The Caleffi SEP4™ 4-in-1 combination separator incorporates four important functions for hydronic systems: hydraulic separation, air separation, dirt separation and ferrous impurity separation. The unique geometry and design of the separator causes the connected primary and secondary circuits to be hydraulically de-coupled to prevent pump conflict from occurring. An internal screen element facilitates the coalescing and capture of micro-bubbles to facilitate high performance automatic removal, while concurrently causing the capture of non-ferrous debris particles down to 5 micron size. A powerful magnetic field induced by rare-earth neodymium magnets facilitates the capture of ferrous impurities such as iron oxide down to microscopic size thus delivering 2-1/2 times the ferrous impurity removal performance of standard air and dirt separators. The SEP4™ saves on system installation and maintenance costs as four devices are combined into one. Additionally, all captured debris is blown down through the purge valve without requiring to take the system offline.