is about to fail. These signs indicate your water heater might be on its last legs – so if you’re experiencing these symptoms, it’s time to get your commercial water heater checked out by a trained water heater technician.

Signs You Can See:
Advance Visual Signs of Water Heater Failure

Visual Sign # 1: Dripping Water

When you see some water on the floor near your water heater, it’s potentially leaking from two different places – and it’s very important you understand the difference.

hot water heater failure

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Possibility # 1 (T&P Valve): When you see water on the floor near the side of your water heater and/or dripping from the pipe that runs down the side of that unit, this means your temperature and pressure (T&P) valve is venting excess steam. This steam condenses into water, which travels down that pipe and into your floor drain, preventing your water heater from exploding. This is normal. NEVER tamper with or block the T&P valve or pipe. Proper operation of the T&P valve is critical to safe water heater operation. If you’re concerned that there’s a large volume of water coming from that pipe (or elsewhere), it’s time to call a trained water heater technician.

Possibility # 2 (Leaker): When water is leaking from the base of the water heater (or if you notice water on the floor under the water heater), that means your commercial water heater is leaking internally. So your water heater is losing the water it’s supposed to be heating. This can happen slowly over time, or very abruptly. This is because when that water heater tank heats up and cools down, the metal expands and contracts. Over time, hairline cracks can form in the tank itself or in the flue tubes inside the water heater, causing water to leak out onto the floor.

In the commercial water heater industry, there’s a reason we call a failed water heater a “leaker.” When that water heater is leaking water from the bottom of the tank, it’s a sure sign you’ve got a leaker – meaning your water heater is about to fail completely, and soon.

Visual Sign # 2: Corrosion

If you notice a lot of corrosion around the pipe fittings attached to your commercial water heater, this indicates that water is leaking through what should be sealed pipe fittings. Pipe fitting corrosion occurs because mineral deposits from the water are seeping out through the gaps in those pipe connections. This is often called a “slow leak,” which means your water heater might be able to limp along for a while, but it could definitely fail if the problem isn’t addressed.

Visual Sign # 3: Burn Marks

If you see burn marks on the bottom of your water heater, that’s typically an indication of two possible problems.

Problem # 1: Burn marks could mean improper water heater venting is causing backdrafting. This is a serious problem that requires urgent attention and repair because this means you’ve got natural gas and exhaust fumes that aren’t exiting your building, as they should. Instead, those toxic fumes are seeping into your establishment. Not a good situation.

Problem # 2: Burn marks can also indicate that the flue pipes (located inside water heater) are blocked or damaged. This is also a potentially unsafe situation, so that water heater will need to be replaced – and soon.

Visual Sign # 4: Yellow Flame Color

While your water heater is running, you’ll notice a nice, blue colored flame underneath the tank, heating up your water. Now if that pilot light flame is real yellow or orange instead of blue, this is an indication that the burner isn’t working properly and the unit needs to be serviced. Much like the light on the top of your gas stove, a yellow hued flame means it’s burning too cool.

Signs You Can Hear:
Advance Auditory Signs of Water Heater Failure

Auditory Sign # 1: Do I Hear Popcorn?

The most obvious auditory signal that your water heater is about to fail is when it starts to sound like a popcorn machine. This popping noise is from an accumulation of honeycombed mineral sludge, caused when that water heater has to take on hard water. Water trapped in that honeycomb becomes super-heated, and it flashes off into steam. That flash-boiled water is causing those pop POP pop noises. Eventually that sludge is going to stress your water heater tank, causing a leaker – and you’ll need a replacement commercial water heater.

Those loud popcorn sounds are also a sign that it’s time to invest in a water softener! Without a water softener to filter out that mineral sludge and gunk, your water heater tank becomes extremely inefficient and more prone to a shortened life and impending failure.

Auditory Sign # 2: Loud Blower

If your water heater setup has a blower motor attachment on the water heater itself, and that blower motor is noisy and just plain LOUD, that means the blower bearings are about to fail. Here’s the thing: when that blower motor dies, your water heater won’t work. Why? Because your water heater is equipped with a failsafe mechanism that prevents operation in case of blower failure.


So the moral of the story is when you know and understand the visual and auditory signs of looming commercial water heater failure, you may be able to prevent a zero hot water emergency situation before it happens. The more you know about your commercial water heater, the more likely you’ll be able to stay in hot water, and the better off your business will be in the long run.


All images in post are licensed for used under the Creative Commons.

6 Responses to Early Signs of Water Heater Failure
  1. can you tell me if your pipes seem to be under pressure and you turn off the water suddenly and it makes a loud sound, would that cause the water tank to fail.

  2. you mention a “honeycombed mineral sludge”. my water heater seems to be “spitting out” a sweet sticky substance at the bottom where the valves and other wires are located behind a removable metal guard covering this area. my plumber has never seen anything like it and thinks that i may have spilled something sugary on the heater. (not likely at all) what is this substance and why is it coming out of my water heater?

  3. Antonia, here’s our best guess: When you say “located behind a removable metal guard covering this area,” it might mean there’s a gasket leak in that area and the water may be combining with the insulation of the tank. The insulation (especially on older equipment) when wet can become sticky.

    This is just a guess though. We officially recommend you seek the advice of another plumber who can do a more thorough inspection on site.

  4. My hot water heater makes a sssssss sound like it is relieving pressure. Is this dangerous? What can I do ?

    • That’s a noise that should definitely be investigated by a professional in person, because it could mean different things. It could indicate that your heater has developed a small leak at the bottom – water dripping onto the burner can cause a flash boil which makes a noise similar to what you’ve described. Unfortunately, if you have a leaking water heater, it will need to be replaced and it’s best to replace it before that small leak gets bigger and the whole bottom drops out. Alternately, water heaters do have an important part called a T&P (Temperature & Pressure) Valve, designed specifically to relieve excessive pressure as a safety precaution. However, the noise you describe is not a noise that valve should make, so if the noise is originating from here you need to call a plumber to inspect your heater for trouble that could be causing a pressure buildup (which yes, can be dangerous), and/or to determine if that valve needs to be replaced. In either case, your concern is valid and we recommend having a professional inspect your equipment as soon as possible to prevent a bigger issue. Good luck!

  5. My water heater has been dripping water recently. I don’t know what that means but I am happy to know that I should get it looked at. I like that you mention the differences for the leaking so that I can explain it to the plumber when I call him!


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