ᐅ Lowering the Hot Water Temperature in a Single-Family Home
Created on: 8 Aug 2022 09:43
I
In der Ruine
Hello,
in many discussions here, I have read that lowering the hot water temperature can save energy because there is generally no risk of Legionella bacteria in single-family homes.
Now the question is, is this also scientifically proven? My wife is really concerned about this and would like to have well-founded expert knowledge.
We have a 300L (79 gallons) hot water tank, three taps that are all used daily, and we also shower every day. In my opinion, lowering the hot water temperature is an economic mistake, and I want to adjust the temperature so that during the hottest showers the water heated in the tank can be used directly without mixing in cold water.
Is this really safe? Our old gas boiler does not have a Legionella prevention program.
Thank you for your evidence-based responses.
in many discussions here, I have read that lowering the hot water temperature can save energy because there is generally no risk of Legionella bacteria in single-family homes.
Now the question is, is this also scientifically proven? My wife is really concerned about this and would like to have well-founded expert knowledge.
We have a 300L (79 gallons) hot water tank, three taps that are all used daily, and we also shower every day. In my opinion, lowering the hot water temperature is an economic mistake, and I want to adjust the temperature so that during the hottest showers the water heated in the tank can be used directly without mixing in cold water.
Is this really safe? Our old gas boiler does not have a Legionella prevention program.
Thank you for your evidence-based responses.
There is both a prohibition on linking here and, in my opinion, it is difficult to provide proof.
Look at it this way: The legislation requires a legionella prevention program from a certain system size onward. Just read the regulation and draw your own conclusions about whether it applies to you or not.
I have never implemented a legionella program and wouldn’t even consider it.
More important is to lower your storage temperature in the first place. You don’t need to store 300 liters (79 gallons) of hot water above 45°C (113°F), legionella program or not.
Look at it this way: The legislation requires a legionella prevention program from a certain system size onward. Just read the regulation and draw your own conclusions about whether it applies to you or not.
I have never implemented a legionella program and wouldn’t even consider it.
More important is to lower your storage temperature in the first place. You don’t need to store 300 liters (79 gallons) of hot water above 45°C (113°F), legionella program or not.
Google it. The first result mentions that Legionella bacteria thrive in stagnant water between 20 and 55°C (68 and 131°F). So, it probably doesn’t matter if you lower the temperature from 50 to 45°C (122 to 113°F). Both are within this range, and the problem only arises with standing water.
In der Ruine9 Aug 2022 07:17I'm still not fully convinced.
For example, what exactly is standing water? If the tank has a capacity of 300 liters (79 gallons) but I only shower with 150 liters (40 gallons) per day, there will always be some residual or standing water left in the tank.
When you read around on Google, for example the statement from the UBA, it doesn't all sound so straightforward regarding the 45°C (113°F).
For example, what exactly is standing water? If the tank has a capacity of 300 liters (79 gallons) but I only shower with 150 liters (40 gallons) per day, there will always be some residual or standing water left in the tank.
When you read around on Google, for example the statement from the UBA, it doesn't all sound so straightforward regarding the 45°C (113°F).
S
SaniererNRW1239 Aug 2022 07:31In der Ruine schrieb:
What exactly is standing water, for example? If the storage tank has 300 liters (79 gallons) but I only shower with 150 liters (40 gallons) every day, there will always be some leftover or standing water in the tank.In the storage tank, there is practically no "standing" water with regular use. Cold water flows into the tank at the bottom, and warm water flows out at the top. This causes a thorough mixing to occur continuously.Well then, take a proper look 😉
Avoid Standing, Warm Water
It becomes dangerous when larger amounts of water remain standing for a long time at 30 to 50°C (86 to 122°F), without fresh, cold water flowing in for replacement. This can happen in drinking water tanks or pipes if no hot water is drawn for an extended period. Problematic examples include branch lines and apartments that remain unoccupied for some time.
So, even in your single-family house, the water may be stored for a while, but because it is regularly drawn for showers and so on, cold fresh water continually flows in.
Avoid Standing, Warm Water
It becomes dangerous when larger amounts of water remain standing for a long time at 30 to 50°C (86 to 122°F), without fresh, cold water flowing in for replacement. This can happen in drinking water tanks or pipes if no hot water is drawn for an extended period. Problematic examples include branch lines and apartments that remain unoccupied for some time.
So, even in your single-family house, the water may be stored for a while, but because it is regularly drawn for showers and so on, cold fresh water continually flows in.
B
Benutzer 10019 Aug 2022 08:57In the heating and plumbing group on FB, there was recently a post about a study showing that at 50°C (122°F) the growth of Legionella stops immediately, and this is not problematic in large apartment buildings. Therefore, everyone should lower their hot water temperature.
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