A gate valve includes a valve body having a fluid passage for the passage of liquid, sludge and/or fecal matter and a substantially flat slider. The slider is slideable between an opened and a closed position in order to open or block the fluid passage, respectively. The slider includes two opposite straight edges via which the slider is slidably guided in the valve body surrounding it. The slider is substantially made from a plastic material. The slider includes flanges along each of the two opposite straight edges for providing rigidity to the slider.
