Since there are different types of wastewater, material choice for specific sewage applications is critical for ensuring long pump life.
Occasionally – although this is rare in municipal wastewater applications – a low pH level causes corrosion and justifies the extra cost of stainless steel, which is why we have now added duplex stainless steel impellers to our range. However, wastewater is by definition anaerobic: containing very little oxygen, therefore corrosion is seldom a problem.
More often than not, the problem is not corrosion but erosion. If the wastewater you pump contains high concentrations of abrasive particles, hard iron is a better choice in the long run over cast iron or duplex stainless steel.