Grundfos STN-4. 0 B GBQP Shower pumps are used for boosting hot and cold water in showers, bathrooms or whole households. Shower pumps allow customers to boost performance and have a more powerful showering experience. The premium Amazon 4.0 bar brass positive twin impeller shower pump is a continuously rated regenerative pump suited to domestic, commercial or light industrial use – able to transform any compatible shower system into a true power shower. Heavy duty brass impellers and machined brass stampings, Long-life silicon carbide seals, Anti-vibration feet for minimal operating noise, Supplied with stainless steel flexible hoses, 2 year manufacturer’s warranty.