# How Hot Is Too Hot?



## plbgbiz (Aug 27, 2010)

This was sparked by posts on the recent Tankless Maintenance thread. So how hot is too hot? What steps are we taking to minimize risk to our customers? Are we checking what temperature is being provided by water heating equipment? Are we just doing the touch test? Putting the tank on the medium mark and calling it good?

Since I'm not in new construction scenarios, providing two separate hot feeds is seldom if ever an option. Providing separate feeds to the dishwasher and automatic clothes washer would be cool as long as you bypass the kitchen faucet. In my admittedly limited experience, I have _*NEVER*_ seen a residential system with separate hot feeds tempered to different temperatures. It would be cool, but it never happens here.

Let me put this nicely....aw heck there is no way I can put this nicely.

I really don't care about requirements by Bosch or any other fixture manufacturer. It is unconscionable for a professional charged with protecting the health and safety of our society by means of its precious water resources to knowingly provide dangerously hot water beyond what the code allows just because someone is too lazy to dry their own dishes. 

Codes are like stop signs. They are often instituted only after something bad happened. Perfect storms do happen and I don't want to be there when it does. Adjusting water to 140deg when the code says the max is 140deg is like telling your kids they can't play in the street but it is perfectly safe to tap dance on the curb.


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## user2090 (Sep 26, 2009)

I was always taught, and I think its code confirmed, to set a water heater at 120 degrees, or at the factory setting of max 125 degrees. A quick look through Indiana code book, and when talking of shower/combination valves states, a max "Mixed Temp" of 120 degrees, and that the water heater thermostat is not an adequate control. 

I can and possibly will look further into later.


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## Titan Plumbing (Oct 8, 2009)

So, with all this talk about temp. How do y'all know how hot the water is on a new heater? Do you actually stick around for 45 mins to an hour to test the temp? :whistling2:

I know around these parts the thermos don't have degree settings, just A,B,C, hot and very hot, oh and vacation too.


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## PLUMBER_BILL (Oct 23, 2009)

*Set the heater ???*



Choctaw said:


> So, with all this talk about temp. How do y'all know how hot the water is on a new heater? Do you actually stick around for 45 mins to an hour to test the temp? :whistling2:
> 
> I know around these parts the thermos don't have degree settings, just A,B,C, hot and very hot, oh and vacation too.


On a heater replacement I look at the old thermostat setting. That is where I put the new one ... I know this does not meet with the approval of the suits. But is sure saves call backs because the water is not hot like the old one ...


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## Master Mark (Aug 14, 2009)

*people help themselves.....*

what is to stop any one who can read a gas dial from 
turning it up thelselves??? How can I stop them from doing this.... Isnt there already a warning on the heater 
about scalding yourself???

I set them on med and let the customer do whatever thye decide is best for them.... it says so on every invoice ....

if they scald themselves 6 months from now , its really anyones guess who turned up the thermostat..... teh warning is on the heater.....


also , all new homes have to have pressure balanced tub faucets.... they have basically taken over the market and you are faced with less and less of the old stlye faucets out there....

130 is a good average temp ,


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## Phat Cat (Apr 1, 2009)

I think a H.O. should be able to decide what is hot enough for their situation. It's ridiculous to treat adults like children without common sense. I.E. - Two adults living in their home with no children should be able to decide for themselves how hot they like their water. 

As for code, scalding is a possibility but setting it at 120 can allow bacteria to grow as well. I think the preferred temp was 140 for that. Does anyone know how many scalding incidents take place each year?

Whenever we leave a WH set at 120 in the summer, in the fall we get a call that the water is not hot enough and they run out. We will usually show the H.O. how to adjust it themselves.


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## plbgbiz (Aug 27, 2010)

Choctaw said:


> So, with all this talk about temp. How do y'all know how hot the water is on a new heater? Do you actually stick around for 45 mins to an hour to test the temp? :whistling2:


naaaa....we don't do that but we do usually leave it set at the enlarged medium poit on the valve. We then give VERY specific instruction to the homeowner on how to adjust the heat to their liking. My assumption (you know where that leads) is that was a safe area. Whenever we do a water heater inspection, checking the temp at the closest fixture is part of the check list.

It just seemed that purposely shooting for temps over 130 is a bit risky from a liability standpoint. Given the sue-happy world we live in, I would think that an actual temperature reading on the gas valve would be in our future.


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## Redwood (Sep 8, 2008)

I set it to the 120 setting and mark on the invoice that I did so.

Many of the high output units run at a higher setting of course these will have a tempering valve on them.

Many of the systems I see are dhw coils on boilers and those also have tempering valves on them.

I believe in the future we will see water heater temps at 140 F and above there is a lot of talk concerning legionella bacteria and it's prime growth rate being in the water heater setting range which will probably bring changes to codes and tempering valves on all water heater installations in the future. Some places already have this in effect.

At 60 °C (140 °F) - Legionella dies instantly - pasteurisation occurs.
At 55 °C (131 °F) - 95% die
50 to 55 °C (122 to 131 °F) - Can survive but do not multiply
35 to 46 °C (95 to 115 °F) - Ideal growth range
20 to 50 °C (68 to 122 °F) - Growth range
Below 20 °C (68 °F) - Can survive but are dormant, even below freezing


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## Tommy plumber (Feb 19, 2010)

I have read that Florida law sets the limit for domestic hot water at 120 F. Our code states that for a bidet, the max is 110 F. On new construction, the plumber better put a therm. mixing valve on bidet.


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## RealLivePlumber (Jun 22, 2008)

We still see winter summer hook ups for domestic hot water, with no mixing valves. They get like 180 at the sinks.


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## Bayside500 (May 16, 2009)

Tommy plumber said:


> I have read that Florida law sets the limit for domestic hot water at 120 F. Our code states that for a bidet, the max is 110 F. On new construction, the plumber better put a therm. mixing valve on bidet.


i knew we had to put a mixing valve on big tubs now, but also on bidets ?

i am doing a second rough now on a large house that has a bidet, i had better check with my boss about this.


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## plbgbiz (Aug 27, 2010)

Redwood said:


> I believe in the future we will see water heater temps at 140 F and above there is a lot of talk concerning legionella bacteria and it's prime growth rate being in the water heater setting range which will probably bring changes to codes and tempering valves on all water heater installations in the future. Some places already have this in effect.
> 
> At 60 °C (140 °F) - Legionella dies instantly - pasteurisation occurs.
> At 55 °C (131 °F) - 95% die
> ...


RW,
Do these stats take into account the use of soap? Is the water supposed to disinfect by itself? I'm not sure my hands could handle that. In our house, me and Miz Biz wash the dishes by hand so 140deg water for cleaning my ravioli plate is unlikely. I have delicate skin you know. 

Also if I am not mistaken, PVC starts to soften and breakdown at 140deg. It's low temp rating is likely why it can't be used for hot water distribution. That is also why I only recommend DWV copper or CI for drainage in commercial kitchens since the PVC get deformed from the hot water. If we move to hotter residential use, will we have to modify our materials connected directly to the fixtures?


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## Redwood (Sep 8, 2008)

plbgbiz said:


> RW,
> Do these stats take into account the use of soap? Is the water supposed to disinfect by itself? I'm not sure my hands could handle that. In our house, me and Miz Biz wash the dishes by hand so 140deg water for cleaning my ravioli plate is unlikely. I have delicate skin you know.


Biz,
This temperature would only be in the tank of the water heater itself. The concern is the amount of time the bacteria sits in prime growth temperatures reproducing. Water in the pipes is not a concern as it cools off to ambient fairly quickly and that should be out of the range.

All water has the bacteria in it at some level but when the bacteria reaches a high enough level it becomes dangerous.

These levels and action required from wikipedia:


> Legionella bacteria CFU/litre	1000 or less	System under control.
> 
> Legionella bacteria CFU/litre more than 1000 up to 10,000	Review program operation. The count should be confirmed by immediate re-sampling. If a similar count is found again, a review of the control measures and risk assessment should be carried out to identify any remedial actions.
> 
> Legionella bacteria CFU/litre	more than 10,000	Implement corrective action. The system should immediately be re-sampled. It should then be "shot dosed" with an appropriate biocide, as a precaution. The risk assessment and control measures should be reviewed to identify remedial actions. (150+ CFU/ml in healthcare facilities or nursing homes require immediate action.)


The water you are using on your delicate hands would have been tempered...


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## plbgbiz (Aug 27, 2010)

So the addition of BWC's tempering valve with digital readout would be beneficial since the tank could be cranked up to kill the crawlys but be at a safe temp is headed to the fixtures?

I like that a lot better than trying to get 140 distributed through the house.


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## Tommy plumber (Feb 19, 2010)

Bayside500 said:


> i knew we had to put a mixing valve on big tubs now, but also on bidets ?
> 
> i am doing a second rough now on a large house that has a bidet, i had better check with my boss about this.


 
I think this changed a while back, not sure. But if you look at 408.3 in 2007 Florida Plumbing Code you'll see it. Every code cycle things change and it's easy to be out of the loop.


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## plumber666 (Sep 19, 2010)

130's how I roll on HWTs. But I did a seperate 180 system recently at a winery for hosing out wine tanks. Scary hot! Told the owner to put great signs by the hose bibbs, cause, as I told him, it'll blast the flesh right off your body. In service for a couple of weeks now, still no signs.


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## user2090 (Sep 26, 2009)

plumber666 said:


> 130's how I roll on HWTs. But I did a seperate 180 system recently at a winery for hosing out wine tanks. Scary hot! Told the owner to put great signs by the hose bibbs, cause, as I told him, it'll blast the flesh right off your body. In service for a couple of weeks now, still no signs.



That is someone who is just begging for an organization like OSHA to come in and shut them down.


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## Redwood (Sep 8, 2008)

Indie said:


> That is someone who is just begging for an organization like OSHA to come in and shut them down.


Except it would have to be the Canadian version...:whistling2:


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## user2090 (Sep 26, 2009)

redwood said:


> except it would have to be the canadian version...:whistling2:


cosha?


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## Richard Hilliard (Apr 10, 2010)

With our snowbirds and their water heaters set at 120 degrees is an issue with bacteria developing due to the heater not being hot enough to kill the bacteria. I always spend enough time and connect the electric to the water heater and turn it on before I do the relief valve. This allows the heater time to start heating. By the time I flush the lines out in the home and write the invoice it generally is hot enough to test the temperature unless it is a 66 gallon or larger heater. Our water is 76 degree entering the home, it does not take it long to rise to 120.

I just had an elderly couple complain the water is too hot at 100 degrees. What is the age of people where they become more sensitive to the water temperature? We could do an average but this is not true for all people. Hence the problem with higher temps, the heaters used to come preset at 140 degrees before the 90’s and booster heaters in dishwashers.

I show the customer the book that informs them on how to turn the stats up.


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## RealLivePlumber (Jun 22, 2008)

Indie said:


> cosha?


Isn't that the pickle company?
:laughing:


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