Cindy, My wife and I own a Big Berkey and love it. We've used it daily since last summer. I think it's one of the best kitchen items we've purchased. Here's were I bought it from: http://www.safe-water.com/ap/a273sw/index.html(posted 9654 days ago)
LINKThe initial cost isn't cheap, but it's a good value. The filters last a long, long time and can be cleaned by running them under running water or wiping with a cloth. You cna actually take water put of a mud puddle, filter it in a Big Berkey, and drink clear, fresh-tasting water. The filter is very efficient. As far as I know, there isn't a more efficient one on the market. I think it's better than the Culligan reverse osmosis stytem we used to own. It's much better (and less expensive to use) than Brita, which we've also used.