HOT WATER - FAQ and Information

4/06/2021 - Optimized for Firefox 87.0 (Quantum)

COPYRIGHT 1992 thru 2021 - David R. Woodsmall

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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 120F 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 enure 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 12 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. You 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 genrator installer switched all of his gas business to the gas company. 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 ma talking about piples connecting to the tankless water heater. HEAT TAPE/PIPE HEAT - Keep pipes warm in freezing weather - REQUIRES ELECTRICITY 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 its 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

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