Although there are exceptions to every rule, here are the basic sounds you may hear and the most common water heater problems associated with them.
Crackling, Popping and Rumbling
Sediments collect around the element tubes of a water heater. When the element is off, the caked sediments trap water beneath them, and the water heats until it makes a cracking or popping sound as it is forced through the deposits. This is more common on older units, and the noise increases as the deposit layer thickens. Clean or replace the element.
Another indication the heater needs maintenance is a rumbling sound, produced by sediments being stirred by the water flow inside the tank. Use a deliming mixture to clean the tank and drain the water heater.
If maintenance does not cure the problem, the noises may be something as simple as the expansion and contraction of the main steel tank or expansion tank during normal operation. Metal pipes can make similar noises in situations where the water is heated beyond about 125 degrees.
The element in an electric water heater is commonly placed vertical in relation to the tank. Water flowing around the element can cause vibrations in this situation, creating a humming noise. Tighten the element slightly to correct the problem.
Knocking or Hammering
A knocking sound in your walls is related to pipes heating internally, and is literally known as “water hammering.” When water entering or leaving the tank is abruptly turned off, it can cause the pipes to move, banging against studs or the interior of walls. This can be caused by a dishwasher or toilet bowl, or by a water pump without a holding tank.
The noise is not dangerous to your water heater, but could lead to eventual wall damage if it is not corrected. Install a water hammer arrestor between the offending device and the water heater.
Singing, Screaming or Screeching
Screaming sounds are created by water being forced through a small opening. This is usually caused by a valve that is not fully opened, either at the water heater or at a particular outlet such as a sink. Check the valves in you water lines (see also ‘How To Loosen A Corroded Water Valve‘).
Ticking or Tapping
Many water heaters have heat traps or check valves installed in the pipes on top of the heater. These traps are designed to prevent water from flowing in the wrong direction in the pipes, and may make ticking or light tapping sounds.
This is normal, but you can replace the heat trap with an ordinary dielectric nipple if it disturbs you. You should also be aware that your plumbing may make similar noises as the hot water in them cools down.
Tankless Water Heater Noise
Tankless water heaters have their own distinct noises. If you hear a clicking noise, this is typically just the flow switch turning on and off to start and stop the flow of water and is completely normal. If it’s making a lot of noise when turned on, it may be because calcium deposits are being left behind due to hard water in your area.
Installing a water softener system may be necessary. Others reasons for a noisy tankless water heater model may be an issue with the burner, the fan may be dirty, or possibly a leak in the sealed combustion resulting in irregular gas combustion. Generally speaking, there is a lower chance of hearing strange noises with a tankless water heater vs tank model.
Water Heater Maintenance
The cure for most sounds associated with your water heater is found in regular care and maintenance. Since minerals in your water lead to sediments in your water heater, installing a water softener in your primary water line will reduce buildup and associated noises.
Similarly, flushing the tank with a deliming solution annually will prevent heavy build up in the tank and serve to keep the elements cleaner as well. Anyone can become a responsible water heater owner with a bit of easy maintenance.