ErtelAlsop’s externally ported filters are ErtelAlsop’s externally ported filters are designed for small to medium sized wineries, breweries, distilleries, and the food and beverage market in general. The BW line includes stainless steel valves (1 inch BSP), inlet and outlet sight glass, and 40 x 40 cm food-grade Noryl plastic plates which are steam sterilizable. A dividing head is also an option, which allows for 2-stage (double) filtration. Double filtration allows for your product to pass through a coarse filter media, and then also through a polishing filter media while passing through the press only once. Not only does this save you time, but it also reduces the amount of product agitation and handling.