Legionella... Calling Dave Yates

Unknown

Hey Dave... nice seminar at ISH NA!!

I've been thinking about your anti-legionella strategy in plumbing systems. Actually I came up with almost an identical strategy recently minus the scald guard fixtures myself and was very interested to see where you were going.

My question is, if stagnation is a required state for legionella growth, would you consider it adequate protection... keeping in mind that we are not trying to provide sterile environments for our clients, but safe ones... to have a water heater set to 140+, with a tempering valve keeping output temp to 110-120, and recirculation on sinks and showers?

Then the water heater is protected against any possible major blooms of legionella, and the recirc guarantees there is no stagnation in the lines, presumably preventing blooms there as well. Sure a few bugs may scoot through the water heater without dying, but again we're not trying to be sterile, just safe.

any thoughts on this? Thanks again for a very informative seminar and it was really nice meeting you and your family afterwards.

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Dave Yates (PAH)

ISH was a blast!

Thanks. I was very nervous speaking in front of a group - the practice paid off!

In order to offer safety to our consumers, we'll need to make these systems Legionella free or nearly so. While stagnation helps Legionella roam freely about the cabin without the seat-belt sign being lit by the captain, it's just one of the four basic needs. Not all need to be present in order for them to thrive. The 110-120 temps offer temps quite suitable for growth (old folks homes have 110 to 115 F with constant circ & often test positive for Legionella), the pH remains favorable and biofilms offer food and shelter. CIPH has taken a small step in the right direction and your suggestion would move things a bit farther along, but the reality is that we might as well grab this bull by the horns and brand it for what it really is. Until our codes do thast, we'll continue to see more than 100,000 scaldings with hundreds of deaths; and we'll see (CDC estimates) 100,000 LD cases with 10,000 to 15,000 deaths - each and every year.

As Matt Friejie pointed out in his LD class, Legionella often experience sharp rises in numbers as they burst forth from biofilms or cysts of other bugs they've used for a nursery.

The video we did for Watts is now available & it's titled "Scalding - Danger Lurks". It's 25 minutes in length and has much of the same information as was in both of my presentations. In it you'll see video clips, provided by GlobalPipe from Germany, of live Legionella as they burst forth from the cyst of an Amoebae. The GlobalPipe footage is the only film available in the world that shows live legionella in potable hot water systems - a natural habitat for them.

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Unknown

well, I understand the desire to keep things "legionella free" but I think realistically the low level legionella we all live with is not a major problem. The problem is our domestic systems allow for major blooms of the buggy with stagnated lines that feed perfect temperature water and provide ideal breeding grounds.

I also think that going to a "sterile standard" does an overall disservice to people. For instance if you built a home with absolutely perfect air and water quality, you would not develope the resistance to pathogens that are present in everyday life outside the home. I think a small amount of junk in our air and water is a good thing for the vast majority of people. the trick is, in my mind, balancing that against the possibility of dangerous (elevated) conditions of bacterial growth.

Now if you have a tempering valve on the water heater limiting that output to 110 or so, you're pretty scald safe. maybe 105 if you want to be really safe from scalding. The big problem being the perfect temperature is then provided to the hot water lines for legionella growth; not in the water heater itself, but the lines are ripe for it and the few buggies that make it through the water heater could bloom and thrive.

So to what level then does a constant recirc setup, low but continuous flow, back into a water heater hot enough to kill legionella, provide protection?

And using your setup of a tempering valve at 133 out of the water heater, once you account for the drop in temp in the lines itself, is it significantly different? by the time that water gets near the fixtures in a recirc system, it could be 125 or 120, back into happy legionella land, right?

I wonder if a more effective setup could be used with a periodic timed flush that bypasses the tempering valve and circulates high temp water for a half hour a day, say 3 AM to 330 AM or something like that...

It's an interesting situation in any case and you're doing wonderful work raising awareness.. just debating through some possible methods of handling the info you've brought to the table. Keep up the great work Dave!!!

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Dave Yates (PAH)

debate is good

and it makes us think about why or how things work.

The 133 going out into the Distribution Network is the minimum required for a reasonable chance at suppresion and coincides with a number of medical articles that indicate we need to exceed 122 F to begin killing off free roaming Legionella. That's why I'm suggesting the return at the Point of Source be 122 F min.

Part of the problem revolves around the central issue of how many bugs are too many. That number can't presently be determined due to several factors, not the least of which has to do with each individuals health level at the time of exposure. We don't build up immunity to LD through low level exposure, but if we did, we'd all be immune. That is, if we believe the CDC's estimate that 95% of the poulation has been exposed to Legionella.

And you're absolutely right that low level exposure isn't normally a problem. Unless your immune system is compromised, a chronic smoker, alcoholic, aids patient or other illness that makes you more of a host to the bug. And that's where the problem occurs. As our health varies, so does the threat level.

The bottom line is that both scalding and CAP are preventable where man-made potable hot water systems are concerned.

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