Pipe Connection to the Manhole
The relatively high thermal elasticity of the PE material causes significant changes in the pipe length; one inch change in length per 100 ft of pipe for each 10ºF temperature change. Therefore, in extreme hot or cold weather when there is significant difference between the temperature of the deep soil and the ambient air temperature, it is recommended to allow the pipe to rest for 12 to 24 hours prior to installing tie-ins. Similarly, when pipe has been pulled to a significant portion of its allowable tensile load, it may be prudent to let the pipe rest before connecting to other pipes, fittings, manholes, and laterals. This procedure allows the pipe to rebound from any stretch that may have occurred during bursting.
In most pipe bursting applications, the sewer line is old and deteriorated, as well as the manholes along the line. In most cases, it is economical, on a life-cycle basis, to replace the old deteriorated manholes and use their location as pulling or insertion shafts. When existing manholes are replaced with new ones, connections to PE pipe can be made using flexible rubber manhole connectors, or "boots." A pipe clamp is used to tighten the boot around the PE pipe as shown below.
Connecting PE Pipe to New Concrete Manhole
Connecting PE Pipe to Old Manhole
If the old manhole is in acceptable condition and it is reasonable to re-use it after bursting, the manhole benching is removed and the pipe opening is enlarged to allow the passage of the bursting head. Expandable urethane grout and oakum can be used to create a seal between the existing pipe opening and the PE pipe, as shown in figure above. The compression allows pipe movement.
Frequently, the inlets and outlets of the manhole are modified for the bursting for the bursting operation, or otherwise affected, and the resulting inlet or outlet is no longer round. A low shrink polymer cement grout may be used to repair the damage. To obtain a good seal to the PE pipe, a special PVC fitting with a bell end coated with sand at the outer surface is used, as shown in the figure below. The grout bonds to the manhole and the rough sandy surface of the PVC fitting. A gasket between the PVC fitting and the PE pipe allows the PE pipe to move if expansion or contraction occurs. The PVC fitting is intended for PE pipes of SDR 21 or lower.
Connecting PE Pipe to Old Manhole with Damaged Inlets/Outlet