4
Replace the gasket around the disk at the bottom of the pump arm shaft. Also replace the butterfly valve (often a simple leather flap) while you have the unit opened up. Remember to apply any provided lubricant to the gasket to get the longest life from the seal.

5
Reassemble the pump, remembering to put water on top of the disk (priming the pump by holding the valve closed for the first few strokes to build vacuum) as it is put in place.

6
Pump the arm, noting any roughness to the stroke or if the disk seems to bind at any point. If there is water in the well and the tube is intact, a few strokes should draw water up.

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