Hot water temps-Legionella

Jim Bennett

I have been curious about this myself. I suppose after leaving the tank where the temperature is above the degree where the bacteria can survive, you would be safe. Not being a Microbiologist though, I'm not sure.

Jim

Techman

Hot water -Legionella

Legionella kills and hurts people,so keeping H.W heaters/storages above 140* kills the disease. What happens after(downstream) the anti-scald device? I was on a residential job,1 1/2" manifold with 14 branches,Wisbro Pex, does the Legionella exist in those lines?,or the showerhead? or the faucets?

Jim Pompetti

Water awareness

try this site www.customer.honeywell.com/WaterControl/Cultures/en-US/Prevention/Legionella+in+y

carol_3

An undersink mixing valve solves the problem since it's at the point of delivery.

Singh_3

Extremophiles

I've been reading up on oranisms that live in extreme conditions.
Thermophiles are bugs that live in water at the 140*-176* range.
Hyperthermophiles above 176*.
And other extremophiles that live in high or low Ph levels.

I'm convinced if you manage to kill the Legionella Pneumophila from the water
something else may be lurking.

Also , reading up on the history of Legionellosis pneumonia (Legionnaires' disease) . I find it very interesting that the earliest known cases, besides the 1976 event which it's name orginates from , was in 1965. They have found the bug in 1947(in plumbing systems/HVAC) but was not link to any illness at that time. Most of the victims had recently visited, hotels,hospitals, schools, office buildings, not one of the deaths had occurred from residential home. This also is true for the cases in Europe. I'm sure a lot of misdiagnoses.
Since the bug is naturally found in soil and fresh water supplies, I do beleive there is a threat, and from now on ALL water heaters,indirect tanks will be set at 140* with a mixing valve on each of my installs, no exceptions.
But I'm sure something else down the road is going to get us.
I just find it interesting after WWII when modern plumbing techniques and codes took hold, that Legionnaires also came along for the ride.

JimH

mix valve failure

Hi, I'm preparing to install an indirect DHW system,
and I'm wodering if it's possible for the tempering valve to fail in such a way that no cold is added and scalding
is possible. Is it common practice to add any kind of
redundant safety system?

-JimH

Brad White_9

That is a question

worthy of it's own thread

Rich Kontny_3

I Agree

I agree that there are probaly organisms in all temps of water yet our immune systems usually can handle most of these threats without outbreaks of deadly consequences.

Legionella seems to thrive only in a certain temperature range and in larger volumes of water. It is a problem once formed when it is vaporized and released to the air.Cooling towers and like devices are usually the delivery culprits.

Mark Eatherton can give you a first hand account of how he contracted it after starting up an idle cabin (or second home) tank type water heater that was the perfect environment for breeding these little pests! The mist from his shower was most likely the delivery system.

Frequently used piping is very unlikely to create the proper environment for Legionella.Heating the water to at least 140 degrees takes a great deal of the risk out of any system.

As mentioned above you cannot engineer around all micro organisms that exist. As with anti-biotics they are now finding that it is better for one's immune system to develop the immunity within one's body!

Legionella, however has reached the point of frequency that we have to engineer around it!Hospital and healthcare related facilities most likely already do as I first encountered the temp. requirement on a lab job in 1992.

The small volume on demand water heaters set above 140 and brought down to safe temps near the outlets would lessen the risk also!

Our next challenge coming to a head! Hopefully Mark Eatherton will join this thread as he has first hand knowledge of this potentially deadly disease!

Make Peace Your Passion!

Rich K.

Uni R_4

ASSE 1017 Certified

Mixing valves that are ASSE 1017 certified are supposedly fail-safe.

Dave Yates (GrandPAH)_1

Techman

Great question & one I wrestled with after learning about bacterial amplification in our potable hot water systems. As you noted, we are dealing with a system and not just the water heater. As a result, I came to the conclusion that there are three basic components: Point of Source (the water heater); Distribution System (network of pipes); and Points of Use (where humans come in contact with potable hot water).

While elevating the Point of Source above 140F will suppress the colonies of bacteria and keep them in check, it does not sterilize or eradicate the bugs. That's been a common misconception with Legionella amplification issues. At 140F, there is a required contact time of 20-minutes to kill the free-roaming bugs, so there are plenty of opportunities for bugs to slip on through to the Distribution System and Points of Use. By now, the notion that running 180F water for 15-minutes at each Point of Use will sterilize a potable hot water system should, itself, be dead – but it is persistently promoted as a means to adequately treat a contaminated system. Studies have clearly shown it offers only temporary suppression. Another reason why we need to treat our systems continuously if we’re going to employ hot water pasteurization by elevating the temperature.

The ASSE 1017 certified mixing valves are not technically rated as scald-guard devices. There are combination ASSE 1017/1016 devices, which are classified as scald-guard protective devices. All are designed to fail-safe, which is one of the more important reasons why you should only be using certified devices instead of the less-expensive ones that state they are "in compliance with ASSE 1016 or 1017". The outlet temperature should not be set lower than 133F.

Next we need constant circulation! If we're to protect this Distribution System, we can't let it rest and/or allow temperatures to fall back into perfect amplification ranges. Here's where you'll find more than enough biofilms to support cultures of bacteria.

ASSE 1016 certified scald-guard devices should be installed at all Points of Use. There are three types: P-only (pressure balance); T-only (temperature reacting); and P/T, which react to changes in pressure and temperature. All three are ASSE 1016 devices and our current plumbing codes do not specify which one should be utilized in a given Point of Use. As a result, choice is typically governed by cost. My position: all bathing modules should be required to have the P/T 1016; children’s bathroom sinks the P/T or T; and the other areas like kit sink or laundry tub could have the P. Bear in mind that P-only models are blind to seasonal temperature changes in municipal water supply lines, which often vary by as much as 50F from winter to summer. As a result, what you set as an upper limit today will not be accurate six months later and will allow delivery temperatures to be unsafe.

One thing more to consider: how far away from a Point of Use should an ASSE 1016 device be and still consider the distribution line(s) adequately protected? No one is certain. Distal sites (shower heads, etc.) will still be able to amplify, so it’s important to decide what distance will be allowed from the 1016 device to the faucet (if the faucet is not itself an ASSE 1016 device) and what distance will be permitted from the recirc loop to the 1016 mixing device. I’m convinced water-volume plays a role here, which would mean different distances for varying sizes of water lines. I’d personally like to see no more than ½-gallon of water dispelled ahead of the protected water stream.

You might find the Watts DVD “Scalding – Danger Lurks” of interest. It’s free for the asking by visiting wattsreg.com and following the video link.

Unknown

Thermostatic mixing valves

Thermostatic mixing valves are supposed to fail in the no flow position but any product can fail and failures do happen.

I am reminded of the case in lower NY where a handicapped woman was put in a hydrotherapy tub that had been filled with 125°F water. She was literally cooked to death.

The mixing valve, which I had sold, had failed after three years with no maintenance. All commercial mixing valves have a tag affixed which clearly states the need to maintain the valves with regular cleaning.

I don't think that there is much chance of serious scalding with a residential valve set to deliver tempered water but it certainly is a good idea to manually move the handle on the valve occasionally to free up the mechanism.

The killer with all similar valves is sediment and any sort of build-up that might freeze the valve.