I will soon be buying a new water heater for my home. I want to set the heater to keep the stored water at least 140 degrees Fahrenheit (60 degrees Celsius), and use a thermostatic mixing valve to deliver at most 120 degrees F water to the rest of my house (49 degrees C).

I'm wondering if there are any disadvantages to a thermostatic mixing valve. In particular, do they ever emit loud noises such as a "clunk" when water starts flowing?

(It may well be that there are not really any disadvantages. If so, great!)

If there are disadvantages, advice on how to mitigate them would be welcome.

Note: the water in my home is as soft as it gets. (I live near Seattle, and our water is pretty much melted snow from the Cascade mountain range. The water company actually adds minerals to the water during processing, as water this soft can be slightly acidic and nobody wants water to dissolve plumbing over time.) So, mineral buildup inside the mixing valve should be minimal.

  • Over 2 years from the question, how about an update? Have you installed? Any noise out of it? :) – G. Bay Feb 4 '17 at 21:35
  • It appears to me that there are no significant disadvantages as nobody came up with anything. – steveha May 19 at 5:08

I would say that the advantages are number one, it’s comfort, you’re not constantly going back and forth trying to adjusts to get the right temperature and in the process you probably use less hot water and that being the case it probably saves you some money on energy. Also the main disadvantage, if there’s a problem with it, it’s pretty expensive labor wise and material wise to dig them out from the wall and repair them.

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    Do you have any experience with these valves, such as having one in your house? – steveha Jan 15 '15 at 18:18

One disadvantage i've heard of is that some models may freeze in winter. I'm also not sure that every model comes with a back-flow valve at each intake, that can be a issue depending on the pressure of your system.

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