Enabling single-hole penetrations for piping, flanged through-the-wall pipe fittings are available in PVC, stainless steel, and Hastelloy in sizes for 2 to 12 in. piping. Wide, thick, gaskets tightly seal fittings under externally adjustable force against tank walls. Units are equally suitable for new and existing steel, and for concrete tanks with or without epoxy or glass coatings, or with membrane liners. Virtually maintenance-free, fittings are removable for repeated installation in other tanks.