A liquid supply/drain conduit system that is equipped with an inner leakage detector and a liquid process tank that is equipped with such liquid supply/drain conduit system are disclosed. The liquid supply/drain conduit system includes a first conduit for feeding a liquid into an inlet of a first valve of the normal-closed type, a second conduit of T-shape that has a horizontal portion and a vertical portion, the horizontal portion of the second conduit flows a liquid from an outlet of the first valve into a reservoir tank. The second valve of the normal-open type has an inlet and an outlet, the inlet is situated in relation to the first valve in such a way that it receives through a vertical portion of the second conduit a leaked flow of liquid by gravity when the normal-closed first valve failed to close. A liquid detector is further provided for detecting a leaked flow of liquid through the second valve. The leakage detector may optionally include an alarm system to be activated when a leakage flow is detected. The leakage detector may further send a signal to a process controller for alerting a machine operator of the leakage status of the liquid supply/drain conduit system.