We have had two pumps through our shop, in 2011, that the pump housings were totally eaten away causing a failure of the pump. It first appeared to be bad water systems or operator error, however when the second showed up, we begin noticing the the intake strainers were being replaced more often that usual. Both apparatus have polytanks.
A third apparatus from 2010 that had a pump failure, had the same damage as the two new pumps. The 2010 repair, originally had a steel tank, but it was replaced with a poly tank in 2001.
The steel tanks had anodes placed in each baffled compartment to disapate the the electrical current produced by the water moving in the tank. Looking at all 3 volutes, they show the same deteriation which allowed the grooves that hold wear rings in place to fail.
We believe, after talking with other pump repair facilities and pump company service managers, that the electrolysis is being passed to the pump volutes during pumping operations as the polytank has no anodes to disipate the electrolysis within the tank.
Departments may want to look at adding anodes to their pump housings to prevent a pump failure. The cost for the repairs is running between $20,000.00 and $26,000.00 depnding on damage. It appears to be happening to apparatus 16 to 20 years into their service and an active engine company. All three departments had excellant water systems and used hydrants for water supply.