I've used the Aqua Rain ceramic filters for years with no problems. I'd periodically scour the outsides of the elements when the flow slowed down. At some point in the past 2 years, I read up on the Black Berkey elements and while I don't have the fact sheets for comparison in front of me, felt that the Black Berkey's were superior in what they removed. They are not ceramic and I really don't know what they are made of but they are cleaned the same way: Stiff brush or Scotchbrite pad. Now to my problem and why I see them as not viable for a longterm survival situation: When you first unwrap them for use, you need to 'purge' them with pressure from your faucet. They come with a 3/8" rubber washer that you stick on the threaded end and hold up to a faucet for 30 - 60 seconds. All fine and the water tasted great and felt 'wetter' when drinking it. Every 3 months, my flow all but stops at some point in the upper tank. This could be at 1/4 to 1/2 of the upper chamber capacity. At first I would take them out and scrub the outsides and put them back in and while this would give me 2 to 3 fillings, they would stop again. Some Googling led me to attempt another purge under the pressure form the faucet along with a cleaning and this seemed to do the trick for another 3 months. We are running 2 filters in a 2 Gallon system and we drink enough water for me to refill it completely every night. Still not enough to clog the filters in my opinion. I also run the Fluoride removal post-filters but that would have no effect on the main filters. My city water supply comes from a reservoir about 2.5 miles away and that reservoir is filled from Mt Hood runoff. It is quite heavily chlorinated and while the filters remove 100% of the Chlorine smell and taste, I do not know if this is what's affecting them. What bothers me a little about the Large Berkey system, the Travel Berkey system and the 16 spare Black filter elements I have is that while I have water pressure, I can continue to purge them quarterly. If I lose this pressure and my filters stop up in the manner they are now, I'll have to toss them for lack of a way to purge them. Am I somehow building an airlock in them? Is the chlorine or whatever else is in my water adversely affecting them? Does anyone know what they are made of? Maybe I should cut one open next time I change them out to see whats happening on the inside. I really want to use them but am afraid that in a SHTF situation, I'll not be able to keep them running.