Bentonite pellets are used for the sealing of water, monitoring and piezometer wells. 

Bentonite pellets when properly located provide an impermeable flexible barrier between aquifers; they are also used to prevent contamination from surface water into the well. Bentonite pellets can also be used to backfill or abandon all types of bore holes or seal in surface casing.When exposed to fresh water Bentonite pellets will swell and expand to fill voids exerting pressure against all surfaces to create a flexible low permeability seal. Bentonite pellets does require any mix equipment and can simple be poured directly into place even through standing water without sticking together.