Penstock in compact design in self-supporting stainless steel frame for round openings. Can be installed with chemical anchors directly upon delivery. Ready for operation immediately after installation. Pre-installed seal of wastewater-resistant EPDM in a flexible holder between sliding plate and frame that can easily be replaced without disassembly of penstock. Due to this separation the penstock perfectly seals to the mounted wall and sliding plate and is even able to level structural variations. This patented seal is not affected by insufficient frame stability and frame distortion which are otherwise common causes of leakage on penstocks. The stainless steel construction provides maximum corrosion protection and all acid is cleaned and passivated in own pickling plant. Fixed spindle with self-cleaning spindle nut. Built-in storage shelf for manual operation, can be equipped with electric or pneumatic actuator. Leak-proof in accordance with EN 12266, table A.5, class C.