If your home's hot water heater is making an odd whistling noise every time it heats water, you may be wondering what could be causing the strange sound. This whistling is often the sound made when the tank's temperature and pressure relief (TPR) valve is malfunctioning. Besides the high-pitched noise, also look for the following signs that the valve is failing and needs immediate professional attention.

1.  Water Is Leaking from the Valve

The main function of the TPR valve is to keep the pressure inside the tank from getting too high. If there is too much pressure inside the water heater, the tank could rupture or even explode, causing massive damage to the surrounding area. Depending on your water heater's model, it may look like a faucet spigot or a lever.

Examine the valve, and see if there is water leaking from it. If you do see drips or even small streams of water coming from the valve, this usually means that the valve is stuck and not able to release the excess pressure inside of the tank, causing it to push water through the valve.

2.  Water Does Not Come out of the Valve's Drain Pipe

If you do not see any water leaking out of the valve, there could be another issue at play that is making the pressure buildup inside the tank and creating the whistling noise you keep hearing. Over time, the water that is being heated inside of the tank can leave behind mineral deposits, as well as corrode the metal.

If the deposits or corrosion has reached the valve's drain pipe, the excess pressure cannot fully travel through the blocked passageway. To test for this, place a bucket under the valve's opening, then turn on the valve.

If little to no water is coming through the drain pipe, there is most likely something blocking its flow. You should have a professional take a look at the valve and its drain pipe as soon as possible.

If the valve is showing either of the signs above, there is a serious problem that is allowing pressure to build up inside the tank. If this issue is not taken care of as soon as possible, the excess pressure can damage the tank or even cause an explosion. Contact a contractor who offers water heater repair services immediately to have them inspect and replace the valve, as well as fix any underlying issues.