In general terms, the present invention relates to a safety valve or a pressure relief valve (PRV) that is developed to be used in combination boilers and similar appliances and utilized for the purpose of controlling or limiting system pressure. Relief valves are generally used as safety devices in systems where fluid pressure is important, and they reduce the system pressure either by discharging fluid from the system or simply by interrupting the fluid conveyance in case of an emergency when there is an increase in pressure. The present invention relates to a pressure relief valve, the rear cover of which is attached to the body by means of a clawed structure and manufactured from entirely recyclable thermoplastic material.