About UV water filter/ sterilizers

anjuna mark

This is in response to a thread by Priya; however, I’m afraid that her problem is much worse than these units are made to handle. Priya, you will have to find some filter elements from plumbing supply shops locally. A UV unit will make a small quantity safe to drink though. Probably you would be better off paying someone to bring you better water; I’m sorry I have no real and practical advice for your problem.
Anyway, here’s what I learned of the UV drinking water filter units available in India;


Water filters + sterilizers of India; by Mark Holden, 2008
I did some research on these some years ago. I believe what I learned then will still be current.
Pure filtering by a good filter element will remove most or all bacteria, but not viral particles. Standard practice of filtering + boiling is very effective, but time and fuel consuming. Also, the water is prone to re-infection as it cools.
I bought a UV sterilizer soon after they came onto the market in India. I made a lot of trouble for the salespeople first, making them open up the units and show me how they work. I’ve been using two units [one at home and one in my camper] for about 10 years now, whenever I’ve been in India.
First, how it works; all the units of this type work exactly the same way, and are equally effective when working properly. Water under pressure [very little is needed, a 1 meter tank height will do] is forced through a fine fabric sock, and then a ceramic element to remove particles and dirt. In a cavity in the center of the filter element, activated charcoal is usually [not always] packed in. Activated charcoal absorbs oily chemicals, and will improve the taste of some water a lot. Other water doesn’t need it, and some contaminants pass right through. Salt and dissolved minerals are not absorbed, so brackish water will still taste terrible, although it will be safe to drink.
After the filtering, the water is passed through the important part; the UV chamber. The UV chamber is a stainless steel tube about 5 cm in diameter and 18 long [I’m working from memory here, so these numbers are dodgey]. Inside the metal tube is a quartz tube [the most expensive part]. The water flows between the quartz and stainless steel. In the middle, protected from the water by the transparent quartz tube, is a florescent type* 8 watt ultra violet tube lamp.
The UV doesn’t actually kill the bacteria or viruses, but it completely inactivates them, rendering them unable to reproduce and therefore harmless.
There is no loss of water, and power usage is very slight. I run my mobile one from the truck battery.
Disadvantages; they do need maintenance.
I had mine maintained by a guy who came to the house every few months when I wasn’t there to do it myself. He disconnected all the safety warning circuits instead of repairing them, so when the UV tube failed, no one noticed until I took it apart myself for cleaning.
Dirt can coat the inside of the quartz tube and block the UV from getting through, and fluid flow has to be kept just right, at 2 liters per minute, to be sure that the water has had ample exposure time. If you use charcoal [I do], it has to be replaced from time to time [very much depends on how much water you’re filtering as well as the nature of the water]. The ceramic filter section also has to be dismantled and cleaned regularly. It gets blocked by the dirt it’s keeping out of your water.
The more expensive units have a solenoid valve that only switches the water flow on a minute after the UV tube is lit, and will not switch on if there’s dirt on the tube, if the line voltage is too low, or if it doesn’t light at all. The solenoids are expensive to replace when they fail, which they sometimes do. Simple cheap ones need to be checked manually, and you have to wait after switch on for a minute before you use the water.
As the electronics as well as the maintenance people tend to be unreliable, I prefer the cheap unit, and I drill a small hole in the end of the outer casing so I can see the UV shining through so I know it’s working. I connect it to the voltage stabilizer of my fridge to be sure it gets ample voltage.
But the ‘Aquagaurd’ UV filter / sterilizer is the best for most people in my opinion, although it has some drawbacks as well.
It’s considerably more expensive, and it has a big gaudy outer casing. But it has superior electronics; it has its own voltage correction circuits that handle big fluctuations and low voltage, and good solid safety circuitry. All this is only as good as the maintenance person who looks after it. The company [at least in Goa when I grilled them 10 years ago] trains its staff well.
So; if you do these kinds of things yourself, and/or live in an area where company trained maintenance people won’t come to clean and check your unit for you, I’d go for a cheapo [mine was US$50. At the time]. If you can afford it, and live where service is available, go for the Aquagaurd [someone please post current price list!!].
Other filters;
Drip type filters are better than nothing, and we all used them in the old days.
Filters that add chemicals are not filters, but treatment systems. If you like to consume chemicals, I suppose they’re fine.
Reverse osmosis filters; if anyone tries to sell you one of these, I don’t believe them.
A reverse osmosis filter is so fine, it will remove salt molecules from water. They are high maintenance, and require special very high pressure pumps. They are VERY expensive. Most so called reverse osmosis filters sold for the home are nothing of the kind, but a marketing scam.
Clean drinking water is extremely important for everyone living in countries like India. Bottled water is simply tap or well water that’s sterilized at a factory. It’s expensive, inefficient, and unenvironmental; but depending on your personality and circumstance, may work better for you. Please just recycle the bottles. That shouldn’t be too hard, should it? The hills and beaches of Goa are littered with countless thousands of discarded water bottles.

*Strictly speaking, it is not a florescent lamp; but since it looks like one, and uses the same fittings and electrical circuit, the term works best to describe the UV tube. It is not the same as a “black light”, only because it uses quartz instead of glass for the tube. Glass absorbs UV light, quartz doesn’t.

Nick-H

My reverse osmosis unit was very expensive .

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Just one member of the IndiaMike Mod Team