Impellers are always replaced, rather than repaired. The only exception to this is
when impeller vanes are being "shaved" to reduce pump performance. After
shaving, the impeller must be rebalanced, to avoid pump damage.
Volutes (Pump Bodies)
Cracks in the volute normally result in replacement. It may be possible to braze or
weld these, but it is rarely worth the effort.
Whenever the volute is pulled apart for any pump repair, the gasket between the
volute halves, or the volute and the bearing assembly, should be replaced. If old
components are simply being reassembled, the old gasket can be used. However,
it is better to scrape out all the old material, and use a new gasket.
5.2 REPAIR PROCEDURES