It goes at the same rate as the Berkey since it is using the same filters. It is about two to four gallons an hour, depends on how bad the water is before you filter it. You can built it with the ceramic or there black filter, they sale them as replacement for the Berkey system. Here is a website that sells the Berkey click on the specs where they give you the rates. http://www.berkeyfilters.com/berkey-water-filters/big-berkey.html?gclid=CJ_JzpnfgcACFZTm7AodElEAvA
By building one the way I did you save a lot and you can make three for the price of one Berkey.