Legionnaires disease

Jackz

I have been reading all these posts about open systems being breeding grounds for the bacteria causing legionnaires disease. I have a second home in the mountains in a cold area. We are usually there every weekend but sometimes every other weekend. The boiler is on all the time and hot water is made by an indirect fired hot water tank. I have the water temp on the indirect set at 122 degrees now. Since the water can sit in the indirect for a week without being used what temp should I have the hot water set at to prevent the legionnaire bacteria from multiplying. This hot water is for household use; it is completely separate from the water in the heating system. Thanks.

Mark Eatherton

Continuous exposure to 130 should do it...

The hotter the better, but lab tests have shown that exposing the bacteria to 130 does a good job of keeping the bacteria from amplifying.



Hospitals typically run 140 degree supply water temperatures, and will occasionally experience an outbreak at which point they do a scald sanitization flush of 180 degree F water through ALL taps, which is not only expensive from a cost of operation point of view, but also labor costs because each outlet has to be monitored by engineering/hospital staff to avoid a major law suit over scalding during the flushing process.



It has also been found that due toe stratification in a vertical tank, that electric water heaters held at 140 can still harbor the bacteria in the lower portions of the tanks.



I saw a study the other day that said that 1/2 of the water sources tested in the US proved positive for the legionella bacteria. It can not survive temperatures of less than 50 degrees F, so maybe we are looking at the wrong end of the thermal scale for eradication. Maybe as the water comes in from the street, we need to chill it down to 35 degrees F to kill off bacteria. We can use the heat from that process to preheat the DHW… It is a known fact that well water in the Northeast doesn't contain any of the bacteria. Too cold…



The bacterium is in the dirt. If your surface water source comes into contact with the dirt (i.e. surface storage reservoirs) then it is in the water too.



Kudos to you for being proactive in controlling and containing this deadly disease.



ME

kcopp

I thought....

of you ME and this very thing last weekend. I was in NC to watch some collegiate baseball. My brother lives just outside of Charlotte so we stayed at his place. He has been away since before Christmas....no hot water usage. I made sure to run the hot water for a good deal of time at several fixtures to flush out any bugs that may have grown in there.