Abstract: Vacuum pressure applied to a hydrostatic chamber causes a rise of carrier liquid from an underlying flow stream to an equilibrium level in a hydrostatic column passage and stacking of floating liquid thereabove for separation from the carrier liquid by overflow into siphoning passages conducting the floating liquid to a recovery container vented to atmosphere. The liquid conducted through the siphoning passages seals the hydrostatic chamber, within which an adjusted vacuum pressure maintains recovery operation under established hydrostatic relationships for a given set of dynamic flow conditions.