Sealing sanitary and storm sewer piping is typically more difficult than sealing interior plumbing, mostly because of their construction, and typically because of their size. This is especially true in main lines. In a typical sewer main, the pipe ends are spigot-and-bell construction, and sealing is commonly achieved with some type of o-ring. There are numerous inherent problems with assembling these connections.
Initially, there is the problem that pipe ends may not have been designed and manufactured with grooves to receive the sealing o-ring. Then there is the situation that when there is a groove, it may not necessarily be the desired depth, or even if it is that it just requires more material in the seal to fill that groove. In all instances, there is the common danger of rolling the seal out of position or shearing part of it completely away; leaks can and do result.