Reluctant to scrap good working pumps, I will normally keep a few on shelf as replacements in event of call out.
Problem arises when pump that worked perfectly in April refuses to rotate in October.
My solution is a 13 mm socket on a 3/8" drive extension fixed in a drill chuck. With piece of leather between socket and impeller (tongue of old boot is ideal) a drill can be used to rotate impeller. Held with impeller down and introducing boiled water via the bleed screw hole will normally suffice to free up the movement to the point when motor can be switched on to take over. Once running on motor I continue to top up water via bleed hole until pump running silent and smooth.
If others have a way of storing pumps to minimize seizure I will be grateful to hear.