Electric hot water heater / Legionella bacteria concerns

[Franziska]

Thanks guys, valuable input.

[GordMay]

Originally Posted by rslifkin

If you're willing to run a few pre filters, you can handle most types of contamination. Something along the lines of a fine sediment filter, then a carbon block filter, then something like GAC+KDF, then an oil/hydrocarbon removal filter [2]. Of course, all the extra filters starts to get expensive, especially the more specialized ones. So I wouldn't bother with it unless you really needed to.

Indeed.
Activated Granular Activated Carbon [coconut shell] , GAC, is used, in combination with KDF* media, to significantly extend the life of filtre cartridges.
KDF-55 media is a redox media, that removes chlorine, and reduces heavy metals.
KDF-85 removes hydrogen sulfide, and reduces iron, by the redox process and filtration. Both KDF®* redox media are bacteriostatic, and inhibit the growth of microorganisms in the filter.
* Patented by KDF Fluid Treatment, Inc.

➥ https://www.home-water-purifiers-and...ter-filter.php


[2] Are you aware of a flow-through oil/petroleum filtre, suitable for use on a typical cruising boat? I'm not.

[rslifkin]

Originally Posted by GordMay

[2] Are you aware of a flow-through oil/petroleum filtre, suitable for use on a typical cruising boat? I'm not.

Pentek lists their OAC-20BB (only comes in the one giant size) as removing glycol and hydrocarbons. There are also those filters meant for removing oil from bilge water discharge, so the stuff is definitely out there.

[GordMay]

Originally Posted by rslifkin

Pentek lists their OAC-20BB (only comes in the one giant size) as removing glycol and hydrocarbons. There are also those filters meant for removing oil from bilge water discharge, so the stuff is definitely out there.

I'd be pleased to be exposed as ignorant, but the Pentek OAC-20BB won’t provide adequate pre-filtering, for an R/O watermaker:

ONLY Up to 90% of total hydrocarbons are removed in a single pass
BIG For use in 20 inch Big Blue® filter housings
LOW Flow Rate 5-10 gpm (19-38 L/min)
➥ https://www.thewaterguy.ca/catalog/v...8aAj7LEALw_wcB

[Buzzman]

Originally Posted by Franziska

That's a different game. Home water cylinders are permanently attached to electricity and the heater kicks in when the water gets below a certain heat.

Not necessarily.....

In Oz, we have an electrically heated HWS power supply colloquially called 'off peak hot water supply'.

Essentially, many years go, it was noticed that there was little demand for electricity over night, and so the generators had to run down, which was not good for them, so the 'authorities' came up with a plan to utilise the excess power being produced by the idling generators at night.

'Peak power' was when lots of demand was on the grid, 'off peak' when demand was low. So to better utlise the 'off peak' supply, they enabled a system whereby water heaters ran ONLY at night. This supply is separate to the 'main' supply, and can only be utilised by the water heater, which is the only appliance legally allowed to be connected to it. The carrot was that such 'off-peak' power was one third the price of the regular 'mains peak' supply cost.

So each house was fitted with a 'ripple switch' - which detected a radio signal sent along the power lines by the power distributor, that then 'switched on' the "off peak hot water supply".

Now these ripple switches were only able to activate after 11.00pm and usually switched off before 7.00am.

The element in the heater tank was also thermostatically controlled, so would turn itself off once water in the tank reached a set temperature. So an insulated tank might only switch on and run up to temp once per night.

This temperature was usually set at 60 deg C, as this was the optimum temp for killing Legionella but not scalding users.

In very recent times it has been mandated that such water heaters be now fitted with a compulsory tempering valve, to mix the 60 deg C water from the tank with cold water supply to reduce faucet/tap temperature to 45 deg C, as this is considered a 'non-scalding' temperature and is thus safer for babies, the elderly, and the idiots who jump into a hot bath and scald themselves. But the temp in the tank will still kill the Legionella.

The POINT is that once the tank reaches 60 deg C it cuts power to the element, so probably is only at 60 deg C for an hour or too, enough to kill the Legionella, apparently, and perhaps only once a night at best.

My conclusion from this practice - that demonstrably does not lead to legionella outbreaks - is that an occasional burst to 60 deg C is probably sufficient on a boat.

It is also my understanding (mate who works for Zip instant-boiler maker) that instantaneous hot water heaters are designed to kill Legionella, so even though of shorter duration (water heated to req temp for less time) it is done to an 'adequate' level.

I conclude there is nothing to worry about if you have a heater on the boat, *provided* it is cycled occasionally to kill any outbreaks that might have somehow survived the last heating cycle.

Another point: that article on copper silver filtration linked to by Franziska is quite clear that carbon-activated filters are a *known* breeding ground for such parasites and clearly therefore require regular cleaning and or flushing to remove the biofilms that support the microbes. They actually stated that up to a month after the 'testing' process Legionella were still apparent in pretty regular concentrations in the effluent from the filters.

They concluded that, while it appeared from the results that combining the carbon and silver seemed to lead to a reduction in Legionella bypassing the filter, compared to the non-silver carbon filtration, that it was not a 100% removal, so could not conclude that using such a combo was advisable.

Ergo, reliance on any sort of carbon-filtration system might be risky, if Legionella, giardia or cryptosporidium were the targets. Fine for removing chlorine (what kills everything else) and other 'odours' but not so great for removing organisms.

Heat to 60 deg C kills the Legionella; mechanical filtration below 0.5 microns takes out the others.

[jmh2002]

Yes, my home in France had a similar setup with the electric hot water heater.

It had a special breaker at the circuit board which could be set to Off / Auto / Manual.

Auto would run the hot water heater only during off peak electricity times, so in general that meant only at night.

As you said, this was to utilise the off peak power generation excess, which was also cheaper per kW too.

(it was also common for dishwashers, washing machines, etc, to have programmable timers, and it was encouraged to run these at night as well).

This all worked on the logic that most people had a shower when they got up in the morning before going to work so that's when most of the water needed to be hot.

And it did mean that it in Auto the hot water would only be heated to maximum temperature once per day.

[GordMay]

Originally Posted by Buzzman

... My conclusion from this practice - that demonstrably does not lead to legionella outbreaks - is that an occasional burst to 60 deg C is probably sufficient on a boat.
It is also my understanding (mate who works for Zip instant-boiler maker) that instantaneous hot water heaters are designed to kill Legionella, so even though of shorter duration (water heated to req temp for less time) it is done to an 'adequate' level.
I conclude there is nothing to worry about if you have a heater on the boat, *provided* it is cycled occasionally to kill any outbreaks that might have somehow survived the last heating cycle ...

On-demand, instant, water heaters don’t necessarily kill Legionella, but neither do they store water, allowing time for the bacterium to grow to toxic/ virulent numbers - hence are “safe”. Neither do conventional water heaters.
The danger lies (mostly) in stored water.

As previously noted:
"Legionella, the bacterium that causes Legionnaires’ disease, occurs naturally in freshwater environments, like lakes and streams. Generally the low amounts of these bacteria in freshwater do not lead to disease. However, Legionella can pose a health risk when it gets into water storage systems.
To do this, Legionella first has to grow (increase in numbers). Then it has to spread through small water droplets (aerosolization) that people can breathe in.
After Legionella grows, and multiplies, in a water system, water containing Legionella then has to spread in droplets small enough for people to breathe in. People can get Legionnaires’ disease or Pontiac fever when they breathe in small droplets of water in the air that contain the bacteria.
Less commonly, people can get sick by aspiration of drinking water containing Legionella. This happens when water accidently goes into the lungs while drinking.
So, treated water (chlorinated muni', or R/O) is highly unlikely to contain Legionella, and our storage tanks aren't likely large enough to retain water long enough to grow significant numbers of bacterium, to cause illness."
Here ➥ https://www.cruisersforum.com/forums...ml#post3315052

Also ➥ https://www.cruisersforum.com/forums...ml#post3315062