The Big Berkey with all 2 filters installed will PURIFY not filter, PURIFY nearly 4 gallons per hour install two more filters and it jumps to 7 gph. It comes with 2 filters for about $280 Thats good for 6000 gallons of purified water, by purify, I mean it takes out bacteria and viruses. I have two Big Berkeys one for home us and one for camp use but they are both for preps, and I keep a spare set of blacks for each.(that’s the pricey part @ $120 a pair). We use it everyday for coffee, cooking, drinking.
We're on a well; lots of iron and sulfur. We love our Big Berkey.
Agreed the filters are pricey (just got another pair in today), but clean water is priceless.
Now I need to make a system to pre-filter in case I ever need to make use of the lake behind the house.
EDIT: For the curious, Berkey test results page: Black Berkey® Purification Elements Test Results ? Berkey Knowledge Base