Does UV water purification work?

Can you describe the "stuff" clogging your filters? could it be a tank coatings system come undone? Or could it just be the aluminum oxididzing and giving up flakes and powders? Do you have an inspection manhole to gain access to the tank. Old boats and even young boats should have their potable water tanks "super chlorinated" to kill bacteria once every three years throughout the system from tank to taps. UV works great for bacteria and bugs but won't help you with your solids or debris suspended in your tank & clogging your filters. If you can't get to the inside of your tank through an inspection port than you'll need to agitate it's contents as much as possible and keep pumping it out. It really sounds like you need access and a tank coating applied though.

UV only kills bacteria not larger "stuff" that woudl clog filters

What do you have in the filters, algea? Only thing you can really do is remove the filter, refill th tank with fresh dock water, add a bit extra chorine and run the pump to empty the tank, repeat and then reinstall new filters

For super chlorination you'll need to know the capacity / gallon volume of your tank.
If you use household bleach you'll be adding 1.5 quarts per 100 gals. If you purchase pool chlorine or the " high test " sodium hyper chlorate " you'll be adding 4 oz per 100 gals. You need to keep it in your tank for a minimum of two hours and then fill your branch water lines or circuits to sinks and showers etc by running the showers and faucets until you smell the chlorine . Turn the taps off so the lines are full of the H 2/0 chlorine solution and let them sit for two hours. This will break all sorts of crud loose in the lines and sometimes your water will look like root beer from all the solids being broken up. Just keep filling and flushing. I have to warn you though, it will take more than a few tank fills and empties to rid the system of the taste and smell so if your wife isn't keen on brushing her teeth as it now stands, she's not going to be impressed with your attempt to keep coliform off her Oral B .

On a slightly different note: How long was it since the filters were changed? It is not unusual for a brown rust looking stuff to appear in fine filters, if left long enough it will look much worse than it is.

I use Listerine, and that works great for us, we don't drink it neither. (also good for your wifes teeth)
See:http://www.listerine.com

I knew a striker that ran a UV system, we drank the water all the time, tasted great.

When rinsing the system thru your faucets, remove the aerator (screen) before they get plugged up.

What everyone above said is true, remove water filters, do the bleach trick, make sure your watermaker freshwater rinse valve is shutoff when you do this. Put it new waterfilter elements after running several tankfulls of clean water. A couple of 1.75Liter bottles of cheap Vodka works well also, and is a good freshwater system winterizing agent in a pinch. Adding un-filtered city water and rotating it monthly will help keep this from happening. The worst thing people do is filter the water when filling the water tank and take the chlorine out of it.

Just to clarify things, Chlorine kils bacteria; UV only sterilizes the bacteria so that it can't produce colonies in your gut. Therefore, it causes you no harm. You have two options: use chlorine and drink dead bacteria, or use UV and drink the bacteria live. Much better to drink it live and the water remains clear with no sedement.

That is a unique way to look at it.

I think enough junk is in any water. Kill the critters, filter them and the dissolved/suspended solids right before the tap.
Never thought about it before, showering with dead critters should be O K.

A couple of points. If the tank isn't cleaned of suspended sediments the UV won't be able to penetrate the flow past the lamp to kill the Cryptosoridium and other bugs, clear filtered water is a requirement for UV to work properly. Size the UV system for the amount of flow. There's also a couple of bugs like Copepods that will dive for cover in the bottom sediment and live through the super chlorinization process unless the tank is either agitated and emptied or manually cleaned, empty and inspected. if you have access to the inside of the tank than a epoxy potable water tank coatings system will go a long way . Once chlorination has taken place and the tank has been flushed of the Taste and smell , you won't be drinking any bugs, dead or alive.

I'm servicing a system next week. Course, fine and UV cartridges. Made by Pura.
Should filter about anything before the light hits it.

Yes, A clean tank is the best start always.

I didn't know a combo like that existed Ralph, that's the Finest kind !! 22 watts of UV is the terminator for sure. I always had stand alone stainless casings with the UV tube.
Good to know these exist.

I did not know much about these big gizmos till today. Reviewing work orders, I had to go to the boat today and get the model number. Pura has a nice web site with lots of options. Seem somebody had some buck$ when they installed it. But, I am impressed with it and it should offer a heck of a system. 20 inch filters, 20 inch submerged lamp in the third can.

On the other hand, on our boat with stainless tanks, we have never had a problem after 11 years. It gets used.
Wife insist it gets dumped and refreshed before any deployments. We do make our own R/O water when away, it gets used up quickly and flooded with shore side (chlorine) water when we return.

I guess the best way to avoid water problems is to keep fresh chlorine water on board. Dump it and refill a few times a year if it's a dock queen.