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How does a Lavac work?
Simplicity itself. After use, close the lid. Pump the handle of the Henderson Mk V pump a few strokes and you are done. No levers to position, no bypass valves to set, no tiny little piston pumps. When you pump the handle, the closed lid seals the system. Suction is formed which empties the bowl and, at the same time, draws in more rinsing water.