HOT WATER - FAQ and Information
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INDEX - Jump to HOT WATER TOPICS
EFV - Excess Flow Valve |
HEAT TAPE - keep pipes from freezing - requires electricity |
Hot Water |
Hot Water Heaters |
Recirculating hot water system |
Rinnai Tankless Water Heaters |
TANKLESS Water heaters |
Water Temperatures - DESIRED |
Water Temperatures - DISH WASHER |
Water Temperatures - SCALDING |
Rinnai RU98e Tankless Hot Water Heater |
HOT WATER
Almost all world-wide safety organizations have come out in favor of setting
your home Hot Water Heater to 120 degrees Fahrenheit (not higher than 120).
You may want your Dish washer to use 140 Degrees Fahrenheit, IF trying to remove
stubborn food from dishes, but 140 Degrees Fahrenheit on human or animal skin will
probably cause dangerous scalding, and should be avoided.
Setting your water temperature to more than 120 degrees Fahrenheit, may cause
scalding, especially for children or older adults (as they may not get out of the hot
water in time to prevent scalding (which create skin burns).
Many Dishwashers, such as our Maytag, have a HEATED WATER setting,
which will, in my case, wash my dishes with water heated to 140
degrees Fahrenheit.
WATER TEMPERATURES - SCALDING
I am NOT Responsible for any Errors - Use at your own risk
I ASSUME NO LIABILITY - You do things at your own risk
Always check facts for your self.
Scalding is a burning from heated fluids such as boiling water, steam, or home
hot water heating systems. Children are the most likely to be scalding by hot
water. Scalding can cause dangerous or even fatal burns.
Scalding Tables and Charts
Images for scalding water temperature chart
Time and Temperature to Scald
Scalding from Hot Water - PSEG.com
Make sure your water heater is set to a safe temperature for home use.
Use the industry charts below to provide guidance to avoid scalding.
Check the water temperature before placing a child in the bathtub.
Never leave a child alone or with other young children in the bathtub.
Always check facts for your self.
Most water heaters are unlikely to scald an adult occupant
(because the adult will get out of the water, UNLESS incapacitated)
Table of Hot Water Scalding Temperatures and Length of Exposure:
Water Temperature Exposure Time Effects of Exposure to VERY Hot Water
Water at 100 degF or below See Safety Note
Water at 120 degF 5 minutes 2nd & 3rd degree burns on adult skin
Water at 130 degF 30 seconds 2nd & 3rd degree burns on adult skin
Water at 140 degF 5 seconds 2nd & 3rd degree burns on adult skin
Water at 150 degF 1.5 seconds 2nd & 3rd degree burns on adult skin
Water at 160 degF .5 second 2nd & 3rd degree burns on adult skin
degF = °F = Degrees Fahrenheit
Safety Note: Hot Water Scald Burn Warning for Infants, Children, & Elderly:
Great care must be taken when exposing infants or children to warm or hot
water as they can be badly burned quickly and at shorter exposure times.
WATER TEMPERATURES DESIRED
I am NOT Responsible for any Errors - Use at your own risk
I ASSUME NO LIABILITY - You do things at your own risk
Always check facts for your self.
The consensus seem to be that you want the temperature of your household
hot water to be 120 Degrees Fahrenheit. You may want your Dish washer to
use 140 Degrees Fahrenheit, IF trying to remove stubborn food from dishes.
My dishwasher has an "HIGH TEMP WASH" option which raises the dish
washer water temperature from 120 Degrees Fahrenheit to 140 Degrees
Fahrenheit. Of course, using the HIGH TEMP WASH will also raise my cost of
electricity to clean dishes.
Raleigh, North Carolina, USA, LAW requires water heater installers to set the hot
water temperature to 120 Degrees Fahrenheit.
There are hundreds of national and international standards set forth by the
major plumbing code making bodies, which specify a maximum temperature of 120°F
for delivered (the water temperature at the faucet) hot water.
As with any hot water heater, the further the heater is from the output faucit,
tub, shower, wash basin,... - the longer it takes to get hot water at the desired
temperature at the desired faucet.
As a waterless hot wate heater is MUCH smaller than a conventional hot water water,
some home-owners have the new tankless water heater installed closer to the location
of the faucets - to enable them to get hot water sooner.
All hot water pipes should be insulated to cut down on wasted heat.
If you have the space and the money, you can have a recirculating hot water system
installed - it cuts down on the time that you have to wait until you get hot
water at the faucet, but it also increases the cost of your hot water.
WATER TEMPERATURES - DISH WASHER
Always check facts for yourself.
The consensus seem to be that you want the temperature of your household
hot water to be 120 Degrees Fahrenheit. You may want your Dish washer to
use 140 Degrees Fahrenheit, IF trying to remove stubborn food from dishes.
My dishwasher has an "HIGH TEMP WASH" option which raises the dish
washer water temperature from 120 Degrees Fahrenheit to 140 Degrees Fahrenheit.
Of course, using the HIGH TEMP WASH will also raise my cost of electricity.
Thus I can keep my water heater set to 120 Degrees Fahrenheit and use the HIGH
TEMP WASH, WHEN needed, to raise the dish wasther (only) temperature to 140
Degrees Fahrenheit when I need to remove stubborn food stais from dishes.
HOT WATER HEATERS
TANKLESS WATER HEATERS
In the USA and even more so in Europe, Tankless water heaters are being installed
more and more often (instead of the conventional hot water heater, which has a
tank in which to store the created hot water).
A tankless hot water heater, as the name implies, has no tank to hold the generated
hot water - instead, hot water is generaterd on demand (only when a hot water faucet
is turned on). It takes more to generate hot water this way, than a water heater with
a tank (the conventional, or most often used in the USA) water heater, but since hot
water is only generated when needed (on demand), instead of all of the time, the
actual cost of hot water generated by a tankless hot water heater is less (than that
of a conventional hot water heater).
ONE MORE THING: It will take slightly longer to get hot water at the faucet, since
the water is not kept, already warm, in the tankless water heater, but is heated
when a hot water faucet is opened.
You should locate the water heater so as to have the shortest hot water pipe runs
(to the place of usage).
I would strongly recommend adding a recirculation pipe/system to ensure that you
get hot water quickly. My Rinnai just needs that pipe (already setup to recirculate
the water to keep it hot.
A suggestion - ensure that your tankless will function, without intervention, after
a power failure or power blip.
My 13 year old Rinnai permanently stores all settings and is fully functional even
after days of a power loss.
If your tankless does NOT save your setting AND it is a plug in, you might consider
putting it on a small UPS (just for power brownouts and blips).
RINNAI TANKLESS WATER HEATERS
While you can always find someone who disagrees, the most popular
tankless hot water heater (at least in the USA) is made by Rinnai.
Rinnai is the highest selling tankless hot water heater in the USA, and is considered
the Cadillac of tankless hot water heaters.
Reports show that you should expect the lifetime of a Rinnai tankelss hot water heater
to be about double that of a typical water heater with a tank (no guarantee, but typical
lifetimes are supposed to be about 18 to 20 years).
The most effective tankless hot water heaters are deemed to to use natural gas or propane.
Rinnai does NOT make an electric version, listing several drawbacks to such a system
NOTE that sice they use some computerized circuitry, even natural gas tankless hot
water heaters will need some electricity, ELSE they won't run. Thus a tankless water
heater will NOT run during a power failure (I run mine on a whole house standby natural
gas generator, so mine works during a power outage).
NOTE Also that since it turns on only when you use hot water, you will have to run
the hot water a little while to get hot water - THEREFORE, TRY TO POSITION THE
TANKLESS WATER HEATER AS CLOSE TO WHERE YOU NEED HOT WATER.
You may wish to consider adding the recirculation pump option - gives you
"instant" hot water.
Tankless Water Heaters: A Buyer's Guide - This Old House'
https://www.thisoldhouse.com/plumbing/21019184/read-this-before-you-buy-a-tankless-water-heater
Note also, that you can get these with remote controls, if your mounting location is
not convenient to access.
You may need a more capable gas meter - I don't remember and our house has the most
capable residential gas meter, called the RED meter. Your installer will know.
P.S, for our natural gas projects, we found that the actual GAS Company was both
the fastest and the cheapest for our tankless water heater and our whole house
natural gas generator. In fact, my generator installer switched all of his gas
business to the gas company. NOTE: not sure gas company still does this kind of work.
It is possible that the water pipes for your tankless water heater may get too cold
in really extreme weather. Ours is mounted in a room attached to the house that
has 6 inches of insulation. Neverthless, I added HEAT TAPE to the water pipes, as
we have no heat in this room nor any way for heated household air to get into the
room used by the Rinnai tankless water heater.
The Rinnai unit is supposed to prevent itself from freezing, BUT I am talking about
piples connecting to the tankless water heater.
HEAT TAPE/PIPE HEAT - Keep pipes warm in freezing weather - REQUIRES ELECTRICITY
Another thing you can do, in an enclosed space, is to add an INCANDESCENT
(they generate heat - NOT and LED nor a CFL) bulb powered by a $20 cheap
thermostatically controlled switch (Home Depot or Lowes).
The thermostat turns the bulb on at about 38 degrees F, generating heat.
If the water heater is in an inclosed space - this should be enough heat
to prevent freezing.
I use a 100 watt incandescent bulbs. My friends with mountain cablins use
this method - just remember, you need to have functioning electric power
to run the thermostat and light these bulbs.
A pair of 75 watt bulbs might be better, in case one burns out. I test my
bulbs accassionally, by bypassing the thermostat [else it has to be very
cold at the location of the water heater, to trigger the thermostat and
to be able to see that the bulbs(s) are still good].
I had the Gas Company install An Excess Flow Valve, or EFV,
An EFV is a safety device installed on natural gas distribution pipelines
to automatically close and restrict the flow of natural gas in the
event an underground pipe is damaged or if there is a significant
increase in the flow of natural gas to the meter (hurricane/tornado
damage):
Excess Flow Valve, or EFV, automatic safety gas shutoff valve
Rinnai Tankless Water Heaters require 120 volts AC, 60 Hz and less than three amps.
#1 Tankless Water Heater Buyer's Guide - Rinnai
Rinnai says: "Because tankless water heaters provide hot water only when it’s needed,
they can save you up to 40%* on your energy bill. They feature Energy Factors of
0.82 up to 0.96, while tanks are typically 0.60."
We have a 199,000 BTU natural gas Rinnai tankless hot water heater, model RU98e
(REU-KB3237WD-US). The RU98e has a built-in capability of cycling an external pump
at pre-set intervals and temperatures.
The RU98e is supposed to handle 4 showers and some other hot water demands, at the
same time (so says Rinnai, but not seeing that on-online, just now).
Rinnai Tankless Gas Water Heaters have a direct-spark electronic ignition, thus there
is NO pilot light (but electricity is required).
I've never had a calcification problems with my 12 year old Rinnai.
Energy Factor:
0.95 for Natural Gas and Propane
Electrical Consumption:
Normal: 63 Watts
Standby: 2 Watts
Anti-Frost Protection: 168 Watts
RECIRCULATING HOT WATER SYSTEM
If you have the space and the money, you can have a hot water recirculating system
installed. The purpose of this pipe is to cause some hot water demand at the far
end of your hot water pipe run - thus, as an example, every 5 minutes the
recirculating pipe may be activated (automatically), pushing some hot water closer
to your faucets, shortening the delay from when you turn on a hot water faucet to
when you actuall receive hot water at the desired location. Of course, this increases
your cost of having hot water, and requires a recirculating water pump and a few other
related items for it to function.
Do hot water recirculation systems work? - 2007
Hot Water Recirculation Systems -- how much energy waste? - 2008
How to Install a Recirculating System : How-To : DIY Network
OTHER INFORMATION