UV lamp before the water faucet : when should it be turned on ?

[JstaRebel]

Originally Posted by Brann-

Regarding the lifespan issue, unfortunately, I've been unable to find any actual figures so far. I have no idea how long it would take an UV lamp to drop below the 70% efficiency threshold if used say once a day every day. This information is definitely the key in my opinion

With regards to bleach, I heard from an engineer specialized in water treatment that it could react with the metal contained in the water to create harmful compounds. I have no idea whether this compounds can be efficiently filtered or not. I know bleach is a very popular solution, but it doesn't mean it's a good one.

I'm a licensed​ engineer specializing in desalination and water treatment. We make water for most islands in the Caribbean. .5ppm bleach is all that is needed for sanitization. That's a very small amount. Maybe a cap full for 100gallons.. like I said, I didn't figure my post would be popular. But it is relevant to the discussion. People need to do what makes them feel safe. Sometimes it's not correct, and sometimes it is.

[JstaRebel]

Originally Posted by bcboomer

Brann.

No, I meant 12 volt lamp.
I'm a little confused.
The OP is talking about water from his watermaker, shouldn't be any metal in the water.
Why would one include a charcoal filter in this system?
Why would one want the expense and bother of a UV lamp for RO water?
Where would viruses come from in this system?
I am looking at putting in a watermaker and thought that the produced water would be clean enough to drink as is.

It is clean enough to drink as is. The post carbon filter will make the water taste better , but nothing is actually necessary if you don't want. A UV system after a watermaker is a complete waste of money and power.

[noelex 77]

Originally Posted by senormechanico

When cruising, we just use our Spectra and our immune systems.

Great line.

We have used our Spectra water (no bottled water) with no treatment or extra filtration for the last 7 years with not a single tummy upset.

[toddster8]

I test water for people day in and day out.

With very, very few exceptions, every single home treatment system with a UV component that I have tested has more bacteria coming out of it than going into it. I have not examined any of these systems in person, so I don't know whether this is due to poor installation, poor equipment, or poor operation.

Every fancy filter that you can buy that screams how many bacteria it removes is worthless. They work for about 1 - 6 hours, just enough time to pass a "test" for advertising purposes. Thereafter, they become excellent habitat for bacteria, and a net source of microorganisms. The ones that really work in laboratory and industrial settings require high pressure and daily maintenance, or they're single-use things that are only good for a few milliliters.

For most people, this isn't much of a problem, other than wasted money, since most bacteria are harmless. Only people with a compromised immune system, or a requirement for ASTM Type 1 laboratory water really need to worry about this. The trick is avoiding septic contamination of the water source to begin with. That is, contamination from an animal source and hence potentially disease-causing microbes. The animal source closest to your water supply is you. Your microbes won't make you sick, but a shared water system is a potential disease-transmission pathway.

Even the best distribution system needs an occasional shock-chlorination.

Occasionally, people have shipped water samples to me from their vacation homes in Mexico or various islands. Most of these were not shipped quickly enough for a really valid test, but the only remarkable thing about these samples was that most Mexican samples seem to have a lot more residual chlorine than US municipal sources.

Personally, I don't spend money on treatment systems (except for my laboratory.) Annual testing, annual shock chlorination, and when filling tanks from unknown sources, add the recommended amount of chlorine bleach. Some day I may save up enough nickels for a water maker on the boat, but I wouldn't add any additional treatment downstream from that.

[Snore]

Toddster

I have a significant background in running a potable water distribution system and maintaining water quality. You are right, keeping it clean with a CL residual is key.

That said, I always thought that the role of UV was to "inactivate" the bacteria. In other words they were still alive, but could not multiply and cause illness.

Did the Bac-T testing you do test for presence or did you also monitor for growth?

Not looking to argue, just learn.

[JstaRebel]

Originally Posted by Snore

Toddster

I have a significant background in running a potable water distribution system and maintaining water quality. You are right, keeping it clean with a CL residual is key.

That said, I always thought that the role of UV was to "inactivate" the bacteria. In other words they were still alive, but could not multiply and cause illness.

Did the Bac-T testing you do test for presence or did you also monitor for growth?

Not looking to argue, just learn.

Ultraviolet purification systems were first designed to be installed on high purity water loops on industrial applications such a pharm manufacturing as well as food and beverage manufacturers. Following these lights were 0.4 Micron absolute filters for removal of the endotoxins. I don't know how they came to be used in residential water treatment especially as point of use systems. They use to be used in dialysis water treatment too, but were found to be more of a liability regarding patient care and were replaced by absolute micron depth filters and membranes.

[toddster8]

Originally Posted by Snore

Toddster

I have a significant background in running a potable water distribution system and maintaining water quality. You are right, keeping it clean with a CL residual is key.

That said, I always thought that the role of UV was to "inactivate" the bacteria. In other words they were still alive, but could not multiply and cause illness.

Did the Bac-T testing you do test for presence or did you also monitor for growth?

Not looking to argue, just learn.

These were all growth-based tests. Usually heterotrophic plate counts and coliform/E coli differential membrane filters.

Here's an attempt to cram a half-hour lecture from Sophomore Microbiology into a paragraph. As you mentioned, antibacterial treatments can be bactericidal (kill bacteria) or bacteriostatic (prevent growth but not kill). Sometimes, the difference is just a matter of exposure time and intensity. Bactericidal killing is a stochastic process. For a given intensity of treatment, a certain percentage of the population is killed per unit of time. For sterilization, the treatment has to be continued for enough time that the probability of survival is less than one cell per unit volume.

UV causes physical damage to the cells, so I think it falls into the bactericidal category, but at low doses, it is repairable damage. A typical response for an incompletely sterilized sample is that colonies that would ordinarily appear on a culture plate (each from a single cell) after 24 hours might not appear until 72 hours, and then might be very tiny for the first day or so. Similar to what you get with heat shock. In that case, if you consumed and excreted the water in 72 hours, your immune system might bet the better of the damaged cells. However, that is NOT the growth pattern that I usually see from "UV treated" customer samples. (I do see it occasionally.)

[thinwater]

Originally Posted by Brann-

Unfortunately, while a 0.05 filter will certainly help, it won't stop viruses below the 50 nanometer limit, of which there's plenty of examples (see this link for typical viruses size : » How big are viruses? )

If you want to be protected against these, the only efficient option I know of is UV filtering.

True enough on the Microguard, bu the DVG-50 is NSF P231 rated, which includes viruses. That is the highest rating there is. Not all UV systems meet NSF-P231, and very few systems that do not include multiple steps. If you are very concerned, then chlorine + filtration is probably the best bet. Practically any one-step systems has weaknesses.

[thinwater]

Originally Posted by YachtBroker

In-Home Water Purifiers and Micro Water Filters - General Ecology

their seagull filter will filter out mexican tap water. Never buy bottled water again and drink the water right out of the tanks without any tank taste.
Filters last at least a year.

Been using these and equipping boats with the Seagull for years.

Curiously, Seagull is not NSF rated. I believe it would probably pass. But it is quite pricey compared to the rated filters I listed.

[davil]

Bran
we cruised for 4 years,most times made our water with our PUR,have about the same setup as yours,and included the UV lamp right at the end of the system and before the faucet,in fact installed right under the sink.
Decided the safer,safe and easier way for my needs was to use an electric switch to power the lamp before opening the faucet.
I used only this system for drinking or cooking,water.
I felt did not have to treat the water for cleaning dishes as I used soap and chlorine.
Happy cruising
David

[redsky49]

Does one of your crew have an immune system issue or other health concern?

On the other hand, are you comfortable with drinking water from a municipal water system?

The quality level you are seeking is far above typical drinking water standards. If there is reason for such demanding standards, UV may not be the best choice.

My experience with ultra high quality laboratory water is that it requires specialized systems (glass piping, for example) that are incompatible with life at sea.

The 0.5 micron NSF 53 system mentioned by Thinwater is indeed a very aggressive filtration system, requires no electrical source, virtually maintenance free and is affordable. It is a practical solution. I use a similar approach on board my boat.

If you are dealing with extraordinary health issues, I could suggest some additional steps. Otherwise, the above will provide excellent protection.

By the way, what are the cruising areas you anticipate?

[Johnno]

That's why God invented beer, so we wouldn't have to drink water ever again!

[Valmika]

Originally Posted by toddster8

I test water for people day in and day out.



Occasionally, people have shipped water samples to me from their vacation homes in Mexico or various islands. Most of these were not shipped quickly enough for a really valid test, but the only remarkable thing about these samples was that most Mexican samples seem to have a lot more residual chlorine than US municipal sources.

Personally, I don't spend money on treatment systems (except for my laboratory.) Annual testing, annual shock chlorination, and when filling tanks from unknown sources, add the recommended amount of chlorine bleach. Some day I may save up enough nickels for a water maker on the boat, but I wouldn't add any additional treatment downstream from that.

So would you recommend pool chlorine over laundry chlorine and what ratios for both maintenance and shock

[toddster8]

I don't add any bleach for good municipal water (e.g. my home dock) it's usually already got a chlorine residual.

For water of unknown quality, WHO recommendation for clear water is "8 drops" household bleach per gallon. Works out to four teaspoons for my 30 gallons. They recommend twice that much for "cloudy water," but let's hope we don't have to go there.

I use the cheapest generic brand household bleach that comes in a convenient small bottle - no perfume or any other kind of additive.

I only consider swimming-pool stuff when shock chlorinating a large volume - like a whole well and distribution system.

[Brann-]

Originally Posted by J Clark H356

Brann: The UV light with the SafeH2O system comes on when I energize the circuit breaker for the water pump and stays on until I leave the boat

ok I see, this makes sense ! The only issue I see is that you could have bacteria growth in the UV chamber when the system is off, which will opacify the lamp. Turning it on OK will kill this bacteria allright, but won't make them transparent. Unless maybe you clean thoroughly the lamp before turning it on when you come back on your boat ?

Originally Posted by davil

Decided the safer,safe and easier way for my needs was to use an electric switch to power the lamp before opening the faucet.

But how do you deal with the issues mentionned in the original post then ?

Originally Posted by toddster8

I test water for people day in and day out.

With very, very few exceptions, every single home treatment system with a UV component that I have tested has more bacteria coming out of it than going into it.

Wow, that's very eye-opening !
One area where UV lamps are used extensively is to clean pond water. Usually, they seem to be quite good at turning turbid water into crystal clear water. I agree having clear water isn't the same as having bacteria-free water, but surely it's somehow correlated, and seem to prove that those UV filters work at least to some extent ?

Originally Posted by thinwater

True enough on the Microguard, bu the DVG-50 is NSF P231 rated, which includes viruses.

Oh ok, I overlooked this. I didn't find the size information anywhere and assumed it was yet another 5 microns filter. I'll take a closer look then ! Thanks

Originally Posted by redsky49

Does one of your crew have an immune system issue or other health concern?

We're having a baby, so we want to be extra careful. I guess there's always the possiblity of using bottled water, but we don't like the idea (and the sheer mass of plastic waste it generates)

Also, my wife is an emergency doctor, so probably a bit on the paranoid side of things with regards to health issues. See saw first hands what can happen if you drink contaminated water.

Originally Posted by redsky49

By the way, what are the cruising areas you anticipate?

We're in Marseille, France right now, but as soon as the baby is there we'll be off to the Canary Islands, then across the Atlantic .. After that, we haven't decided yet, maybe due south towards Patagonia, or maybe directly the Pacific Ocean through Panama ... Anyway that's the plan for now