A process transmitter for measuring a process variable of a process fluid, the process transmitter comprising: a pressure sensor for measuring a pressure of the process fluid; a sensor housing having a hydraulic passageway; a hydraulic system for providing a communication channel in the form of a hydraulic connection between the process fluid and the pressure sensor, the hydraulic system including the hydraulic passageway that is coupled with pressure from the process fluid at a first end and the pressure sensor at a second end; and a first fill fluid (36; 46) in the hydraulic system, the first fill fluid comprising: a first hydraulic fluid for transmitting the pressure of the process fluid to the pressure sensor; characterised in that: the first fill fluid further comprises a non-metallic-based stop-leak composition for sealing leaks that develop in the hydraulic passageway of the hydraulic system; and the hydraulic system includes a remote seal that allows the hydraulic passageway of the hydraulic system to be extended beyond the confines of the sensor housing of the process transmitter, wherein the remote seal includes a capillary tube charged with a second fill fluid, comprised of a second hydraulic fluid and a metallic-based stop-leak composition, that is isolated from the first fill fluid of the hydraulic passageway by an isolation diaphragm which separates the first hydraulic fluid in the hydraulic passageway from the second hydraulic fluid in the capillary tube, the metallic-based stop-leak composition being for sealing leaks in the remote seal of the hydraulic system. a pressure sensor for measuring a pressure of the process fluid; a sensor housing having a hydraulic passageway; a hydraulic system for providing a communication channel in the form of a hydraulic connection between the process fluid and the pressure sensor, the hydraulic system including the hydraulic passageway that is coupled with pressure from the process fluid at a first end and the pressure sensor at a second end; and a first fill fluid (36; 46) in the hydraulic system, the first fill fluid comprising: a first hydraulic fluid for transmitting the pressure of the process fluid to the pressure sensor; characterised in that: the first fill fluid further comprises a non-metallic-based stop-leak composition for sealing leaks that develop in the hydraulic passageway of the hydraulic system; and the hydraulic system includes a remote seal that allows the hydraulic passageway of the hydraulic system to be extended beyond the confines of the sensor housing of the process transmitter, wherein the remote seal includes a capillary tube charged with a second fill fluid, comprised of a second hydraulic fluid and a metallic-based stop-leak composition, that is isolated from the first fill fluid of the hydraulic passageway by an isolation diaphragm which separates the first hydraulic fluid in the hydraulic passageway from the second hydraulic fluid in the capillary tube, the metallic-based stop-leak composition being for sealing leaks in the remote seal of the hydraulic system. the first fill fluid further comprises a non-metallic-based stop-leak composition for sealing leaks that develop in the hydraulic passageway of the hydraulic system; and the hydraulic system includes a remote seal that allows the hydraulic passageway of the hydraulic system to be extended beyond the confines of the sensor housing of the process transmitter, wherein the remote seal includes a capillary tube charged with a second fill fluid, comprised of a second hydraulic fluid and a metallic-based stop-leak composition, that is isolated from the first fill fluid of the hydraulic passageway by an isolation diaphragm which separates the first hydraulic fluid in the hydraulic passageway from the second hydraulic fluid in the capillary tube, the metallic-based stop-leak composition being for sealing leaks in the remote seal of the hydraulic system.