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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.)

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