An automated slide stainer with slides mounted in a horizontal position on a rotary carousel. Reagents and rinse liquids are automatically dispensed onto tissue sections or cells mounted on slides for the purpose of performing chemical or immunohistochemical stains. The rinse liquids are removed by an aspiration head connected to a source of vacuum. The aspiration head is a hollow chamber with a flattened bottom aspect. Eight holes in the bottom of the aspiration head provide for fluid communication between the exterior and interior of the aspiration head. To aspirate liquid off of a slide, the aspiration head is lowered so that the bottom aspect contacts the liquid. The liquid is sucked into the hollow interior of the aspiration head and collected into a liquid waste collection bottle. Several different liquid waste collection bottles are placed in parallel, between the source of vacuum and the aspiration head. A solenoid valve is positioned in line with each liquid waste collection bottle. Depending upon which solenoid valve is opened, the operator can direct the liquid waste to be collected into a specified liquid waste collection bottle.