They consist of a central ring with submerged bellows which go up and down with the movement of the water, and external floats which keep the ring level to the surface.

Weir skimmers are used in combination with an oil recovery pump, which can be on board the skimmer itself, or located on land. A major advantage of weir skimmers without on-board pumps is that they are very light and easy to deploy.

Weir skimmers work by the layer of oil on the water being sucked into the central ring (or weir), from where it is pumped away through oil transfer hoses.

Weir skimmers are used in cases where a simple and economical solution is required (with respect to their nominal recovery capacity) and where there is a thick layer of oil. By nature, weir skimmers are more efficient with low viscosity oils.