Black Berkey element replacement
Black Berkey elements are rated for 3,000 gallons per element (6,000 for a pair). At 2 gallons/day household use, a pair lasts approximately 8 years -- the longest filter life in the countertop filtration category. The "trickle test" is the practical replacement indicator: if fully primed elements produce less than 1/2 inch of water in the lower chamber per hour in normal conditions, the elements are expired. Replacement elements are available at berkeyfilters.com and authorized retailers (Natural Grocers, REI, Amazon).
PF-2 fluoride add-on replacement
PF-2 fluoride filter elements rate at 1,000 gallons per element (2,000 per pair). At 2 gallons/day, replacement approximately every 2.7 years. The PF-2 elements thread onto the stem below the Black Berkey element -- they're a straightforward unscrew-and-replace service.
Spigot replacement
The stainless steel spigot on Berkey systems can develop a drip at the valve stem over time. Replacement spigots (plastic or stainless, in multiple thread sizes) are available from Berkey. The spigot threads into a standard hole in the lower chamber -- remove the old spigot, apply thread sealant (Teflon tape) to the replacement, thread in hand-tight plus a quarter turn. Do not over-tighten on stainless steel threads.