How Loud Should a Tankless Water Heater Be? The Ultimate Guide for Homeowners

Hey friend! I‘m Lillie Gabler, your resident expert on all things home renovation and repair. As a contractor with over 15 years of experience upgrading bathrooms, tackling repairs, and installing the latest innovations, I‘ve become quite the tankless water heater pro!

These on-demand units provide endless hot water, but noise is a common concern. The truth is all tankless heaters make some sound when operating, but there are ways to keep it at normal, unobtrusive levels. This guide will cover everything you need to know – let‘s get started!

How Exactly Do Tankless Water Heaters Work?

To understand the noise, you first need to know how tankless heaters differ from conventional tanks. Traditional water heaters use an insulated storage tank to heat a set amount of water. Tankless heaters instantly heat water as it flows through the unit, giving you continuous hot water on demand rather than a limited supply.

This on-demand design means no more running out of hot water. But it comes at the cost of some operational noise due to the high-velocity water flow and heating elements activating.

Here’s a quick rundown of how they work:

• Cold water enters and flows past an electronic control board and flow sensor

• Burners or heating elements fire up to rapidly heat the water

• A fan distributes air to make the burners more efficient

• The now hot water exits and flows to your faucet, shower, etc.

• This all happens nearly instantly, so you get continuous hot water on demand

The speed at which the water flows combined with the burners, fan, and other components running creates some noise. Next, let‘s look at the factors impacting just how loud your particular unit might be.

What Factors Influence the Sound Levels?

The noise your tankless heater produces depends on several variables:

Water Flow Rate – Faster moving water equals more noise. The higher your hot water demand, the louder the heater has to work. Using multiple fixtures at once increases the sounds.

Unit Size – Properly sized units run more quietly. Undersized heaters struggle to keep up, running longer and harder.

Model – Build quality, insulation, and noise reduction features vary. Cheaper makes/models tend to be louder.

Age – Internal parts wear down over time, increasing vibrations and noise. Newer units run more quietly.

Maintenance – Lack of annual flushing allows mineral buildup that increases noise over time.

Mounting Method – Improper installation leads to excess vibration and noise transferal. Proper mounting is key.

Proximity – Noise drops 6 dB for every 10 feet of distance. Farther from living spaces = quieter.

Water Quality – Sediment and contaminants in the water supply can increase turbulence and therefore noise.

Upgrading to a larger, higher-end tankless model and having it installed properly will help minimize operational sounds. Proper maintenance and water filtration also reduce noise over time.

What Kind of Noises Should You Expect?

Wondering exactly what normal operating sounds for a tankless heater are? Here‘s what to listen for:

• A low hum or buzz similar to a kitchen appliance

• Occasional gurgling when water flow starts and stops

• Clicking as the burners cycle on and off

• Fan whirring sounds ventilating the heating system

• Brief churning when hot water first activates

Most tankless heaters produce a soft hum in the 40 to 60 decibel range when running – about as loud as a moderate rainfall. By comparison, your refrigerator runs at around 50 dB while a normal conversation is 60 dB.

The key is that the noise, while present, should never be so disruptive that it interferes with everyday household activities or sleep.

Tips to Keep Noise Levels Low

Luckily there are some simple ways to help keep your tankless water heater sounds to a minimum:

• Add sound dampening materials – Acoustic insulation around the unit absorbs vibrations.

• Increase distance – Keep the heater far from bedrooms or living spaces if possible.

• Isolate vibrations – Use vibration pads and flexible hoses to prevent transferal.

• Keep it clean – Flush and descale it annually to prevent mineral buildup.

• Ventilate properly – Follow clearance and venting guidelines for optimal operation.

• Hire a pro – Improper DIY installation often results in excessive noise.

• Check water quality – Use whole house filtration to remove sediment.

• Be gentle – Slowly turn handles instead of cranking water full blast.

With some pro tips, you can keep your tankless water heater humming along at acceptable, unobtrusive levels. Next I‘ll go over when to call in a professional.

At What Point Should You Be Concerned About Noise?

While some muffled operating sounds are completely normal, be on alert for the following red flags:

• Noise loud enough to disrupt conversations or sleep
• Intermittent banging, clanking, popping or rattling
• Squealing, scraping metal noises
• Loud gurgling even at low water flows
• The volume increases significantly over time
• Any unusual sounds unrelated to water flow

You should also be concerned if noises start suddenly or don‘t match the tankless heater‘s past sounds.

Excessive noise often indicates:

• Clogged heat exchanger due to lack of maintenance
• Mineral buildup and sediment
• Improperly sized unit unable to keep up with demand
• Defective part like a failing fan or pump
• Improper installation leading to vibration/transfer

If you notice any of these warning signs, shut off the tankless heater and call a technician to inspect the system. Unresolved noise issues can lead to system damage over time.

How Do Tankless Heater Noises Compare to Traditional Tanks?

On average, tankless heaters tend to be slightly louder than conventional storage tank models. Here’s how the noises compare:

• Occasional vs Constant – Tankless sounds occur only while heating water. Tanks run more steadily.

• Humming vs Gurgling – Tankless noise comes from water flow. Tanks emit bubbles from sediment buildup.

• Capacity Limits – Undersized tankless units get louder struggling to keep up.

• Higher Decibels – Tankless peak noise levels can be louder than tanks when operating at max capacity.

• Location Matters – Tankless sounds are centered at the unit vs tanks which resonate through pipes.

But the noise generated from higher velocity heated water flow in a tankless is well worth the tradeoff for some. Keep in mind tankless heaters are still quieter than washing machines, dryers, and dishwashers.

Weighing the Pros and Cons

Before deciding between tankless and old-fashioned tanks, here’s an overview of the main advantages and disadvantages:

Tankless Water Heater Pros:

• Endless on-demand hot water

• Up to 34% more energy efficient than tanks

• Lower monthly energy bills

• Smaller size saves space

• Long lifespan up to 20 years

Tankless Water Heater Cons:

• More expensive upfront cost ($1000 average)

• Noisy during heating cycles

• Requires professional installation

• Max flow limits with undersized units

• Condensation and temperature consistency issues

Traditional Tank Water Heater Pros:

• Lower upfront cost ($400 – $800 average)

• Simple DIY installation

• Familiar design most are used to

Traditional Tank Water Heater Cons:

• Limited hot water capacity

• Heat losses and higher energy bills

• Large tank consumes space

• Short 10-13 year lifespan

• Risk of leaks as tank corrodes over time

For most buyers, the efficiency, longevity, and endless hot water of a tankless outweigh the higher price tag and noises. But carefully compare the pros and cons to decide what works best for your home and budget.

Maintaining Your Tankless Heater for Maximum Efficiency

To keep your tankless water heater providing hot water efficiently for years to come, be diligent about annual maintenance:

Flush the System – Flushing removes sediment and mineral buildup from the pipes and heat exchanger. This helps reduce noises over time.

Inspect and Descale – Have a technician annually inspect and descale the unit to prevent scale buildup that hampers performance and muffles sounds.

Check Filters and Screens – Clean the inlet filter and screens regularly to allow proper water flow. Clogged filters can lead to increased noise over time.

Confirm Proper Ventilation – Make sure ventilation and clearance guidelines are followed so the unit can "breathe" correctly.

Consider Water Filtration – Whole house filtration reduces particles in the water supply leading to the heater. This allows for smoother, quieter flow.

Address Leaks – Even small leaks in plumbing lines can increase water turbulence and therefore operating noise.

Listen for Changes – Take note if the sounds change over time, which may indicate service is needed.

With annual maintenance and care, your tankless hot water heater will continue operating at peak efficiency with minimal noise disruption.

Choosing the Right Size Matters

One of the biggest factors in noise level is properly sizing your tankless heater to your home‘s hot water demand. Here are some general sizing guidelines:

Home Size | Tankless Heater Size
1-2 bathrooms | Small 18-34k BTU unit
3 bathrooms | Mid-size 80-110k BTU unit
4-5 bathrooms | Large 150-200k BTU unit
Luxury home | Multiple manifolded units

Also account for:

• Number of people and peak usage times
• Flow rate of your fixtures
• Climates that require higher hot water temp
• Future needs if expanding household

Oversizing is better than undersizing, as an undersized tankless heater has to work harder to meet demand. This results in louder operation and reduces efficiency. Consult sizing calculators and professionals to pick the right tankless heater.

Which Brands and Models Are the Quietest?

If noise is a concern for you, seek out units with:

• Multiple insulation layers
• Higher quality copper heat exchangers
• Quieter motors, fans, and parts
• Rubber vibration dampening fittings
• Higher end components and build quality

Some of the quietest tankless water heater options on the market are:

Brand	Model	Avg Noise Level
Navien	NPE-A Series	44 dB
Noritz	EZ98	47 dB
Rinnai	Q Premier	48 dB
Rheem	Prestige	45 dB
Takagi	TM-REU 199 OD	51 dB

Investing in a quality unit from a leading manufacturer is worth the extra cost if noise is a top consideration for you.

Getting Creative with Soundproofing Solutions

For noisy tankless heaters, get creative with sound dampening and noise blocking solutions:

• Build an insulated, acoustic enclosure around the heater to muffle operational sounds.

• Mount mass loaded vinyl sheets on the walls around the tankless unit and pipes to prevent vibration transferal.

• Install thick soundproofing panels on the inside of the water heater closet. Acoustic foam works wonders at absorbing noise.

• Place the unit on vibration absorbing pads such as neoprene, rubber or cork sheets.

• Vent the exhaust through your roof or soffits to distance the sound from living spaces.

• Run white noise machines near the heater installation site to mask low level hums.

With some innovative soundproofing, you can tame even the loudest tankless water heater noise.

The Bottom Line

At the end of the day, some noise from your tankless water heater is perfectly normal. While tankless heaters are louder than traditional water heaters, the sounds are minimal compared to most other household appliances. With proper sizing, installation, maintenance, and some acoustic tricks, the operational noise can be reduced to unnoticeable levels in most homes.

I hope this comprehensive guide gives you confidence that a tankless heater can be a quiet addition that provides your home endless hot water for decades to come. As your resident expert, feel free to reach out if you have any other tankless water heater questions!