Ask a Green Builder: Why is tankless water heater so noisy?

Doeringtankless_2Question: We recently installed a Takagi TK3 tankless water heater and we don’t love it but were resigned to adjusting to how long it takes for the water to get hot. But we were never told that it would make a loud noise when it operates. Ours is installed outside, well within earshot of the neighbor’s bedroom window. Does anyone know of ways to make it quieter, or if it is possible/advisable to build a housing around it to dampen the noise?

Richard E., Redondo Beach

Answer: From Karen Feeney, green resources manager, Allen Associates:

I did a little research with our project managers, a local plumber who installs them and with Takagi itself, and here is what I found out.

Similar to standard hot-water heaters, on-demand units do make noise as they ignite and heat your water. According to Takagi representatives, the noise level for a TK3 unit is around 55 decibels. The origin and level of this noise can be affected by how the unit was installed — whether the unit was mounted directly on the wall (exposed) or enclosed in a protective box. If it was installed close to a window, some people may be more likely to hear the unit ignite.

First you should determine whether the sound you hear is just the unit heating the water or is due to vibrations of the unit against your wall or echoes within its protective box. You can take actions to absorb the sound and reduce these vibrations or echos. If your water heater is exposed on an outside wall (not enclosed) you can place a foam or rubber mat between the unit and the wall. If your unit is in a protective box, you can insulate the inside of the box with Dynomat, a product used in the auto industry for audio insulation, or comparable materials.

If you need help addressing this problem, call the contractor or plumber that installed your unit to come take a look. Or call Takagi directly and see what other suggestions they may have. Hope that helps!

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(Photo: Tankless water heater installed at the Doering residence, not the brand mentioned above.)

6 Comments on Ask a Green Builder: Why is tankless water heater so noisy?

  1. Gary Davis

    When screws on the cover loosen the tin door vibrates and sounds like a B-17 taking off.

  2. sheila

    hoover, i think that in many areas where it gets C-O-L-D and/or overcast, the tankless and solar are a natural pairing. you will not be able to use solar alone in almost any area, so you need a “backup.” the solar can “pre-heat” the water which then runs through the tankless. if the water is below the temp setting, the tankless kicks it up a notch. if it is above it, the tankless never comes on.
    the takagi was one of the few (as of last year) which could accept INCOMING hot water, so be sure to check for that feature if you are thinking of doubling up.
    also, it is VERY disappointing that the solar thermal rebate program is only going to be available to those currently with natural gas water heaters. anyone who is on, say, natural gas-generated electricity, or propane (in the many areas where natural gas is not available) will NOT be allowed to participate. your industry lobbyists at work!

  3. are they crazy

    We installed on on house in mountains. Water was hot quick and could go one forever – ours was installed in closet outside (where water heater had been) and only could hear it in bathroom that shared outside wall. Saved nearly $300 1st winter on fuel.

  4. Frank

    We installed a Rinnai tankless heater last year and it’s absolutely great. We get hot water very quickly…within :20 …and it is extremely quiet. It’s right outside the bedroom window and I’ve never once heard it! I definately recommend his type of heater…takes up alot less space…and we never run out of hot water.

  5. Hoover

    We thought briefly about a Tankless water heater–thank you for the ‘real world’ commentary–that they are less than satisfactory.
    We intend to install a Solar water heating system eventually, hopefully when the solar water heater pilot program in San Diego goes statewide, we can get a break on the price, get tax credits, AND save energy.

  6. Kabong

    We have a Takagi mounted in our attic. When it lights off you can hear a low whirring in the bathroom and hall directly below, but nothing really noticeable. The remote bathroom fans make more noise.
    I have been in the attic and heard the unit light off, and I would not consider the noise any big deal. However, we do have the unit vented out a stack. If this is vented out one of the side mount vents that may be directing any stack noise towards the neighbors house. Richard may want to revisit how the combustion gas from the unit is vented.