Raising water heater temp uses less water?

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Teamo

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I have a 50 gallon electric water heater. I have the element thermostats set at about 120 degrees. A friend of mine who is a plumber says that if you set the water temperature higher then it takes more cold water to mix the water down to a lower/manageable temperature thus making the hot water last longer. It sounds like it makes sense. Does this sound right?
 

JerryR

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I have a 50 gallon electric water heater. I have the element thermostats set at about 120 degrees. A friend of mine who is a plumber says that if you set the water temperature higher then it takes more cold water to mix the water down to a lower/manageable temperature thus making the hot water last longer. It sounds like it makes sense. Does this sound right?

Bumping up the water heater temperature and install a tempering valve is a great combination to add to hot water capacity.

I have a 50 gallon heater and when I was filling up my garden tub I woukd always run out of hot water. Raising the water heater thermostats to 140 deg and installing a tempering valve where house was supplied with 120 deg hot water fixed my problem.

Without the tempering valve, having 140 deg hot water at faucets has potential to cause severe burns due to scalding
 

Jadnashua

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Residential code generally requires a max of 120-degree water except to certain appliances (like a dishwasher). Since most people don't want to go to the complexity of making that happen, they temper all of the water and is one reason why the better DW have a water heating capability - they clean and sanitize better with hotter water. Where I live, a tempering valve along with a vacuum breaker is required on any new WH to pass inspection. BOth young and old have thinner skin than the rest of us, and can get severe second-degree burns very quickly from water hotter than 120, thus the requirement.
 
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I wouldn't install a tempering valve unless forced too...then would uninstall it as soon as the inspector left. I've seen more than enough of systems limited to 120 F supply. Their delivered temps fall far short at appliances, sink, and shower. Somewhere between 125 and 130 F setpoint has been the sweet spot in various homes I've lived in. This includes tanks and tankless. The higher temp with 50 gal tank worked well to fill a whirlpool tub.

I've been resetting tankless to 130 F and that works well with "homerun" systems. I only set the jumpers back that limit them to 120 F when I'm handing them off to someone else. (I'm not taking responsibility for others being idiots.) The nice thing about having the ability to choose higher temps in a tankless is that for safety sake I can always drop back to lower set points, but I don't have to live with that crap.

I don't object to limiting bath/shower or some sinks to 120 F delivered...but that is a far cry from 120 F at the supply (outlet of the water heater) in most applications. And showers typically lose at least 5 F cooling from the showerhead spray, 10 F or more in aerated designs. Add in 5 F or more of piping losses, newer low flow showerheads, and "enjoy" a lukewarm shower.

Dishwashers wouldn't require nearly as much electrical heat if the runs were properly branched/sized and people knew how to make proper use of them. "Homerun" systems are a major step backward in this regard as they defeat preheating. Using several kWh to heat water is really inefficient unless your water heater is already electric (resistance.) I used the "sanitize" setting to booster to 150 F from 120+ in a prior home, but I always inventoried with truly hot water first--letting hand rinse during load pre-heat the water. I use air dry, because the water is already hot enough to sheet and drain and the dishes are hot enough to dry remaining film.
 

MrStop

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I'm not the OP, but my water heater is set to 140* F with the tempering valve bringing the output temp down to 120*. With this setting, and my new water heater, I have nearly limitless hot water. Is there any further benefit to increase the water heater set point to 160*F? Or, am I just causing an unnecessary energy penalty?

I wouldn't install a tempering valve unless forced too...then would uninstall it as soon as the inspector left. I've seen more than enough of systems limited to 120 F supply. Their delivered temps fall far short at appliances, sink, and shower.

I'm not sure why you wouldn't install one, or even uninstall an existing tempering valve as you could just raise the set point on the tempering valve to a higher temperature.

I don't object to limiting bath/shower or some sinks to 120 F delivered...but that is a far cry from 120 F at the supply (outlet of the water heater) in most applications. And showers typically lose at least 5 F cooling from the showerhead spray, 10 F or more in aerated designs. Add in 5 F or more of piping losses, newer low flow showerheads, and "enjoy" a lukewarm shower.

Good point point to check the delivered temperature.

Dishwashers wouldn't require nearly as much electrical heat if the runs were properly branched/sized and people knew how to make proper use of them. "Homerun" systems are a major step backward in this regard as they defeat preheating. Using several kWh to heat water is really inefficient unless your water heater is already electric (resistance.) I used the "sanitize" setting to booster to 150 F from 120+ in a prior home, but I always inventoried with truly hot water first--letting hand rinse during load pre-heat the water. I use air dry, because the water is already hot enough to sheet and drain and the dishes are hot enough to dry remaining film.

Interesting thought. When I check my dishwasher manual, IIRC, the max inlet temp was specified as 120 degrees. It's a newer, more efficient model. I'm not sure if there is a reason for this outside of potential regulation/safety concerns.
 

Teamo

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I have a 50 gallon electric water heater. I have the element thermostats set at about 120 degrees. A friend of mine who is a plumber says that if you set the water temperature higher then it takes more cold water to mix the water down to a lower/manageable temperature thus making the hot water last longer. It sounds like it makes sense. Does this sound right?
I have been looking at the Honeywell AMX 300 tempering valve. We are planning a major addition to the house in the future so we may end up with different mechanicals for hot water, heat, etc. Right now we have a 50 gallon electric hot water heater. If I get the tempering valve I would like to do a simple install as shown in the instructions, which only uses the valve installed on the hot water outlet with a flexible cross over pipe to the cold water inlet tee. In the future if we do go ahead with our plans we will likely have a different set up and I will re-pipe the tempering valve with a circulator set up like Terry shows in the AM 1 schematic. My question is can I install the valve without an expansion tank and flow checks as shown in the schematic and use a simple set up temporarily?
 

Reach4

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Jadnashua

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The higher the storage temperature in the tank, the bigger the delta T, the more heat will be driven out of it...insulation gets more challenged as the delta T rises (the difference in temperatures between two things). FWIW, all of the tempering valves I've seen are adjustable...they typically come preset to 120-degrees F, but that doesn't mean you have to leave it there. Young children and older people almost always have thinner skin, and it really can be a safety issue.
 
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