Hidden overflow ditch device and mounting method

The invention relates to a concealed overflow ditch device and a mounting method, and belongs to a rainwater utilization device, the concealed overflow ditch device comprises one or more adapter sections, desilting drainage tanks matched with the adapter sections in section number and an overflow ditch formed by splicing a plurality of standard pipe sections, and the adapter sections are connected with the desilting drainage tanks in parallel; the adapter pipe section and the standard pipe sections are connected in series through a connecting clamping plate which is arranged at a pipe opening and is of a channel steel structure; a row of adapter pipe overflow holes are formed in the upper part of the front surface of the adapter pipe section, and large drainage long holes are formed below the adapter pipe overflow holes; a water inlet long hole corresponding to the drainage large long hole is formed in the upper portion of the back face of the desilting drainage box, the lower portion of the desilting drainag