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A Navien brand tankless water heater.

Do Tankless Water Heaters Make Noise?

Tankless water heaters (check out our tankless water heater installation service) are pretty quiet machines, all things considered. Where with tank-based units you might hear such noises like pressurized sediment buildup banging around the tank, the on-demand heating of a tankless water heater eliminates a lot of places where noise can emerge.


Despite having a design that minimizes noise, tankless water heaters are still subject to occasionally getting chatty. Most of the noises are normal and to be expected, but some abnormal noises can point to malfunctions in the unit’s operation that are worth inspecting.


It is important to remember that servicing your tankless water heater without a certification can void the manufacturer’s warranty of your unit. Furthermore, to mitigate any risks that are present when dealing with high-power heating, pressure, and water systems, calling your trusted water heater technician is strongly recommended.


At Pink Plumbing we offer comprehensive warranty and servicing plans when you install a new water heater with us: rest easy knowing your home’s water heating system is being taken care of by our highly-specialized and Navien-certified technicians.


Common tankless water heater noises

  • Banging and hammering noises
    • You might hear banging and hammering noises coming from your pipes and the area around your water heating unit. The good news is that this noise is not usually related to your tankless water heater but to the way your home’s plumbing is fastened and held together.
    • Changes in water pressure in your home’s plumbing will cause fluctuations in flow. Opening and closing faucets in different parts of the house can trigger intense, rapid bursts of pressurized water to travel through the pipes: if the mounts your pipes are attached to are weak or loose, the pipes will rattle and bang into each other or the walls. This noise is called hammering and is a common issue in a household’s plumbing system.
    • While it isn’t a cause for concern regarding your tankless water heater, it is an issue that should be addressed sooner than later as the hammering can weaken the plumbing joints and increases the risk of bursting a pipe in your home. Fixing this is easy: you can buy pipe arrestors at your local hardware store and provide additional structural support to your plumbing. This will eliminate any hammering noise and equally protect your home from burst pipes.


Vibrating and rattling from ventilation system

    • If you hear strange noises coming from the vents and your tankless water heater’s fan, you’re likely dealing with an air blockage somewhere in the system. The typical culprit tends to be the intake fan: debris from outside can make it through and accumulate around the fan and the filter. None of this will make it inside the unit itself, but it can begin to hinder the operations of the water heater’s ventilation.
    • The solution to a blockage is simple: after removing the unit from power, inspect the vents to see if there is any visible blockage. Test the fan by spinning it to see if it’s properly lubricated and free from debris. If there’s nothing blocking the fan but it’s still making noises, consider looking at the balancing of the fan – if it’s slightly off-kilter or the brackets are loose, the fan might be rubbing against the sides of its case or causing the motor to rattle. This can be fixed by tightening the motor body’s connection to the water heating unit or inspecting the down rod for play.


Screeching or ‘kettle’ noises

    • If you are hearing high-pitched noises coming from your tankless water heater, it is fairly safe to assume that there’s a pressure issue in your unit. Screeching noises or whining noises like a kettle makes point to the malfunctioning of a pressure valve at a few possible places.
    • Your TPR (temperature-pressure release) valve could be hindered from opening or closing completely, putting incoming water under pressure. This can happen for a few reasons, the most common of which is from sediment buildup in the pipes and around the valves. Hardened limescale can form around the valve and stop it from fully opening or closing. An important part of keeping your water heating system in good health is to conduct regular flushing and descaling – this is often the solution to valve malfunctions.
    • You may also be experiencing valve malfunctions at the inlet and outlet lines of your water heater. While these can be caused by sediment buildup, they can also happen if the attachments have come slightly loose. This can easily be checked by tightening the bolts and the connections at your inlet and outlet valves.
    • These noises may also be related to the gas intake valve and flow sensor: if either of these are malfunctioning the heat exchanger will fluctuate in power and make irregular noises. This issue should be taken to a specialist as soon as it’s noticed.


Vibration noises

    • The tankless water heater is subject to a bit of vibration when it’s running. With water rushing through and being superheated by the heat exchanger, the force of the flow rate and open flame in the heat exchanger (in gas units) can jiggle the unit around a bit. This is rarely cause for concern: if your water heater is properly-fixed to your wall, small vibration noises and humming are simply part of going tankless. This noise tends not to be louder than the compressor in your fridge (the noise is also relative to the installation and power of your unit).
    • If the noise is a nuisance given the location of your water heater in your home, homeowners can look into dampening mats or insulative boxes that can minimize vibrations. Additionally, ensure your water heater is properly secured to its mount.
    • If the vibration noise is very loud and seems abnormal, plus none of the above options fixed your issue, you might be dealing with a loose heating element (in electric models). If not properly tightened or loose after a few years of use, the heating element in the heat exchanger can vibrate and create a humming noise as it rattles against the body of the exchanger. If the vibration noise is coming from the heat exchanger and a loose element, it is well-worth to contact a specialist to get the heat exchanger properly inspected and serviced.


Popping, sizzling, or crackling noises

    • Whether in tank-based models or tankless units, popping, sizzling, and crackling noises are worth noting and require proactivity. Tankless water heaters are less subject to limescale buildup given their lack of stagnant water, whereas constant heating in a tank allows calcium carbonate to solidify more readily. This being said, all water heaters are subject to limescale buildup and homeowners need to regularly descale and flush their water heating units.
    • Popping, sizzling, and crackling noises usually point to limescale buildup, especially around the heat exchanger. These noises come from limescale forming around the hottest parts of the unit and blocking the heat exchanger from effectively heating incoming water. As a response, the outgoing water is colder and the temperature sensor will raise the heat of the exchanger. Trapped moisture inside and underneath the limescale will evaporate and become highly-pressurized until it leaks out around the sides of the piping.
    • If these noises are being caused by limescale buildup, a full-scale flush and descale is required. It is recommended to do this with your home’s plumbing at the same time if possible, as limescale buildup in your pipes will hasten buildup in your water heater. Left unattended, significant buildup can cause flow concerns (which can turn your tankless water heater off), create pressure risks, and even crack pipes. To avoid leaking and internal damage to your water heating unit, take note of popping noises and deal with them quickly.
    • Popping and sizzling can also imply a small leak or a buildup of excess moisture on the surfaces of the water heating unit. The nature of the tankless water heater means it is constantly undergoing large shifts in temperature, rapidly heating and cooling as it turns on and off on demand. If ventilation systems are not in optimal health, the heat exchanger is too hot, or a small leak has formed, excess moisture can condensate on the unit’s surfaces and drip onto the heat exchanger, causing sizzling noises as they evaporate instantly.
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