Traditionally, wastewater pump owners have faced a trade-off between larger free passage and high hydraulic efficiency. Several attempts have been made to increase the reliability level of wastewater pumps. Various kinds of impellers have been developed over the years, such as vortex, semi-open to single- and multi-channel impellers, and other more sophisticated creations. In addition to this, the very nature of wastewater is challenging, with dry solids content varying over time. Water use has not remained static either.Grundfos offers a solution to all these issues in the form of the S-tube impeller. The S-tube impeller is a tube-shaped impeller placed in a pump housing that matches the smooth tube shape through the entire pump with no obstructions or dead zones through the hydraulic. The simplicity of the S-tube impeller eliminates the need for advanced and costly add-on assemblies, which are designed to cut, shred or treat the wastewater as it flows through the pump.With the S-tube impeller, the efficiency is higher compared to other wastewater impellers as there are no edges, dead zones or cutting functions that get worn over time. Besides, the S-tube impeller features an innovative and patented labyrinth and sealing system for years of trouble-free operation.The S-tube impeller offers the highest hydraulic efficiency and best-in-class non-clogging capabilities for optimum reliability and lowest life cycle costs. The S-tube impeller and the new tube design through the pump provide many solutions. They are:• Efficiency: World-class hydraulic efficiency up to 84 per cent without compromising free passage.• Free passage: Spherical free passage up to 160 mm, meaning better solids handling and greater non-clogging capabilities.• Simplicity: A design as simple and robust as a tube results in longer lifetime and lower maintenance costsThe difficulties in designing high-efficiency impellers have traditionally been challenges with sealing against backflow, vibrations, abrasive wear and clogging. Interestingly, when Grundfos tested the S-tube in many wastewater installations across the world prior to its release, the company observed that, customers experienced substantially lower noise and vibration levels, reduced maintenance, and far better non-clogging capabilities than ever experienced previously.The S-Tube impeller is compatible with SE and SL ranges of pumps by Grundfos. The SL pump is designed for the transfer of drainage and surface water, domestic, municipal and industrial wastewater, and process water.