Why Is My Water Heater Hissing?

October 06, 2017

If your water heater is hissing, you most likely have one of 2 issues:

  • Too high water temperature
  • Sediment buildup

We’ll explain both of these issues and what you can do to stop the hissing noise. With that in mind, either problem more times than not requires a professional plumber to repair your water heater

Need a professional to repair your water heater? Just contact us.


Issue #1: Too high water temperature

If the temperature of the water inside your water heater is too high, it will force your TPR valve to open and release some of the internal pressure, which can cause a hissing sound.

Look for your TPR valve either on the top of the water heater (seen above) or on the side of the tank.

You see, the higher the temperature of the water, the more pressure builds inside the water heater tank. And when the pressure inside the tank hits a dangerous level, your TPR valve is designed to automatically open and dump out hot water/steam which releases pressure.

The temperature at which your TPR valve activates and opens depends on the water heater model. But to help give you an idea of “safe” levels, TPR valves on Rheem water heaters are designed to activate when:

  • Water temperatures in the tank exceed 210° F 
  • Pressure levels in the tank exceed 150 PSI (pounds per square inch)

What to do:

Have a professional determine why the water heater is producing unsafe temperature and pressure levels. They’ll be able to fix the root problem but also replace your TPR valve (most TPR valves will need to be replaced after they activate and discharge hot water/steam). 

Issue #2: Sediment buildup

Over time, dissolved minerals (calcium and magnesium) in your home’s water settle on the bottom of the water heater tank. And eventually, this layer of minerals builds creating “sediment buildup”.

The bad news: If you’re a Florida homeowner, you most likely have sediment buildup in your water heater. 

You see, Florida has “hard” water (that is, water with a high amount of minerals dissolved in it). Which means, Florida homeowners can expect sediment to build in their water heaters faster than in other areas with “soft” water.

But how does sediment buildup cause a hissing noise? Well, as minerals settle and create layers of sediment, water gets trapped between the layers. As the trapped water heats, it turns into steam which hisses as it pushes upwards and escapes forcefully from the sediment.

What to do:

Have a professional “flush” your water heater regularly. A water heater “flush” means that your tank is drained, sediment is carefully removed and the tank is refilled.

Need help from a Florida plumber?

If you need professional help getting your water heater to stop hissing, we’re here to help.  Just give us a call and we’ll send a reliable plumber over right away.

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