The present invention relates to a liquid metering device (1) for metering pumps which is formed by a main longitudinal conduit (2) with a first and second opposite ends (2.1, 2.2) comprising a fluid inlet (3) at the first end (2.1) located perpendicular thereto, a first outlet (4) at the second end (2.2), and a first connection (5) to backpressure control means (6), a second connection (7) to safety means (8), acting in parallel and in an independent manner, and a second overpressure outlet (9), arranged in one and the same connecting section (10), and where said connecting section (10) has an inclined wall (11) allowing the fluid to exit through the first outlet (4) for a fluid pressure equal to or greater than a fixed backpressure value and the fluid to exit through the second outlet (9) for a pressure greater than a fixed value.