Maintenance of a DWS-7 UV disinfection unit

The other day I was driving to work and thinking to my self; you know, I just don’t have enough problems, I wish somebody would give me some more problems. Well, apparently “somebody” was listening. Cut to last Sunday. We have an Ultra Violet light water disinfection unit installed on our old well because basically we are using water that is slightly above that of stagnant pond water (I hope beyond all things, I can get the new well installed this year). One of the things that is required when you use a UV disinfection unit is yearly maintenance. The bulb needs to be replaced once a year and quartz tube needs to be cleaned.

File under the category “haste makes waste” as I removed the UV bulb from the quartz tube, I pulled it slightly sideways and cracked the bottom of the quartz tube. I was immediately greeted by a steady stream of water from the bottom of the UV unit. Damn, just damn.

In the exploded view, the tube is number 16, while the bulb is number 17.
Now, secure all the valves and drain the water out, remove the brass tube retaining fittings, and this is what I found:

The quartz tube cracked to a point just above the “O” ring. The tube would need to be replaced. This is not just any glass tube, you see, it is made of quartz and is purified so that none of the UV light gets reflected back to the bulb, but passes through and into the water, where it’s germ kill qualities are needed the most. Cost to replace: $50.00. Cost for a new bulb: $73.00.

You can see the ends of the old bulb are starting to turn black, just like a florescent light bulb that is slowly burning out.

Replacement was in the reverse order, first I used a little petroleum jelly to lubricate the “O” rings. I put one “O” ring on and carefully slid the tube back into the unit. I put the other “O” ring on and centered the tube in the unit and then carefully replaced the brass retaining nuts. Turned the water back on and checked for leaks, all good.

After all that, I carefully replaced the UV bulb.

The light has and electronic ballast, much the same as any ordinary florescent light fixture. The ballast should run a little hot to the touch, but not too much. A ballast that is too hot means the bulb is getting weak and needs to be replaced.