The pressure tanks are WellMate 450.
Should the bladder in these tanks fail, it can be replaced. The tank must be drained, disconnected and taken outside for this operation.
This procedure has been done twice (to the south tank). The job took three volunteers about 2 hours to complete and could be compared to wrestling a greased pig. The bladder cost slightly over $500 (in 2009) and took almost 3 months to arrive.
Instructions for replacing the bladder can be read here.