What Causes A Whistling Noise When Running Hot Water?

Our homes are packed with appliances that work in the background to ensure our lives operate smoothly. We use these appliances every day, whether it’s the water heater, water softener, refrigerator, freezer, washing machine, dryer, or dishwasher. So, when one of these appliances begins to fail, we usually notice. 

However, some of these appliances are tucked away, out of sight. When these appliances begin to fail, we might not notice as quickly. Of course, some problems are more evident than others. 

For example, you might notice a whistling noise coming from your maintenance room while running hot water, so it’s pretty evident that a problem is occurring. But if your water heater is whistling, is it actually a big deal? What causes this sound? We’re here to answer these questions and get you on the right track, so continue reading to learn more!

Common Causes Behind A Whistling Water Heater

A few common culprits cause the whistling noise you’re hearing from your water heater. Some problems are less hazardous than others, but it’s essential to address them immediately. Here are four of the most common reasons why your water heater is whistling:

Cracked Tank

Traditional tank-style water heaters are susceptible to a different set of issues than tankless water heaters. One of the problems that can plague tank-style water heaters is a cracked tank. Generally, cracks occur due to prolonged exposure to rust, which allows corrosion to take over and cause weak points in the tank (which eventually break).

When this is the culprit, the whistling sound occurs due to air escaping or entering through the small gap. 

Loose Drain Valve

Alternatively, the whistling sound could result from a loose drain valve. This particular valve is situated near the bottom of the water heater tank, where you can easily drain sediment. Sediment can cause problems within the tank, so it’s essential to flush sediment out as it builds up. 

However, over time, this valve that allows sediment drainage can become loose. Air can slip by when the valve is loose, creating a shrill whistling sound. 

TPR Valve 

Camco Automatic Temperature and Pressure Relief Valve with Extension Probe and Lever | Features an All Brass Body with a Stainless Steel Pressure Spring | (10473)

In each water heater, there’s something called a temperature-pressure relief valve (TPR valve). This valve serves as a safety feature for the unit, as it allows pressure to escape if it rises too high within the tank. 

A pressurized water tank is typical, but if the pressure exceeds the limit, the TPR valve kicks in to bleed some of that pressure out of the tank and return levels to a normal range. The whistling sound you hear results from the TPR releasing built-up pressure within the tank, where air squeezes out of the tank. 

While the whistling sound due to the TPR valve is normal occasionally, it isn’t a good thing if it regularly happens. When the TPR valve constantly has to bleed pressure from the tank, it signifies a potentially hazardous issue with the tank, as the system isn’t regulating its pressure correctly. 

Worn Inlet and Outlet Connections

There are two connections in a water heater system: the cold water inlet and the hot water outlet. The inlet valve escorts cold water into the water heater for heating, and the outlet valve brings heated water out of the unit to send throughout your home. 

Over time, these connections can deteriorate (especially the hot water side), leading to a whistling sound as air escapes. You might notice the whistling sound from the heater while running the hot water faucets in your home, which could indicate a worn outlet connection. 

Is A Whistling Water Heater Dangerous?

A properly functioning water heater should not emit a whistling sound regularly. While some of the culprits causing the shrill sound are less hazardous than others, it’s essential to address the problem immediately. Think of the sound as a warning of the impending failure of a specific water heater component (depending on where the problem is). 

Once you notice the shrill noise from your water heater, it’s vital that you seek the assistance of a certified HVAC technician or a professional plumber to service the system. Otherwise, the heater could create a hazardous environment. 

For example, the whistling noise can point to excess pressure building in the tank or issues with the TPR valve. Or, it might point to cracks in the tank or sediment buildup loosening the drain valve. While it isn’t commonplace, these problems, if left unaddressed, can cause an explosion. On top of that, in some cases, it’s possible for the pressure can build up high enough to catapult the water heater through the roof when the explosion occurs. 

So, if your water heater is whistling, it’s crucial you don’t dismiss the noise as something simple. Failing to address these issues can have catastrophic consequences, so it’s best to be on the safe side and avoid leaving the problem to fester. Treat the noise as an immediate emergency – call a professional as soon as you notice it. 

How Do You Stop A Hot Water Heater From Whistling?

The correct repair for a whistling water heater hinges on the problem. For example, if sediment is causing issues with the drain valve, you’ll likely need to flush the system and reseat the valve. If there’s a crack in the tank, you’ll probably need to replace the entire tank. 

Or, if the inlet and outlet connections are worn out, they’ll require replacement. If the TPR valve continues to bleed pressure, it indicates a significant problem within the system that will likely require a professional’s diagnosis. 

Once you notice the whistling sound from your water heater, shut it off immediately. Sometimes, you might need to turn off the breaker supplying power to the circuit, but be sure to turn it off. While you won’t have hot water until the issue is resolved, it’s better than dealing with the repercussions of an exploded heater.

When you turn off the heater as you wait for the repair technician, the system has time to cool off before they come to work on it.

Can I Fix A Whistling Water Heater Myself?

While some folks may tell you that addressing the whistling sound from your water heater is fine to do by yourself, we recommend leaving this problem to the professionals. Working with a highly pressurized water heater can be dangerous, so it’s best to have a trained professional handle the repair. 

As a precaution, you should avoid attempting to adjust the system, test connections, clear drains, or work with a malfunctioning water heater. Instead, turn the system off entirely and wait for a professional’s assistance. 

As an extra precaution, you and your family could evacuate your home while you wait for the technician. While turning off the power to a highly pressurized heater minimizes the risk of explosion, it doesn’t eliminate the possibility. So, to be on the safe side, take your family to a park or a friend’s house while you wait for the technician. Although this might seem extreme, it doesn’t hurt to be on the safe side. 

How Much Does It Cost To Have My Water Heater Repaired?

Given the complexity and potentially hazardous nature of repairing a water heater, it’s best to leave the fix to the professionals. The average cost to repair a water heater is anywhere from $203 to $800, with the national average at $501. Of course, the price hinges on the particular repair, as some are pricier than others. 

For example, if you have a crack in your water heater, you’ll probably need to replace the entire system. The complete system and installation usually cost anywhere from $1,300 to $5,000. On the other hand, if you need to repair the valve or drain line damage, it’s usually a straightforward repair that should cost within the average range.

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