Alternative Technology Assn Forums

1. 

   wlb
   Member

   We sometimes get a slimy residue around parts of the inside of the drinking water filter housing from the rainwater tank, on the upstream side of the filter. It takes months to accumulate to a point where you can find it.

   It just occurred to me that there are probably UV LEDs available now for water sterilization, so I went Googling. I only found two.
   One expensive American device specifically for this purpose, and a very cheap Polish unit intended for aquariums.

   http://tinyurl.com/lf3cmfk

   http://tinyurl.com/lep949q

   I'm considering the American unit because it's designed specifically for drinking water. The Polish aquarium unit may not be made of food-grade plastics etc., but tropical fish can be fairly sensitive things, and the water is recirculated, so you would expect the materials of construction to be suitable for contact with potable water. The other possible disadvantage of the aquarium device is that the water is recirculated, so it may take many passes to fully sterilize, whereas the US device is designed for a single pass.

   I'm just curious to know if anyone else has considered something like this or seen something similar.

   Posted Wednesday 26 Feb 2014 @ 3:45:42 am from IP #
2. 

   Lance
   Key Master

   There's one area where LEDs are not as good as fluoros and that is producing shortwave UV light. Typically, 20mA shortwave UV LEDs produce less than a milliwatt of output for 80mW or so of input, fluoro UV tubes do better, especially on a cost per output watt basis.

   I get asked to price these things regularly and good quality shortwave UV LEDs are damned expensive, there are some cheaper chinese versions but even they are expensive.

   Of course, these units might be using longer wavelength UV-A (390nm or so) UV LEDs, they are much cheaper for high output, but you need more output to be effective. Normally water sterilisation is done at UV-C frequencies as it is considered ionising radiation and kills bacteria etc much faster.

   Posted Wednesday 26 Feb 2014 @ 7:10:07 am from IP #
3. 

   wlb
   Member

   Thanks Lance.

   I was originally just going to email you and ask if you knew of anything. Then I thought that it was just being lazy and you'd probably have to do a search yourself. So I did it instead. The odd thing is that the $300 US unit doesn't mention which part of the UV spectrum it uses, but the $25 Polish unit says it employs UV-C.

   Posted Wednesday 26 Feb 2014 @ 11:08:14 pm from IP #
4. 

   Greg
   Member

   Have one of these ( http://www.psifilters.com.au/tank-water-filters )- no issues since purchase 14 months ago. Good info on the website as well.

   Posted Wednesday 26 Feb 2014 @ 11:16:41 pm from IP #
5. 

   wlb
   Member

   Thanks Greg.

   It looks similar to the Cuno system (minus UV lamp) that we had on our previous house in the suburbs. I was planning to use another Cuno (or similar) and add the UV, and it seemed logical to look into LED developments in that area. I like the idea of LEDs instead of a tube, and I'm sure that the PureUV unit is high quality and works. Yacht owners tend to be fussy. I'm also sure that I could successfully couple that LED unit with my Cuno filter system.

   But, based on Lance's info, it looks like LEDs in this application is still in its infancy. It's also hard to go past an endorsement for a local supplier from someone who uses the equipment. By the time I get one of the PureUV units landed here it will cost as much as the complete PSI unit.

   Does the UV lamp run the whole time?
   Are you running a pressure pump? (We're just gravity feed from a header tank)

   Posted Thursday 27 Feb 2014 @ 12:08:54 am from IP #
6. 

   Greg
   Member

   Yes the lamp runs continuously but since the power point is adjacent its normally turned off.
   Yes we run a pump and an accumulator (pressure tank). Incidentally I did notice that you can purchase a booster pump (think that is what its called)that runs on the outlet of your header tank to give better pressure.

   Posted Thursday 27 Feb 2014 @ 6:53:40 am from IP #
7. 

   wlb
   Member

   Thanks again for the link Greg.

   I asked a few technical questions yesterday via their website's email page, hoping to get some answers in a day or two. Instead, I got a phone call shortly afterwards as they felt it was easier to answer my questions that way. I had a long and helpful chat, and got answers to questions I hadn't yet thought to ask. Very impressed. Lots of helpful suggestions about how I could achieve my particular needs.

   Posted Thursday 27 Feb 2014 @ 11:20:16 pm from IP #

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