Submersible Grundfos SL sewage pumps (1.1-11 kW) are fitted with an S-tubeÃ‚Â® impeller. The free passage through the pump varies from 50-100 mm depending on size. The SL1 1.1-11 kW is a submersible wastewater pump with a Grundfos S-tube® impeller, offering the best solution for large flows of raw sewage, with free passage of solids up to 5”/125 mm. The SL1 from Grundfos is a tried and tested performer in the industry, designed to optimise your system with minimum servicing required. Built for durabity, easy installation and hassle-free operation, the SL1 comes packed with innovative Grundfos features that protect the pump and ensure optimal system performance for industrial and municipal wastewater applications.