Hot water heater temp and legionella

It’s depends on how much you use them, so it’s not easy to say. Tanks with a lot of new water movement tend to gather less growth. Or so I’m told.

Master Plvmber

in Plumbing 7 years and 3 months ago

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stickerhappy | 7 years and 3 months ago

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They say keep your hot water tank at 140+ to reduce the risk of legionella growth but 120 and under is the safe temp to avoid risk of scalding. So a mixer could be used to bring the temp down after it leaves the tank.
Our plumber says a mixer is not really needed and to just turn down the tank temp to 120/125 and says he never heard of legionella risk in a hot water heater, just in cooling towers and that type where the water temp is more ideal for legionella growth.
It also seems like their could be a difference between risking growth in electric vs gas hot water heaters from an article I read.
Any plumbers want to share their opinion?

namahs | 7 years and 3 months ago

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Curious what others have the setting on.. During the summer months, I tend to turn down. Is this a risk?

stickerhappy | 7 years and 3 months ago

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I never thought about it either until another plumber randomly mentioned it.

Master Plvmber | 7 years and 3 months ago

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It’s a real thing, but the larger the tank, the more susceptible to having the bacteria grow and flourish. We tend to keep our multi-family tanks at 140° or higher and use the tempering valve for the residents’ safety. This should not be news to any plumber licensed in the City of New York. To maintain licensure we need to take continuing education classes and this was covered extensively in the last round of courses.

stickerhappy | 7 years and 3 months ago

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Thanks Master Plumber.
What’s qualifies as a large tank? We have a couple 50 gallon water heaters.