How to store the flexible rubber impellers if engine not used for long time

Proper storge of the impellers during a prolonged lay-up can help maintain the life of the impeller.
Remove the impeller from the housing and store in a cool,dark place.
Above will avoid the following:
1.Copper bonging of the impeller to the housing.
2.Ultraviolet deterioration.
3.Vanes setting into position as stored in the housing.