Water heater question...

I have looked all through the plumbing code book and it mentions the MAXIMUM a water heater, hot water can be provided, but I could find no where that it mentions the MINIMUM temperature the water has to be.

So if a water heater heats the water 1 degree is it operating as intended, it ‘technically’ is ‘heating’ the water.

Anyone have an information on this?

Thanks in advance…


Of course not.

Michael I agree, then how many degrees does it have to heat it?..Where can I find it written?

I agree, but I cannot PROVE anything different

I you attempting to mimic KEVIN?

Water heaters are rated for how much hot water they can produce in a given amount of time.

Your questions sees ill informed.


I have no idea on any code mention but referencing these and similar standards might be justification for a comment. Now this is discussing direct water temp in the tank at the outlet and then is is acceptable to provide a mixing valve to reduce to desired temp.

You bring up a good point however that I will definitely research more myself. Thanks for the challenge …

A dishwasher requires 120 degrees (not code, there is no code it is manufactures recommendations) and temp at the faucet should not be over 120. So your answer is 120. Now with that being said as soon as you start using an electric water heater tank (not tankless) the temp will drop. You can also adjust the temp on the water which some people do when they are snowbirds. That would require you to remove the cover and check the setting and element.

90 Degrees and above is considered hot water.

Below 110 degrees and bacteria will grow. Manufacturer settings are 120. I think they might be lowering them. I write up anything below 110 and above 125 degrees

Where did you acquire this info?

I would first ask the question.
Is hot water a code requirement?

If you’re asking at what temperature the WH should be set at, I think it would depend on your area.

In Quebec, it has to be at 140 F minimum at the WH to prevent bacterial growth and a mixing valve at the tub/shower to reduce it to 120 F maximum to prevent scalding as per building code.

While in Ontario, just across the river, it has to be at 140 F minimum at the WH with a mixing valve at the WH to reduce the temperature to 120 F to prevent scalding at fixtures as per building code.

Actually the code inspector will inspect temp to make sure it is not over 120. If there is not hot water they will require it to be turned on for the next time they return

Yes, in Florida you must have a water heater. But it mentions nothing about minimum temperature. Here is my dilemma and I am trying to help a client and I am against the Realtors, the brokers, the sellers and the plumbers…

They have this tankless water heater that is a total POS. It is 1 inch pipe reduced to 1/2 pipe and hardly no water pressure is present when two showers are ran on hot at the same time.

It states that at 4 GPM it will provide water it will only provide 20 degrees above the temperature of the incoming line. Here in Florida the water stays relatively warm but can get down to 70 degrees, so at 4gpm it would only be able to provide 90 degree water, according to manufacture specifications.

How can I PROVE this is wrong?


Huh?..how much water they can produce given an amount of time. What is the definition of HOT water?

My question was simple, to the point and articulate. I understand that its over your head. I am dealing with specifics and professionals, so its out of your league. Its ok…

Thanks Marcel and I would totally agree and it makes sense. But I am in an battle and do not want to say…well the guys on the message board said…

Thanks for the information and it sounds spot on, I just cant find it anywhere to support my statement. I thought common sense would prevail, that if water trickles out of the shower when two of them are run at the same time, and the water was only temperate at best, then it would be a no brainer…

Guess I was wrong…:smiley:


Russ, maybe this will help. American Society of Sanitary Engineers standards…

Also, manufactures of tempering valves and water heater manufactures will provide you with temperature ranges.

ASSE 1017: Performance Requirements for Temperature Actuated Mixing Valves for Hot Water Distribution Systems
Publication Date: Oct 5, 2009
SDO: ASSE: American Society of Sanitary Engineering
DOD Adopted ANSI Approved Approved

Temperature Actuated Mixing Valves for Hot Water Distribution Systems (herein referred to as “device”) shall consist of a hot water inlet connection, a cold water inlet connection, a mixed water outlet connection, a thermal element and a means for adjusting the mixed water outlet temperature.


Dimensions of pipe threads, flanges and other connections shall conform to appropriate industry standards.

Maximum Working Pressure

The maximum working pressure of the device shall be at least 125.0 psi (861.9 kPa).

Temperature Range

Inlet Water Temperature Range

The hot water inlet temperature range shall be 120.0°F - 180.0°F (48.9°C - 82.2°C) and the cold water inlet temperature range shall be 39.0°F - 80.0°F (3.9°C - 26.7°C).

Outlet Water Temperature Range

The device shall be capable of supplying the domestic hot water distribution system with a minimum adjustable range of 105.0°F- 120.0°F (40.6°C - 48.9°C), provided the hot water supply temperature is at least 20.0°F (11.1°C) greater than the outlet water temperature setting.


Bert it gives me the temperature ranges…they just SUCK. 20 Degrees above the incoming water temp. It gives them to me, I just cant find a code that says its unacceptable.

Here’s one taken from the IPC…

424.3 Individual shower valves. Individual shower and tub-
shower combination valves shall be balanced-pressure, ther-
mostatic or combination balanced-pressure/thermostatic
valves that conform to the requirements of ASSE 1016 or
ASME A112.18.1/CSA B125.1 and shall be installed at the
point of use. Shower and tub-shower combination valves
required by this section shall be equipped with a means to
limit the maximum setting of the valve to 120°F (49°C),
which shall be field adjusted in accordance with the manufac-
turer’s instructions. In-line thermostatic valves shall not be
utilized for compliance with this section.


thanks Bert…you effort is much appreciated, but I found the MAX in the code, its not the max I am worried about, but the minimum…

I truly appreciate your efforts on this, much appreciated brother.