Orion® T16 sampling tank shall be 5 USG, 11 in Dia x 16.25 in H, cylindrical, seamless, stress and defect free, rotationally molded construction to uniform wall thickness from virgin PE resins conforming to ASTM D 1248, with single FNPT inlet and outlet as standard. All penetrations shall be heat fused to tank wall. Non-load bearing flat cover shall be bolted and gasketed to tank and shall have centrally located NeutraGuard pH probe insertion assembly.