passes through a .5 and a then a .05 filter then a UV light. Any dockside water gets treated with it. I first saw it used by Marc and Lynn but then saw it being used to treat all the water used at the Assua Tequila factory outside of Mazatlan. I bought mine at Downwind Marine in San Diego in '07. Marc had a nice SS stand that went with his but I just hang mine on the lifelines when in use and plug it in with the cord run through the porthole into the head. I store it in a canvas bag I made when not in use and all is good and I never worry about water. Unless, of course, you count the time the cute little girl dock attendant in La Cruz tried to help me by putting the diesel nozzle into the water tank. That was a bad couple of days!