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

[Brann-]

Hi,
I'm looking for advice on the topic of UV sterilization on a boat.


My current setup is as follows :
- one tank that I can easily open and clean dedicated to drinkable water. Its water comes straight from the watermaker
- a pressure pump connected to this tank
- a solenoid control valve
- two filters (charcoal, 5 microns)
- one remineralization filter
- and finally the faucet

I'm considering adding an UV filter right between the two groups of filter (after the charcoal and 5 microns filter so that the water that passes through the UV lamp is crystal clear, and before the remineralization filter for the same reason)

I'm wondering how I should manage the power cycle of my UV lamp, which consumes 25W and is rated for 9000hours.

One one hand, having it powered-up 24/7 is an easy solution, but it will eat up 50Ah a day, everyday, which I can't afford.

One the other hand, turning it on only when I need tap water isn't feasible either. Those lamps need a few minutes to power-up, excessive power cycling seem to reduce the UV lamp lifespan, and I've also read that the UV filter being off can lead to bacteria growth on the quartz, which will then block UV and prevent the lamp from doing its job.

I can also turn it on every day, fill a 2gal jerrican, turn it off for the rest of the day. and use the jerrican when I need drinkable water.

the problem I don't have is forgetting to turn on the UV lamp before I use the faucet, as I can easily wire a relay on the solenoid control valve to prevent it from opening if the UV circuit is off.

The middle of the road solution seems reasonable, but I'm curious to know how others have addressed the issue ; I'm also interested in actual figures regarding how lamp lifespan correlates to on-off cycling frequency.

Thanks a lot !

[thinwater]

...Which is why most people ditch UV and go with either an NSF 53 rated carbon block filter (0.5 micron) or something like a Pentek Microguard (0.05 micron). There is also the Pentek DVG-50, which is NSF P-231 rated as a microbilogical barrier. These are quite defective and don't use power.

(it's listed toward the bottom on this post)
Sail Delmarva: Drinking Water Filtration--The Short Version

Another thing to remember about water filtration is the law of diminishing returns. You are going to be swimming, eating, drinking and shaking hands locally.

[J Clark H356]

I have SafeH20 system. I replace the lamp yearly as well as the filters after recommissioning my system using Peggy Hall's method. My UV filter comes on with my water pump circuit breaker and runs continuously while the breaker is on. We have great water. My annual costs for filters and UV lamp is $53.

[Brann-]

Originally Posted by J Clark H356

My UV filter comes on with my water pump circuit breaker and runs continuously while the breaker is on. We have great water.

Thanks for sharing your experience.

If I'm not mistaken, it seems you do two things that I would have thought to be a problem :
- you start circulating water through your UV lamp right off the bat, without letting it the time to warm up. To my knowledge, UV lamp efficiency is linked to their temperature, hence the need for a warm up period.
- you turn your UV lamp on and off very often (every time you need tap water!). This causes changes in temperature very detrimental to lamp longevity. Also, starting the lamp emits some tungsten particles that end up blocking the UV emitted by the lamp, which is obviously bad.

See this link explaining those issues : http://www.freshaireuv.com/info/asse...light-2002.pdf

After the first 100 hours of use, UV lamps efficiency decrease vastly. The typical 9000h (or one year) rating you see on bulbs is the time after which the lamp has reached less than 70% of its initial efficiency provided it's always on. I have no idea whether a lamp that has only 100 hours of use but a thousand on-off cycle behind it is in better shape than the canonical lamp with 9000h of use but no cycling at all.

To make things worse, to my knowledge, there's no easy way to know whether an UV filter is actually working properly, as the lamp will keep shining visible light long after it has ceased being efficient with regards to DNA destruction.

Are you sure the premature aging and/or low-efficiency during warm-up isn't a problem with your setup ?
I'm no expert, but my initial feeling is that you might be less protected than you think

Brann

[Brann-]

Originally Posted by thinwater

...Which is why most people ditch UV and go with either an NSF 53 rated carbon block filter (0.5 micron) or something like a Pentek Microguard (0.05 micron).

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.

[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.

[JstaRebel]

I don't imagine this post to be popular with UV users, but it is accurate. I highly suggest that anyone looking at a UV system do significant research on it before deciding if it is the right choice because more times than not, it isn't. Note the last sentence below. Turning on and off a UV lamp shortens it's lifespan. Also, using a lamp changes the dynamics of how bacteria act in your system, and turning off the lamp allows bacteria to re-grow and migrate outside of the reaction chamber. A little bleach in your tanks and a post carbon block filter is a much more effective means of insuring quality drinking water aboard and much cheaper.

ESPWaterProducts.com
HomeLearn UVUV Technical Help
uv-technical-help-title.png
How Do I Maintain My UV Water Treatment System?
How To Replace A UV Lamp
How To Clean A UV Sleeve
Harness the power of light with ultraviolet technology. In this section, access guides and manuals to answer the technical questions you may have about ultraviolet water purification systems, as well as maintenance and installation instructions.



How Do I Maintain My UV Water Treatment System?

Ultraviolet water purification is an excellent method for ensure your water is safe and drinkable. Like all water treatment systems, a UV system needs routine maintenance. The good news is, UV system maintenance is relatively simple and trouble free. Below are some areas that need periodic attention to ensure optimal performance.

Manufacturer’s Instructions and Information – Keep and Reference It!

Smiling Woman drinking water from glass
While most UV systems share many similarities, there are often some differences in maintaining a particular system. Specific information from a system’s manufacturer will be critical to maintain your system from year to year. Always closely follow the manufacturer’s maintenance schedule and instructions to avoid compromising the system. Proper maintenance will ensure your system’s effectiveness for years to come.

UV Lamp (or Bulb) Replacement – Change Every Year!

Image of a UV Lamp
A UV Lamp is the heart of the UV treatment system. The lamp needs to operate well to ensure water is safe. Unlike regular light bulbs, UV Lamps do not burn out – they solarize. This means that over time they reduce in their light wave intensity to about 60% of what a new UV lamp provides. This point is reached usually after one year, or 9000 hours, of continuous use. It is EXTREMELY IMPORTANT to replace the lamp every year on schedule. New lamps will generate a UV light dosage of near 60 mJ/cm2. Over a year’s period the UV light dosage will drop to about 30 mJ/cm2. This is the minimum dosage needed to effectively kill bacteria. At this point, lamps should be replaced. Almost all UV systems are meant to operate continuously, you can actually significantly shorten the life of the bulb by turning it on and off.

[bcboomer]

At the Vancouver boat show there was an LED UV water sterilizer that should solve the warm up issue. Very low power consumption (12 volt) and I don't think they need a warm up.

[Brann-]

Originally Posted by bcboomer

Very low power consumption (12 volt) .

Did you mean 12 Watts ? Volts is not a unit of power consumption (neither is W by the way, but Wh is !)

[Brann-]

Originally Posted by JstaRebel

Turning on and off a UV lamp shortens it's lifespan. [...]A little bleach in your tanks and a post carbon block filter is a much more effective means of insuring quality drinking water aboard and much cheaper.

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.

[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.

[Brann-]

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.

The fact that the lamp is 12v has little do to with its consumption. Voltage is not a unit that measures this. For example, a 12v hallogen light consumes ten times more current than a 12v LED light.

with regards to viruses and bacteria, there is no such thing as a sterile environment. Virus and bacteria WILL make it to your water tank. And once they are there, if left to their own devices they will proliferate. That's why it's important to clean your tank mechanically on a regular basis, and either to nuke everything with bleach on a regular basis, or to make sure the lifeforms that strive in your tanks between two cleaning sessions don't make it to your faucet (filters or UV lamp)

[senormechanico]

When cruising, we just use our Spectra and our immune systems.
It worked in Mexico for us for several years and works wherever we cruise now as well.

[bcboomer]

I think, since it is LED based, that it probably doesn't use more than 10 watts, likely less.
Such a complex system seems like overkill, unless one has a severely compromised immune system.
I expect 99% of those with a watermaker don't bother doing any filtering. We just use marina supplied water, straight up, with a small taste/odour filter. Adding a few drops of chlorine bleach to RO water would make it cleaner than most city water.

[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. I does not cycle with water flow, so the light is continuously operating. This is not a system I cobbled together, it is manufactured for this purpose. It costs $225, which is very reasonable, and includes the first year's filters and light. They recommend annual replacement of all filters and the UV light and it costs $53 for the kit and we replace them each spring after using Peggy Halls recommissioning system.

My system is just past the water tank, so after it goes through the two filters and the UV it is distributed through my manifold to all the fixtures in my system. We have great water and no problems. This is essentially what a water maker does without the UV as the water maker product water is put in a tank,and then distributed.

We have used this system for over 5 years including a 6 month trip to Florida with various water sources with no problems whatsoever. I don't care about the power draw because when I leave the dock I turn on the generator and use it until we dock and plug back in. When we are at our home marina, we use the boat about 75 days a year. I suppose you could worry about the water after the unit because the chlorine is filtered out and it stands in the hot water tank and lines to all the outlets. So far that has not been a problem as we turn over our water pretty fast.