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Do Hot Water Heaters Make Noise?

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Noisy hot water heater

Water heaters are relatively simple machines but they’re subject to a lot of pressure and heat, occasionally resulting in weird noises if they’re in need of repairs. Tank-based water heaters are especially prone to being chatty and as a homeowner, it’s a good idea to know what these noises might mean – it could be the difference between calling a plumber to replace your hot water heater or the firefighters

What sort of noises do water heaters make and what do they mean?

  • ‘Hammering’ noises
    • Known as “water hammering”, you might hear a loud knocking noise when water abruptly changes directions in the pipes or hits a closed valve. When the water does this, a pressure surge in the system causes the pipes to move around, knocking into each other or the inside of your walls. Usually, water hammering occurs if the pipes aren’t properly anchored. Left unattended over long periods of time, this impact can deteriorate the valves, pipes, and points of impact, potentially resulting in burst pipes
    • This can sometimes be fixed using a water hammer arrestor to secure the pipes that are moving.
  • Ticking/tapping noises
    • Usually as a result of pressure changes in your home’s plumbing system (abrupt on/offs, etc) or heat trap gaskets in the water heater, ticking and tapping noises are rarely cause for concern. As water at different temperatures moves through the heat trap valves, their rapid open and closing can make ticking noises. If the noise is very loud or an annoyance, see if making a slight adjustment to your tank’s pressure valve will help minimize it. Using water hammer arrestors to secure points that are moving around will also help minimize the effect of water pressure changes in your system. If small, easy adjustments don’t fix this, you can also replace the heat trap valves with smaller fittings.
  • Popping noises
    • Popping noises are always a sufficient reason to chat with a water heater technician. This type of noise points to a build-up of calcium carbonate sediment in the base of your tank. When this build up solidifies into lime scale, it will cover the heating element and effectively insulate it from the rest of the water in the tank. The water will thus not get up to temperature and as a response, the temperature gauge will force a signal to the heating element to get hotter. Trapped water inside of the lime scale becomes superheated. Now too hot inside the heater, the popping you’re hearing is highly-pressurized water and water vapor escaping through cracks of the lime scale and along the sides of the tank. This sort of pressure and superheating poses a significant risk of leaking and explosion: if you hear popping, call an expert.
  • Crackling noises
    • Crackling tends only to occur in tank models as it is usually reflective of condensation in the tank vaporizing on the burner or electrical element. When a water heater tank is freshly drained, it immediately fills up with cold water that is to be heated and stored. This fast transition from hot water to cold water will rapidly cool the air and force warm water vapor to condense into liquid form on the roof and drip down into the tank, evaporating as it hits the heated bottom of your water heater. Usually, hearing the occasional crackling is not cause for concern. If you are hearing it often however, this could mean too much condensation is forming and could point to issues in your temperature settings or pressure valves.
  • Humming noises
    • Humming tends to be an issue related to electrical models of tank water heaters as it signals that the heating element is loosely attached. Whereas gas-powered water heaters heat an exchanger at the base of the tank unit, electrical models have an element that sits in the water to facilitate heating. Water will circulate in a water heater as it is heated: hot water will expand and rise to the top while cooler water is pushed down toward the heating element. If an electrical element is not securely fixed to the tank, this circulatory movement of water can wiggle it around, causing it to vibrate and hum. A simple tightening of the element is usually enough to fix this.
  • Whistling and screeching noises
    • Any sort of high-pitched noises related to your water heater indicate a pressure issue. Screeching noises are closely tied to water flow malfunctions in the water heater. The temperature and pressure release valves could be malfunctioning due to wear or lime scale build up – if you isolate the whistling to your TPR valves, shut the system off and get in contact with a plumber as it means your system is not able to adequately release pressure.
    • This noise could also be related to your inlet control valve. The inlet control valve lets cold water into the heater – if it is partially blocked, water moves through a more narrow space into the heater at the same rate of flow, resulting in higher pressure on the pipes and a high-pitched noise from rapidly moving and pressurized air. For most issues, adjusting the inlet control valve and opening it more will resolve this issue right away by lowering the pressure. If this adjustment does not fix the problem, a plumber may need to be called in order to replace the valve or any areas in your plumbing system that are causing excess pressure.
  • Rumbling noises
    • Rumbling noises from your hot water heater tank point to sediment build ups. In areas with especially hard water, mineral deposits can form more easily in your piping and in your hot water storage tank. These sediments, mostly calcium carbonate and magnesium, can settle at the bottom of your tank and harden into lime scale. Among blocking release valves, messing with the temperature of the tank, and more, the expansion and contraction of water in the tank as it’s heated and cooled can move the sediment around, even dislodging it from the base. When this hardened sediment is dislodged, it floats around the tank bumping into the walls or other chunks of lime scale and making rumbling noises. Apart from making annoying noises, these hardened, floating minerals can also cause structural damage to your tank. If the tank cracks, you could be dealing with flooding or worse – explosions. Regular water heater servicing and descaling will greatly help mitigate this risk.

Related: Can hot water heaters explode?

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