Best impeller material: neoprene? nitrile?

[alanwilson]

I need to top up my stock of water pump impellers: the current one is 3 years old and still fine, but possibly needs to be replaced. I did try Globe (advertised as allowing dry running) but they didn't last long at all. What do people recommend: neoprene & nitrile seem to be the common materials?

 

[vyv_cox]

I don't think they tell us the composition, unless it can be found on websites somewhere. There is not a huge difference between the two. Nitrile has better oil resistance but is good enough in water. Neoprene has good water resistance but is good enough in oil. The amount of oil passing through most water pumps is pretty negligible, so no great difference on the chemical resistance side. I suspect that the wear resistance of nitrile might be a little better, but don't know for sure.

The problem with dry running is partly the lubrication but mostly the heating. No rubber will last long rubbing hard on brass, it will burn in minutes.