Many tanks are constructed in two pieces that are joined either before the tank is delivered or after it arrives at the site. The seam may be located near the top of the tank (top-seam) or near the midsection (midseam). Regardless of the location, the seam must be rendered watertight for proper system function.
Concrete
For concrete tanks, a butyl rubber or asphalt-based (bituminous) mastic is placed in the seam before the pieces are joined. Sealant compounds should conform to ASTM Standard C-990 and AASHTO M198-75B standards that specify relative amounts of butyl rubber and fillers used in
