to another a four inch 4 34 perforated polyvinylchloride drainpipe 38 is passed through the openings 36 in the end walls 28 30 and entirely through the peak of the gallery 10 an intermediate portion of the drainpipe is also suspended by a plastic suspension strap 56 having u clips 57 which engage a raised lip 58 of a one foot 1 39 in diameter inspection opening or pump out port 60 located in the top wall 14 of the main body portion 12 as best seen in fig5 a disk shaped cover 62 is used to allow access to the inspection opening 60 and also holds the suspension strap 56 in position the perforated drainpipe 38 is set at a proper pitch approximately between two inches 2 34 and four inches 4 34 per hundred foot 100 39 to achieve the desired effluent flow as shown in fig4 drainpipes 38 and 38a from adjoining galleries 10 and 10a can be joined by a junction pipe 64 so effluent can flow along the entire length of the drain field while the four inch 4 34 polyvinylchloride drainpipe is preferably extended through the entire ridge of the gallery units and held by the suspension straps alternatively small segments of polyvinylchloride drainpipe can merely extend between the openings in the ends of adjoining.