Abstract: A sludge clarifier vessel bottom is disclosed which, in one embodiment, includes a bottom wall of the vessel and a portion of a steel side wall of the vessel, the walls intersecting at a corner, the bottom including the walls and a primer coat thereon, an amount of putty in the corner a resin base coat on the primer coat, fiberglass cloth on the resin base coat and a top resin coat on the fiberglass cloth. In one aspect crack controlling apparatus according to this invention is disposed beneath the plastic coat and the plastic coat is, preferably, not bonded to the crack controlling apparatus. Also disclosed are clarifiers with such bottoms.