Key Information - Universal head negative positive - Heavy duty brass pump - Twin and single impeller - Regenerative range - Continuously rated - Anti-vibration feet - Supplied with stainless steel braided hoses The Grundfos Amazon Universal Positive and Negative shower pump is perfect for boosting water pressure in domestic or light commercial hot and cold water systems up to 4 bar. These pumps are ideal for properties with up to 4 bathrooms wanting to boost multiple shower heads. Universal pump for use in both positive and negative head installations. Deciding on the most suitable kind of pump is a major decision, but once you decide that shower pumps are going to provide the best solution then the Grundfos Amazon Universal Head Twin Impeller 3.0 Bar Shower Pump STN-3.0 B -.