Abstract: Adjustable weir apparatus (101) with a wellhead separator system (6) fed by petrochemical source (1) with oil box (24) and water box (23) along with outlets for oil (25) and water (18). An adjustment assembly (12) may pass through a stuffing box (7), into a wellhead separator system (6), by way of a linkage assembly (13) connecting the adjustment assembly (12) to the adjustable weir assembly (5). The adjustable weir assembly (FIG. 5) may include an o-ring (34), a tube pin (15), an adjustable tube (22), and a nipple adapter (35) to allow adjustment while still maintaining an environment sufficiently proof against leakage.