Why Is My Tank Water Heater Hissing?
December 15, 2021
Hearing coming from your tank water heater is more than just an annoying minor problem. Hissing is an indicator that you have a problem with your water heater that needs addressing before it snowballs into a bigger—and possibly expensive—issue.
Three main reasons can contribute to your water heater hissing. This article will go over the potential causes and how to solve each problem, whether by yourself or calling in a professional plumber.
- Sediment buildup
- High water temperature
- Internal tank leak
You’ll want to resolve the suspected problem as soon as possible to stop hearing the hissing and prevent damage to your water heater or water damage to your home.
Want the hissing to go away ASAP? Contact Red Cap Plumbing & Air for a water heater repair. We’ll be on time, guaranteed (or we’ll credit you $100 toward your service!).
Your home’s water contains minerals (calcium and magnesium) that enter the tank when it's heating water. The harder the water in your area, the more dissolved minerals will build up in your water heater.
As your water heater heats water, these minerals collect at the bottom of your water heater’s tank. Over time, dissolved minerals can create thick layers that trap water bubbles. If you have too much sediment buildup, you’ll hear a hissing noise when the trapped water overheats, turns to steam, and pushes upward to escape from the sediment forcefully. Eventually, this buildup can cause tears and leaks in your tank if you don’t address it (which we’ll explain later).
In addition to a hissing noise, you may notice a popping sound and a slow water heater recovery time with the sediment buildup.
How to Fix
Contact a licensed and experienced plumber to inspect your water heater for sediment buildup. If there is buildup, they will flush your water heater. A water heater flush is a process that drains your tank, removes sediment, and refills your tank.
Because Florida has hard water, homeowners in the state are especially prone to sediment buildup (unless you have a water softener). To prevent excessive sediment buildup in the future, sign up for an annual water heater flush.
Get an annual water heater flush when you sign up for Red Cap Plumbing & Air’s whole-home maintenance plan (plus repair discounts, water heater equipment discounts, and so much more!).
High Water Temperature
The higher your water temperature, the more pressure will build up inside the water heater’s tank. Your water heater's temperature and pressure (T&P) valve will open if the water temperature gets too hot or the pressure inside the tank gets too high to relieve both, making a hissing noise as it does so.
Your T&P valve has a maximum temperature and/or pressure level. When temperature and pressure levels exceed this maximum, the valve automatically opens and dumps steam to alleviate pressure. The valve acts as the only stopgap for both pressure and temperature, unlike thermostats and overload switches.
How hot is too hot? T&P valve maximum levels vary by model. However, residential water heater T&P valves typically activate when levels reach above:
- 210° F (water temperature)
- 150 PSI (pounds per square inch or pressure level)
High water temperature and pressure levels are dangerous. To determine if levels are too high, you can:
- Look at the T&P valve on your water heater. You can find the valve towards the top of your unit. If it is open, you may see water dripping from it.
- Look at the bottom of your water heater. Do you have a small puddle of water on the floor?
- Use a pressure gauge. You can attach a pressure gauge to your outdoor faucet (AKA your hose bibb) to see how high your pressure level is.
How to Fix
Contact a professional plumber if you notice that your T&P valve is open while following the above steps. The plumber will determine if the valve opened because the water heater is malfunctioning or if the municipality has raised its water pressure.
Internal Tank Leak
Hissing or sizzling sounds can occur when water from the water heater’s tank hits hot surfaces.
Infrequent hissing (e.g., if it only occurs after using large amounts of water) sometimes happens when condensation drips onto a hot surface. If you’re hearing frequent hissing and seeing moisture on or around your water heater tank, it is a sign of an internal tank leak.
As we mentioned earlier, excessive sediment buildup can cause tears and leaks in your tank, wasting a substantial amount of water (and money). If your water heater leaks two gallons per hour, that’s 48 gallons of wasted water per day.
So, if your water bill is higher than normal and you hear a hissing noise, you’ll want to have a professional plumber look at your tank for tears—and fast.
Heads up: Leaking water doesn’t always indicate an internal tank leak. The water may also come from a faulty drain valve, which is the piece located toward the bottom of your tank that technicians use for draining. If your drain valve is responsible for the hissing sound, you can either try to tighten or replace the valve. You might have to contact a professional plumber to handle it for you.
How to Fix
Unfortunately, tears only increase in size, so a tank with an internal leak is usually unrepairable. Contact a professional plumber as soon as possible for a new water heater installation. Waiting too long to address a tank leak can lead to significant water waste, a burst tank, and water damage to your home.
Tired of Your Tank Water Heater Hissing? Trust the Experts at Red Cap To Fix It.
Call us at (813) 963-3056 (Tampa) or (727) 474-8287 (Pinellas) or schedule an appointment online.
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