Categorized | Reverse Osmosis

Warning: Don’t ever put a UV light on an undersink reverse osmosis system!

I have to admit that we used to sell an under-sink reverse osmosis system that included an ultraviolet or UV light, but if you look on our site now, you will not find anything of that type.  Many of our competitors do have such systems, however.  We have decided that we will no longer sell an undersink UV for a reverse osmosis system.  Are we missing the boat?  Well, I am going to present you with the facts and you decide.

First of all, why do you want an ultraviolet light on your reverse osmosis system?  Likely you will say that you want UV so that you can make sure your water is pure and free of bacteria.  A reverse osmosis system filters down to below .001 microns, but the smallest bacteria is larger than .01 microns, so theoretically, a RO system should not allow any bacteria to pass through.  However, if you look at almost any reverse osmosis system manufactured by any credible manufacturer, you will find that it says “Not for use on water that is not microbiologically pure.”  This is because a RO system has mechanical seals and o-rings that could become compromised or fail, so you should not rely on reverse osmosis for bacterial purification.

Here’s one problem:  Even if your water is contaminated with bacteria, you still bathe, shower and brush your teeth in it.  A couple of years ago, I showered in contaminated water in Haiti and got infections in both eyes.  It wasn’t fun, I can tell you for a fact.  If you have children or grandchildren, you know that they drink from anywhere, even the bathtub.  An ultraviolet light on the RO system does nothing for the rest of the water in the home.  You would be better served with putting an ultraviolet light on the incoming water supply to treat the water before the reverse osmosis system, so that you are not installing the RO system on water that is microbiologically contaminated.

Here’s a second problem:  An ultraviolet light on a reverse osmosis system under your kitchen sink heats the water as it sits during the day or night.  It’s almost hot enough to make your coffee in the morning!  You could turn the UV light off, but then you could not be sure if your water was pure and turning the bulb on and off would shorten bulb by by up to 300% – not a good idea.

The third problem:  The heat generated by the UV light bulb can weaken fitting, embrittle plastic tubing and create a leak in certain circumstances.  That’s really pretty undesirable in most modern kitchens.

The forth problem:  To put a UV under your sink, you need electricity.  I have heard people say “I have electricity to my garbage disposal” and they do, but your UV system will only work when you turn your garbage disposal on (not a good idea).  You need to run an additional electric line to the ultraviolet system and that can often be a problem.

The final (fifth) problem:  Most undersink ultraviolet systems are cheap plastic Asian Import models or cheap, poorly designed stainless steel Asian Import models.  I’ll be kind and just say that they inherently have a lot of problems, not the least of which are leaks.

So, if you want a UV for use after your reverse osmosis system, the odds are, once you weigh the pros and cons, you will decide against it.  The best solution is to install a ultraviolet system on the point-of-entry (POE) into your home so that all of the water in your home is bacterially pure.

3 Responses to “Warning: Don’t ever put a UV light on an undersink reverse osmosis system!”

  1. Andy Meyer says:

    Thank you for the info on U. V systems location. I use Severn River (Ontario Canada)water thru a UV and am installing a R.O. system and was about to mount the R.O. ahead of the U.V. as shown on most Water Purification Companies web sites. Thinking about it over night I said to my self, currently I’m killing the bacteria on all my incoming water, now if I change I’m only treating the drinking water not the rest. Your site has just verified what I was thinking and given me confidence to go ahead. I will have it tested of coarse. The UV heat issue is also very real and very interesting. My unit is in the basement, 20′ away. Andy

  2. Bill Chianti says:

    Is bacteria a problem in the storage tank of an under-sink reverse osmosis system?

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