Chances are that the hard water leaves calcium scale on surfaces. Water pumps generally have small tolerances around impellers (the spinny bit), which would stop them turning. When electric motors are blocked from turning and constantly trying to start, they burn out and are broken.
This would happen regardless of the material.
If you cleaned off the calcium regularly, the pumps wouldn't seize and the motor wouldn't burn out. I'd suggest maybe one a month filling the bowl with a mild acid such as vinegar or cola,and most importantly, running it through the pump to dissolve calcium in and around the impeller. Leave it soak overnight.
You could also try this on your existing water foundation, but as mentioned above, the motor may have already burnt out, and in that case will need to be replaced.