Devices for cleaning vessels, especially swimming pools, are discussed. The devices may include a non-linear flow path in a gap surrounding an in-line valve. This non-linearity permits lengths of concentric pipes forming the gap to be decreased without sacrificing operational performance of the devices. Valves forming parts of the cleaning devices may be diaphragms but shaped, sized, reinforced, or configured differently than existing valves and may have collapsible segments whose interior shape resembles an ellipse in transverse cross-section. Co-molding of diaphragms and pipes may occur, and inner and outer cups may be used to fix relative positions of various components of the devices.