Can you offer any further detail on what is meant by "flexible filler" as shown on standard detail W6 - Air Valve Assembly (25mm & 50mm valves)?

Standard drawing W6 section AA shows a 50 mm gap between the pipe and the precast concrete barrel, with a “flexible filler”. The cross reference spec 33 11 01 Waterworks cross references Section 33 44 01 Manholes and Catch-basins, but there is no specific MMCD standard for flexible joint fillers in the material specifications.

However, a brief Internet search turned up the following: ASTM C990, “Standard Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections Using Preformed Flexible Joint Sealants” Covers both bitumen and butyl sealants. • Provides a flexible, watertight joint. • Maintains both adhesion and cohesion between sections. • Conforms to a wide variety of joint geometry and can fill slight imperfections. • Maintains seal even if settlement occurs. This specification covers joints for precast concrete pipe and box, and other sections using preformed flexible joint sealants for use in storm sewers and culverts which are not intended to operate under internal pressure, or are not subject to infiltration or exfiltration limits. Joint material used in horizontal applications is intended to prevent the flow of solids through the joint. ASTM C923, “Standard Specification for Resilient Connectors Between Reinforced Concrete Manhole Structures, Pipes, and Laterals" Designed to minimize leakage between the pipe and manhole. • Primarily used in sanitary sewer applications.

There are a number of video resources for pipe gasket installations for manholes and pipe joints. You might want to check out http://www.press-seal.com/videos/