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

Know these early signs of water heater failure. You may be able to prevent a water heater failure emergency before it happens.

If you run a restaurant, hotel or apartment building, just thinking about a “no hot water” situation might make you panic. No dishwashers or no showers? No thank you! After all, you need hot water to run your business. Remember: your commercial water heater is a mechanical piece of equipment. So it’s not a matter of if your water heater will fail—it’s a matter of when. Eventually, all water heaters fail.

But you can be prepared. Look for these early signs of water heater failure—and learn what to do when your commercial water heater is acting up. Read on!

Skip to the water heater problem you’re experiencing:

Note: This post was originally published on 12/07/12. Due to popular demand, we’ve thoroughly updated this post with more comprehensive and current information. Major update: 9/1/16. Last updated: 10/5/16.

Good news! You can stay ahead of the game by recognizing the visual signs (signs you can see) and the auditory signs (signs you can hear) 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, understanding where your water heater is leaking FROM matters. Failure to understand what to do when your water heater is leaking could result in a dangerous situation.

Here’s what you need to know…

Possibility # 1 (Condensate):

If you notice condensation on your water heater, this is typically normal. However, condensation looks different on standard (atmospheric) water heaters than it does on high-efficiency water heaters .

Most high-efficiency water heaters are “sealed combustion” units that gain efficiency by extending the path the combustion gasses travel within the water heater, slowing them down to make use of as much of the available heat as possible. This process generates condensate as a result, that is then discharged through a condensate drain near the bottom of the tank. So, condensation is a healthy sign for high-efficiency water heaters!

Standard atmospheric water heaters typically do not produce condensate, though drastic differences in temperature between the water tank and the air outside the unit can sometimes result in condensation on the outer jacket. This will happen within minutes of first installing any atmospheric water heater. After that, condensation will typically only occur if all of the hot water is used in a short time and the tank is refilled with water colder than the surrounding air, similar to a cold beverage on a warm day.

The Solution:

Condensation is normal and typically not a problem or an early sign of water heater failure. Be sure your basement or room where your hot water heater is kept has proper drainage.

Possibility # 2 (T&P Valve):

t&p valve

Image courtesy of the Wikimedia Commons – from user JohnnyMrNinja – licensed under CC Public Domain.

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 the 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. A slow drip from the T&P valve 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. (Have you seen the Allstate water heater Mayhem commercial? It’s no joke!)

The Solution:

If you’re concerned that there’s a large volume of water coming from the T&P pipe (or elsewhere), it’s time to call a trained water heater technician. A constant flowing stream can be an indication that the T&P valve is faulty or broken. If the seal has broken, it will leak water, compromising the integrity of this vital safety feature. Again, always call a trained water heater technician if you suspect a problem with your T&P valve. DO NOT tamper with the T&P valve. A T&P valve that is capped, blocked, missing or broken cannot release built up pressure, which could cause your water heater to explode.

Seriously. Watch the MythBusters tamper with a water heater, turning it into a rocket:

Possibility # 3 (Leaker):

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 of a standard atmospheric water heater, it’s a sure sign you’ve got a leaker—meaning your water heater is about to fail completely, and SOON.

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.

Note: Typically, only standard atmospheric water heaters become obvious leakers. Many high-efficiency (sealed combustion) water heaters can become leakers without any advance visual signs. High-efficiency (sealed combustion) water heaters do leak, but these units have the combustion chambers at the bottom of the unit, so when an internal tank leak develops it leaks into that combustion chamber under the tank and can’t be seen from the outside. Instead, the leak will typically extinguish the burner, preventing the heater from firing. Unfortunately, the only solution to any leaker is a replacement. If your high-efficiency water heater is displaying an error code or is “locked out,” refer to your manual for the diagnoses code to help ensure your water heater technician is prepared for your service call.

The Solution:

You’re going to need a replacement water heater. Be sure to call a business specifically qualified to service and replace commercial water heaters. (In the Midwest? Contact Reliable Water Services.)

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.

The Solution:

A slow leak through the pipe fittings or along the bottom of the tank welds is a sure sign of imminent water heater failure. You’re lucky your water heater has a little time left, but don’t delay. You’re going to need a water heater replacement SOON—it’s just a matter of time. Even if the leak “seals itself shut” with sediment, that sediment will also soon crack, and then you’re looking at a full-on leaker. Contact a professional commercial water heater technician.

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. (Note: Burn marks are only an issue for standard atmospheric water heaters.)

Problem #1 (Improper Venting):

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.

The Solution:

If your issue is improper venting, there’s likely no need for water heater replacement—you’ll need to call a plumber to get the venting fixed. However, if the venting isn’t fixed, your water heater WILL fail prematurely (as will subsequent water heater replacements)—so don’t wait! Click here for more information on water heater venting.

Problem #2 (Damaged Flue Pipes):

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.

The Solution:

You’re going to need a water heater replacement. Call a professional ASAP.

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. If that pilot light flame is really 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. (Note: This is an issue for standard atmospheric water heaters only.)

The Solution:

In this case, cleaning or replacing your water heater’s burner is likely the only repair you’ll need. However, if you see a yellow flame in conjunction with burn marks (as noted in Visual Sign # 3 above), that’s usually an indication there’s not enough make-up air available, as it can be a sign the flame is starving for the air it needs to burn hot.

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 standard atmospheric 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 because the sediment layer forms directly above the heating element, so it flashes off into steam. That flash-boiled water is causing those pop POP popping noises.

The Solution:

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 Motor

If your water heater setup has a blower motor attachment on the water heater itself, and that blower motor is unnaturally 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.

Note: All high-efficiency (sealed combustion) water heaters have blower motors. If you have a standard (atmospheric) water heater, unless you may have a hybrid power-vented setup (not common), you mostly likely do not have a blower motor.

The Solution:

Unfortunately, sometimes blowers are just loud. It could be your water heater is simply working hard. Listen for a distinct sound of rattling/tinkling/clinking metal. If that’s what you’re hearing, you may need your water heater’s blower motor replaced.


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 no 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 restaurant, hotel, apartment, or other commercial enterprise will be in the long run.


Featured image courtesy of Wikimedia Commons – licensed under CC Public Domain.

8 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!


Leave a Comment