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Thread: Hot Water Issues (now its too hot!)- Mixer Part Question (Summer/Winter)

  1. #16
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
    New England


    I really like the no sales tax and no income tax! My condo isn't all that expensive so the property taxes aren't too nasty (compared to many stand-alone houses or some other areas). I worked in MA for a long time, and really hated having to pay them income taxes, stopped when I retired.

    You'll get conflicting answers on what's the best idle temp on a WH. General consensus is 120 will slow or stop most common 'bugs', but 140 will kill them (extended time, maybe not immediately). Should you have some (this isn't too common, but happens), and use the water before they're killed, it can get into the distribution system, and then are MUCH harder to get rid of.

    Certainly, the higher it is, the bigger the potential standby losses are, but that can be somewhat overcome by good insulation of both the tank and the water lines. Having the tank at a higher temp does offer some benefits in that it makes the tank act as if it were larger, helping when you need lots of hot water fast since there may not be time for it to reheat the incoming water enough to be sufficient. Combine that more stable, mixed output with a thermostatically controlled shower valve, and you never notice that the tank's output is cooling off as you approach the end - the local valve compensates.
    Last edited by jadnashua; 10-14-2013 at 10:35 AM.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  2. #17
    In the trades Dana's Avatar
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    Jan 2009


    Quote Originally Posted by Reach4 View Post
    A tempering valve at a water heater is not going to be more efficient. Turning down the hot water heater is more efficient. A point of use use of a tempering valve at a tub/shower can make sense. If a required tempering valve at the water heater is mixing in cold water, I think you would be wise to turn down the thermostat. I would like to hope that you are mistaken about the law where you live. Cite?
    The inabilty to turn down the boiler to DHW temps is exactly the problem. If you turn down an oil boiler to 110F min/130F max it will soon be destroyed by corrosive condensation on the fire side of the heat exchanger plates.

    The IPC 2012 section 607 requires that water heaters in residences have mixing/tempering valves set to no more than 110F, and that the aquastat/thermostat on the heater itself set to the same does NOT constitute a complaint alternative (see 607.1.1) nor does local mixing valves at the taps (607.1.2). Even if the installer is required to set it to 110F doesn't mean that you are required to leave it there though. Most local plumbing codes in the US are based on the IPC. In previous versions the section numbers differ, as do some of the specific temperature requirements, but mixing valves on the output of any water heater capable of being set up to 140F or higher storage temps (basically all of them) has been code for at least the last three versions, making it pretty much code everywhere in the US that HAS plumbing codes. Non-compliant installations are grandfathered in, but have to be brought up to code whenever a new water heater is installed.

  3. #18
    DIY Senior Member Reach4's Avatar
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    Sep 2013


    I found that to be quite interesting. Thanks. They seem to refer to water that has passed through a tempering valve as tempered water. There was no indication that where tempering would be used that the tempering device be near the water heater. This section did not seem to require tempered water to be delivered anywhere. The closest it came was "In nonresidential occupancies, hot water or tempered water shall be supplied for bathing and washing purposes." It said "In residential occupancies, hot water shall be supplied to plumbing fixtures and equipment utilized for bathing, washing, culinary purposes, cleansing, laundry or building maintenance. " That would seem to preclude using the tempered water in a house? That can't be right. Set me straight, please.

  4. #19
    In the trades Dana's Avatar
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    Jan 2009


    What are you, some sort of weasel lawyer or something?

    This stuff is not new- look it up in your own local codes if you don't believe it, or go ahead and choose to parse the letter of code mayhaps a bit too finely.

    Sure, you can put a tempering valve at each location if that's what floats yer boat, but the mixer on the shower/sink whatever is explicitly NOT a code-compliant solution on it's own.

    There is no minimum temp specified for the hot water distributed elsewhere, and it's common to use a single tempering valve (for cost reasons) to control ALL hot water distribution in the house.
    Last edited by Dana; 10-15-2013 at 10:32 AM.

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