CONCRETE PIPE Maximum Allowable Openings Large Diameter Manholes When examining the structural integrity of a manhole section, there are two important considerations regarding pipe connections; the pipe diameter and the distance between openings. When multiple pipe penetrations are located nearby, the walls of the manhole structure are weakened. A concrete pipe placed within the manhole will act to reinforce the opening, while a plastic pipe, conversely, will be limited in its ability to increase the structure’s strength, and as a result, additional reinforcement and engineering consideration may be required. The following section provides Lafarge’s recommendations for maximum allowable openings in large diameter manholes. Quick Reference 900 900 Maximum Recommended Opening Sizes Manhole Nominal Diameter1 1200 1350 1500 1650 1800 1950 2100 2400 2700 3000 1Bold Recommended Maximum Allowable Pipe Size (Straight Through and Dead End Configurations Only) Concrete 6002 675 750 750 9003 1050 1200 1500 1500 18004 Opening Provided 902 991 1080 1080 1288 1435 1613 1969 1969 2324 Plastic 6002 675 675 675 675 675 750 750 900 1200 Opening Provided 600 775 775 775 775 775 850 850 1000 1300 Edmonton Only 1800 1800 1350 1350 text indicates manhole diameters not available in Edmonton. Bold and italicized text indicates manhole diameters not available in Winnipeg. 2Maximum 525 mm diameter in Winnipeg. 31050 mm Concrete Pipe can be accommodated in a “dead end” manhole. 41950 mm Concrete Pipe can be accommodated in Edmonton only. PAGE 44 LAFARGE PIPE eMANUAL