Hot or cold-water circulation pump with 0.4-2.25 HP motor, suitable for installation directly on the pipework of civil and industrial heating, air conditioning, refrigeration, and sanitary water systems. Suitable to pump clean liquids, free from solids or abrasive substances, not viscous, not aggressive, not crystallized, chemically neutral. The Pump body and motor made of cast iron sealed with carbon/ceramic mechanical seal, and has a built-in protection system to stop it when it is overloaded.