Good point. 120F is the standard temperature for good reason, set it
there and leave it. Not only does it kill off most nasties in the water,
but it also gives a pretty decent run time when you fill the tub or take
Some fools turned my aunt's water heater way down, it was probably 80-
90F. Filling the tub meant there was no water for anything else, as you
had to open the tap all the way to get warm water for the bath. If you
wanted a hot shower, you couldn't get it. The whole system was grossly
I was more concerned with the lack of hot water and didn't think about
the nasties until later. WH's back up to standard, things are safer and
working like they should.
In my opinion, 120 is too low. You can prevent scalding with the proper
shower valve though. I just turn it to full on and the temperature is
Legionella is an aquatic bacteria that thrives in warm water
environments, and is the cause of Legionnaires Disease. It is commonly
found in potable water supplies, hot tubs, cooling towers, fountains,
swimming pools, etc. and multiplies in warm conditions especially
between 68 – 122 °F. The Legionella bacteria can spread to humans when
Glad you mentioned this, one thing is consistent in what you described
that is not true about HW heaters, that is that everything you
described is open to the air. Most use the same chemicals for water
treatment which some humans like myself are allergic to in the first
place. Cooling tower chemicals have changed in most places to
different chemicals to help eliminate the problem.
The only thing in a HW heater that might present a problem is a zinc
anode, and many new HW heaters are glass coated to eliminate erosion
and do not use Zinc.
105 deg HW is the safest for those who have diabetes and do not feel
things as they should, 102 for infants to prevent burns and
scalding's, 140 degrees F for dishwashers, so that their booster
heaters can raise the temp high enough (180) to kill germs on dishes
etc. So you can set it where you need it for your best interests, and
if you need to for showers and tubs you can buy thermostatically
controlled mixing valves but that brings up additional needs and
I have never heard that to be the case, if it was then the disease
would be consistently high across the nation since you cannot treat it
Yes, if you have a recirc system or in the normal home if you let the
water run unmixed, otherwise the Dishwasher would never see it.
Usually the only time you see it is in restaurants for the kitchen
area's. My home was set that way for years, but we had mixing valves
at every sink. It is a real problem when one has two separate valves,
one hot, the other cold and it has to mix in the sink. I don't know
that it would ever be a viable option in that case.
It is. Huh? It's easily treated. Turn up the damned temperature!
;-) It won't survive above 133F, IIRC.
Dishwashers have heaters. It's usually cheaper to let it boost the
You can mix before the hot faucet.
Our first house (banns second, for that matter) had a domestic water
coil in the furnace ("boiler" that doesn't). Of course the furnace
was set at 180F(+) and it backed right up to the kitchen and the
bathrooms. No mixing valves. The water was *hot*.
The link above is designed to sell ACME Mixing valves, in order for
those to do their job properly all the HWS and HWR lines must be
insulated along with that you need a recirc pump or you are just
wasting money on the mixing valve.
You should also not that the disease was contracted via your lungs,
not your stomach.
In many years of experience in the HVAC commercial and industrial
industry I have yet to see any evidence of bacteria in a closed loop
system, I have pulled down boilers, HW boosters, heat exchangers of
all types and never was their any sign of any growth. Now, that said,
once it hits the air and lingers all bets are off. I have seen growth
in Hot tubs for general use in Hotels and Motels, Swimming pools,
cooling towers of all types. Chlorine is often used to kill it, but
especially in cooling towers there are spots where the water pools and
flows very little. We also used algaecides or other types, plus they
all require constant maintenance, tear down, clean up and repairs if
necessary. This is done for a variety of reason, the least of which is
Think about it. Air? Where in your HW tanks is any air? Air stops
water flow or lowers the flow depending on where the air is trapped
and we used air bleed on lines to eliminate that.
Really? They are designed for say a 40 degree rise. While the
thermostat could be set for 180 deg F and the High limit at 200 deg G,
if the incoming water is only 120 deg F add 40 deg F and the best you
will see is 160 and that is not enough to sterilize the dishes and
pans. Most domestic dishwashers do not publish the deg rise, but the
info is out there. Until people make a fuss it'll never be a big deal.
And it should be.
I'd bet. There's a lot of missing info about that system, was it for
HW heating, forced air? A recirc pump between the coil and a storage
tank, and so on. Whatever, I'd bet that it was an old house and done
Then sanitize, not sterilize. The temperature, coupled with the caustic
detergents do a good job. My KitchenAid goes to 155 degrees.
A dishwasher that has a sanitizing feature uses an extended hot-water
rinse to kill germs. The National Sanitation Foundation has set a
standard named NSF/ANSI Standard 184, which means that dishwashers
bearing this certification kill 99.99 percent of bacteria when operated
on the "sanitize" setting. In order to be certified, they also must
reach 150 degrees Fahrenheit during final rinse. Dishwashers that don't
have this certification most likely don't reach temperatures high enough
to sterilize items.
Commercial Dishwashers (NSF/ANSI 3)
Must achieve a minimum 99.999 percent or 5-log reduction of bacteria
Must reach a final rinse temperature of 165°F for stationary rack
dishwashers and180º F for all other commercial style dishwashers
You might have noticed that for domestic dishwashers I did not set a
min temp setting, ("say")
However, they did not speak to a specified temp rise on the HT booster
temp, which I imagine is that electric coil in the bottom pan.
HW heating. The "domestic coil" is a loop inside the boiler used take
off hot water from the boiler. When the boiler isn't in use, the
water first coming out of the coil is at the boiler temperature, with
is 180F +/-19F, IIRC. That house was built in '72, IIRC. Our second
(same issue but the boiler further from the points of use) was built
Had the same system in my house. Terribly inefficient. On a hot August
night you'd hear the burner fire up to keep that poorly insulated coil
hot. Replaced the boiler with a more efficient system with an insulated
tank indirect heated and got a 40% decrease in oil use.
That cheap insurance would have cost me over $1000 at last years prices.
New boiler saves me about 350 gallons a year. I put in an Energy
Kinetics System 2000.
I'd switch from oil if I had a good alternative. Gas is too far away,
propane is no better.
Understood. When I owned the house, oil was less than $1/gal. The
"insurance" was something like $50/yr.
Our second house (in Vermont), we had switched from oil to natural
gas, not because of cost. Our houses since have been electric/heat
pump. Our current system will probably have to be replaced in the
next few years. :-(
When I read that I see boilers that are quite a bit larger than a
domestic types, but they are high maintenance unless you had a good
water softener or naturally soft water, due to calcium build up in the
I would have set the set point @ 140 during the summer season to save
a lot on fuel, unless you live in a cold area of the country.
Due to efficiency requirements in Calif, there has been a lot of
changes in all types of heating systems.
Yes, retroactive mods. Because of new state laws, and pricing
regulations, since the state sets certain limits of fuel prices for
heating etc. boilers over one million BTU's had higher energy costs,
so we wherever possible re rated the boilers by modifying them, or
replacing them with high efficiency boilers and the state, feds, and
gas company's would pay a portion of the costs if they qualified and
that with the reduced operating costs would ROI in 2 years or less.
We don't have many oil fired systems out here for smaller bldg's. But
there were a lot of gas/oil fired boilers for large bldgs, and if
those were replaced and oil firing done away with, there was a lot of
savings there as well.
When I read of the fluctuating oil prices for the oil used in home
heating in the east, I am real happy to be out here, plus the thought
of a snow storm shutting off the supply, }}}
More than 1M BTU isn't a residential system. That's a little
different but it's still amazing they were forced upgrades.
Were they #2 oil systems or #6? Bunker?
A snow storm wouldn't do anything, other than perhaps taking out the
electricity, which would affect any sort of central system. Worst
case, 275 gallons of oil lasted three weeks.
In Vermont we had wood backup. In NY, we got cold (out three days
once). The best solution was moving South, though. ;-) Though we
were out 30 hours during Snowmageddon (2") two years ago.
I know that, and most of my work was with commercial industrial HVAC,
plus shopping centers, Gov't centers and the like. However, there was
a lot or retrofit programs for both residential and commercial users.
Sad part is that a lot of residential users were never informed, nor
took a look at the Utility companies web sites about it.
I remember #2 oil systems, but not much else. It has been decades
since my last oil conversion job, and or service on them.
Well, I wish you the best this winter. Cold is never fun except for
short periods, when planned.
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