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What Temperature should Hot Water Be?


     By Tieger Plumbing Co. Inc. Plumbing Expert Witness

PhoneCall Sylvan Tieger, LMP, LMFSPC at 718 601 6299

I am constantly asked in court "what is the ideal temperature of hot water."
Q- What should be the ideal temperature setting for a water heater?

A- Depends on the local codes and the applications.

Q- How hot should the water be coming out of the kitchen faucet in the sink 25' to 30' from the hot water heater?

A- Depending on local code but normally a min of 100F (38C).

In Nursing homes or where children are concerned 105F (40.5C) maximum is the preferred temperature.

Also how hot should the water be coming out of the faucet in the laboratory 2' from hot water heater?

A- When in doubt install a Pressure balance/temperature faucet to prevent accidental burns.

For example a lot of installations send the same temperature to the dishwasher/washing machines as to the rest of the home.


A residential dishwasher normally requires 140-160F (60-70C) degrees for proper cleaning. Germs love anything less then 140F (60C).

When doing a combination occupancy like a commercial establishment with residential apartments using the same domestic H/W supply I use a commercial heater giving an out put of 180F (82C) water.

As most licensed plumbers know you need 160F (70C) water for washing and 180F for sterilization in lieu of chemicals. Water below 125F (52C) will allow all types of germs to grow inside the hot water tank (called incubators). So they sued everyone until the manufacturers lowered the residential water heaters to a very unsafe level.

The solution to the temperature dilemma is to use a quality mixing valve to allow VERY hot water to go to the dish washer and laundry machines to actually kill GERMS and use these tempering valves to control the temperature of the water after these devices to go throughout the system.

Now when this hot water does reach a showerbody or faucet you can add the following safety devices that are used with great success called pressure/temperature regulating/valves or balancing valves etc.

What these devices do is protect the user from being scalded when someone else flushes a toilet and the pressure drop is acted upon with no chance of the user being burned.

The same when the hot water is used say in a dish washer this sudden drop in temperature Or pressure will not shock someone in a shower.

Years ago when water was heated by the cave dwellers over a pile of wood in a pot around a camp fire the parents tested the water before throwing a child in. Still a good idea!

ABOUT THE AUTHOR: Sylvan Tieger, LMP, LMFSPC
Sylvan Tieger has passed federal testing for Stationary Engineer and an American Society of Mechanical Engineers course of low pressure Boiler and unfired pressure Vessel inspector as given by Oklahoma University (Federal Boiler inspector and unfired pressure vessel inspector) for the US government.

He does high rise fire suppression systems and pump installations and large boilers continuing his repair business and alterations. He also does commercial, residential, institutional and industrial work. He has continued taking courses and receiving more diplomas in heating and fire suppression training.

He received his master fire suppression piping contractors license.

For the US Postal Service he gave welding safety classes and instructed the safety department how to find cross connections of the potable water systems and did numerous asbestos abatement inspections.

He has completed the Plumbers Local Union 5 year apprenticeship (10,000 hours training).

Copyright Tieger Plumbing Co. Inc.

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While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer. For specific technical or legal advice on the information provided and related topics, please contact the author.