Electric hot water heater / Legionella bacteria concerns

[sv_pelagia]

Originally Posted by StuM

Obviously written by someone who lives in a cold/temerate climate
I haven't seen tap water or an ambient termperatre that low for years.

Tap water in BC (and our boat tanks) currently well below 20°C... [emoji6]

[sailorboy1]

Originally Posted by GordMay

It's not that Legionella likes plastic, it's that shower heads aerosolise the bacteria, so they can be inhaled.

Yes. But what I said is that Legionella acturally like to grow in plastic!!! This what my last water treatment company found when we decided to start a division just to treat Legionella. The bacteria likes to grow on plastic and just flushing the water lines wasn't enough. So shower heads and later we found the same in water makers in hospitals. Of course shower heads are the worst as it grows in it and then sprays to be breathed in.

BTW hot water systems are acturally worst than cold cold it likes 90-120 degrees. So in those hot water lines once it cools down it ..................

I'm not posting about this anymore as this is boating forum and it has been covered in more than enough detail for boating.

[s/v Jedi]

Originally Posted by zstine

not in the USA. our heater home heaters are set at about 130F. if the water is chlorinated, there is virtually no risk of Legionella.

We’re talking boats here. My Isotemp is old and from before they were required to come with the thermostatic mixing valves, but due to legionnaires risk they changed that.
https://www.defender.com/expanded.js...311&id=2355999

[belizesailor]

Ive never heard of an issue with legionellas aboard any cruising boat. Does anyone know of any cases?

[rslifkin]

I've debated adding the thermostatic valve to my water heater, but having always lived in houses with very hot water, I've just gone with "don't set the shower to full hot and don't use full hot if your hand is in the sink". If I remember, when I commission in the spring I'll check my hot water temp.

[GreenWave]

Originally Posted by Brewgyver

And, PLEASE!!!

It's called a water heater, be it electric or gas fired. NOT a "hot water heater."

This is worth pointing out? Porbably as good as me pointing out that the post was a waste of time. :-)




You were being sarcastic right?

[GreenWave]

Originally Posted by Exile

Thanks for confirming the comments from the surveyor. I'll look for these pan tablets you mentioned. Sounds easier than pouring bleach into the bilge (I don't have condensate pans and the a/c's are plumbed to drain into the bilge). I recently installed a new bilge pump with a remote pickup which at least gets the water level down to less than an inch. Has made a big difference in musty odors in the cabin but I imagine even a small amount of (sufficiently warm) water is enough to breed the nasty stuff.

I bought some of these tabs on Amazon. readily available for not much $$$.

[belizesailor]

Originally Posted by Brewgyver

And, PLEASE!!!



It's called a water heater, be it electric or gas fired. NOT a "hot water heater."

Its an American thing!

[belizesailor]

Originally Posted by s/v Jedi

We’re talking boats here. My Isotemp is old and from before they were required to come with the thermostatic mixing valves, but due to legionnaires risk they changed that.

https://www.defender.com/expanded.js...311&id=2355999

+1 IsoTherm. Good product. Mine has a mixing valve which is clever too because its effectively like having a much bigger tank by mixing right at the tank outlet.

Of course, in theory, that probably means the water in the pipes is exactly the right temp range for bugs to grow, but we have never had any issues. I santize the entire system at the start of each season either with chlorine or propolyne glycol (if Ive got it).

[s/v Jedi]

Originally Posted by belizesailor

+1 IsoTherm. Good product. Mine has a mixing valve which is clever too because its effectively like having a much bigger tank by mixing right at the tank outlet.

Of course, in theory, that probably means the water in the pipes is exactly the right temp range for bugs to grow, but we have never had any issues. I santize the entire system at the start of each season either with chlorine or propolyne glycol (if Ive got it).

When water lines have been stagnant for a longer period, that could possibly be a problem. Key is to flush in a safe manner after a period of non-use, i.e. not by shower head, good by flushing fresh water toilet.

[Chotu]

Hmmm. The informative post gord made earlier about the temperatures and fumes required to both grow and kill the bacteria says my water tank is too warm AND I don’t leave the hot water heater on long enough to kill the bacteria.

Even if I did leave it on fir an hour at 150, according to Gord’s post, it wouldn’t matter since the cold water I’m mixing with the hot while showering is a perfect breeding ground for it.

So making sure my chlorination of the fresh water tank is robust (same word/logic pattern as hot water heater by the way)is the only way to head off this bacteria?

Further, this means tankless hot water heaters can’t kill legionella since they don’t keep the water hit for a long enough time period.

None of this makes logical sense.

[Franziska]

That's why I am considering two options mentioned further above.
Proper hot water on demand heater, even though less common on boats, run it few seconds very hot and than adjust to shower temperature.

If using a typical boat calorfier with a buffer tank and no inboard engine, heat the water up very hot initially by genset, and to maintain heat run a thermosolar loop through the heating coil which is normally used for the cooling water">engine cooling water connection.
Possibly that could work in hot & sunny environments? At night the pump motor shuts off if it doesn't have sunlight.

I guess adding some silver iodine & bleach is not wrong in any case.
Maybe add a carbon pre-filter just before the shower head as well?

Just my 50cent.

Originally Posted by Chotu

Hmmm. The informative post gord made earlier about the temperatures and fumes required to both grow and kill the bacteria says my water tank is too warm AND I don’t leave the hot water heater on long enough to kill the bacteria.

Even if I did leave it on fir an hour at 150, according to Gord’s post, it wouldn’t matter since the cold water I’m mixing with the hot while showering is a perfect breeding ground for it.

So making sure my chlorination of the fresh water tank is robust (same word/logic pattern as hot water heater by the way)is the only way to head off this bacteria?

Further, this means tankless hot water heaters can’t kill legionella since they don’t keep the water hit for a long enough time period.

None of this makes logical sense.

[Chotu]

Originally Posted by Franziska

That's why I am considering two options mentioned further above.
Proper hot water on demand heater, even though less common on boats, run it few seconds very hot and than adjust to shower temperature.

If using a typical boat calorfier with a buffer tank and no inboard engine, heat the water up very hot initially by genset, and to maintain heat run a thermosolar loop through the heating coil which is normally used for the engine cooling water connection.
Possibly that could work in hot & sunny environments? At night the pump motor shuts off if it doesn't have sunlight.

I guess adding some silver iodine & bleach is not wrong in any case.
Maybe add a carbon pre-filter just before the shower head as well?

Just my 50cent.

But according to Gord’s post, the on demand heater cannot work at all.

It says 2 minutes is the minimum time to kill the bacteria at the highest temperature. An on demand hot water heater only heats the water for seconds.

I have already bought an on demand heater for my boat.



Then there is the fact that no water tank is below 68F (20C) in the tropics. According to his post, the cold water is also a risk.

So that seems to leave chemical defense as the only option. Yes?

Note: I have no cooling loops. Outboard engines only.

Edit: whoops. Thermosolar. Missed that. Sorry.

[Franziska]

An unconventional thought and out of the box idea:

Add some sort of water loop for the water from the in demand heater. Run this 2 minutes through the shower head and heater and back.
Then switch it to the freshwater tank, that could kill at least the growth in the water heater and shower head.

But, as I have not heard of boaters with issues we may overthink this one, it seems not to be a real issue on boats (not sure why).

Anyway, agree, chemicals and than a carbon filter to remove them right before they exit the shower head might be the closest workable solution.
Possibly combined with proper filtering of shoreside water before it goes into the tank.
Needless to say, run shoreside hose few minutes before filling...

Originally Posted by Chotu

But according to Gord’s post, the on demand heater cannot work at all.

It says 2 minutes is the minimum time to kill the bacteria at the highest temperature. An on demand hot water heater only heats the water for seconds.

I have already bought an on demand heater for my boat.



Then there is the fact that no water tank is below 68F (20C) in the tropics. According to his post, the cold water is also a risk.

So that seems to leave chemical defense as the only option. Yes?

Note: I have no cooling loops. Outboard engines only.

Edit: whoops. Thermosolar. Missed that. Sorry.

[GordMay]

Originally Posted by sv_pelagia

... One thing the literature is clear on, is that chlorine is not very effective in killing giardia (neither is iodine). A higher concentration and longer contact time is required. Chlorine dioxide is better, but still needs a long contact time (4 hrs...). Neither deal with Cryptosporidium.

Good/fine filters (0.2 u) can screen out relatively large giardia, other protozoa, as well as most bacteria. UV Light takes care of giardia and other protozoa, as well as viruses. There are combo filter/UV units suitable for boats (even 12V): for example, https://waterfixercompany.com/index.html

There are three main types of disease-causing micro-organisms that affect drinking water: bacteria, viruses and protozoa, such as Giardia, and Cryptosporidium.
Giardia and Cryptosporidium:
Drinking water is disinfected to destroy, or inactivate, the micro-organisms that are not filtered out.
Chlorine is the most common disinfectant in the world. It can work against Giardia*, but not Cryptosporidium.
Ultraviolet (UV) light is another type of disinfectant, that works against, both, Giardia and Cryptosporidium.
Since protozoa are relatively large micro-organisms, they are easier to filter out, than bacteria and viruses.

Look for a filter that has a (absolute, not nominal) pore size of 1 micron or less. The protozoa removal standards (NSF/ANSI Standard 53 or Standard 58) are set by NSF International (NSF), or the American National Standards Institute (ANSI).

* Protozoan cysts such as Entamoeba histolytica and Giardia lamblia are highly resistant to chlorine disinfection and may require prolonged contact times at high chlorine residuals (2–3 mg/l) to achieve 99.9% (3-log) inactivation.
The United States Environmental Protection Agency (USEPA) has published extensive CT tables for Giardia inactivation, for different temperature, pH, chlorine residual and other factors (USEPA, 1989b). For example, at a temperature of 25°C and pH 8.0, with a chlorine residual in the range of 1 to 2.6 mg/l, a contact time of 54–65 minutes is needed to achieve a 3-log reduction in Giardia. If the temperature is reduced to 10°C, the contact time increases to 162–194 minutes, and at 0.5°C it increases further, to 304– 368 minutes.
Certain bacteria show a high level of resistance to free chlorine. Spore-forming bacteria such as Bacillus or Clostridium are highly resistant when disseminated as spores. Acid-fast and partially acid-fast bacteria such as Mycobacterium and Nocardia can also be highly resistant to chlorine disinfection. One study showed that nearly all of the bacteria surviving chlorine disinfection were Gram positive or acid fast (Norton & LeChevallier, 2000), possibly because Gram-positive bacteria have thicker walls than Gram-negative ones.
Chlorine-based disinfectants are generally not effective at inactivation of Cryptosporidium and early studies found that Cryptosporidiumoocysts were resistant to a variety of hospital disinfectants, including bleach.

Additionally, water ph, turbidity, and temperature can affect the efficacy of bleach, as a disinfectant.

Accordingly, I’ll withdraw my recommendation of chlorine bleach, as a disinfectant for Giardia. Bleach many not be suitable/effective, as commonly practiced.

WHO Water Quality Standards: Inactivation (disinfection) processes
➥ https://www.who.int/water_sanitation...treatpath3.pdf

“Affect of Chlorine on Giardia lamblia Cyst Viability” ~ by Edward L. Jarroll ety al
➥ https://www.ncbi.nlm.nih.gov/pmc/art...00195-0159.pdf