The invention discloses a pre-positioned filter cleaning method. The method comprises the following steps: a draining turn button is rotated with an angle being 90 DEG, a draining valve at a lower part is opened, a state is kept for 30 seconds, positive flushing is carried out, after flushing is completed, the draining turn button is rotated with the angle being 90 DEG C, and a normal water-usagestate is recovered. Compared with the prior art, a pre-positioned filter is mainly composed of a high-quality
carbon steel cylindrical shell, a stainless steel wedge-type filter screen, a
butterfly valve and a
pollution-
discharge apparatus. when the pre-positioned filter operates, the
butterfly valve is in an opening state, water flows into the pre-positioned filter through an inlet, and is filtered through the filter screen and then flows to an outlet, and the
dirt in water is intercepted by the filter screen. when the pre-positioned filter requires
pollution discharge, the
butterfly valve isclosed, a
pollution-
discharge valve is opened, the water is subjected to front half way filtering, a part of water directly flows into a
human system, the other part of the water flows by the filterscreen from outside to inside, and is discharged through a
sewage draining port. The effect of automatic flushing with a reverse direction of the filter screen and discharge of the impurities can be realized. A whole reverse-flushing pollution discharge process does not require closure of the
system, and the on-line pollution discharge is realized.