Legionella & Water Heaters-Seattle Times

Doug_7

Oregon OSHA Technical Manual - Legionnaires

The Oregon OSHA Technical Manual Chapter 7 pages 160 and 161 provides some useful information on Legionella in Domestic Hot Water Systems. Chapter 7 on Legionnaires disease is 33 pages.

Main point on Design and Maintenance is that DHW storage temp should be a minimum of 60 C / 140 F and delivery temp should be a minimum of 50 C / 122 F. Eliminate dead legs and also sludge and scale needs to be periodically removed from the tank.

Interesting comment that point-of-use water heaters are good because they eliminate stagnation.

Also a good point that DHW piping should be insulated and recirculation systems should run continuously to maintain temperatures.

These are your Safety and Health people.

Doug

Alexia

I also notice the mention of rubber seals. The only places that come to mind in my home are the water meter fittings and shower head gasket, though the shower head itself is all brass. My faucet aerators all have plastic internals and the faucets are likely rubber seal type, maybe ceramic. I don't know where ceramic plays in the legionella equasion.

Oh, there is the plastic impeller and rubber seal in the Taco circ pump too. Seems a bit mission impossible.

zeke

It seems to me that Alexia's solution meets all the criteria for a reasonablly safe system, given that all of the utility water will pass thru the baseboard elements in the summer, which equates to your standard hotwater system taking a longer path enroute to the hotwater heater. There is no more risk there than in your standard hotwater system, the only problem being condensation on the heating loop during heqvy hotwater usage and high house humidity which is not a health issue.

Alexia, just keep the hotwater in the tank at or greater than 152 deg. for maximum safety.

Alexia

Absent a safe and effective chemical sanitation system temperature does seem the best approach. I definately want to keep my system safe and I'm very glad I saw this thread. I have learned a lot.

Still keeping my fingers crossed that the system doesn't turn into a condensation problem on the baseboard pipe. I'll probably stick with the tank for a minimum of this year. If all goes well I'll look into a small natural draft tankless. This topic has made me dislike my tank.

Unknown

Good info

from Watts on Leginaires. WWW.Watts.com

[Deleted User]

the only problem being condensation on the heating loop during

heqvy hotwater usage and high house humidity which is not a health issue.

You obviously have no allergies to molds....

I don't believe ANYONE has ALL the solutions to ALL the potential problems associated with these water borne diseases, but if one is aware, and can take actions to avoid un-necessary exposure, then that is a good thing.

Eventually, a good long term solution will be found and we can all use cheap inefficient water heaters as our heat sources... (been there, done that, replaced with a real boiler and reduced my energy consumption significantly)



ME

Paul Pollets

The Seattle Solution

I spent Wed. eve with John Barba from Taco. We discussed the open system problems and see that the Taco RMB (radiant mixing block with HX) would close off the system side, and still allow the use of a water heater. It would also add an outdoor reset strategy to the equation.

I'm sure we'll hear the argument that "it costs too much".

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