The push-pull technique involves pulling the old pipe out of the ground using pulling rods and special pulling/pushing heads, and simultaneously inserting a new ductile cast-iron pipe with BLS® socket joints and a cement-mortar coating into the same channel.
The nominal size of the pipe can be increased by multiple increments in this process. The single-channel push-pull technique is highly efficient, fast, reliable and economical.
The technique is used throughout the BWB supply area and in many areas of Switzerland and western Europe. In recent years, at least 20,000 m of ductile cast-iron pipes with BLS® joints and cement-mortar coatings have been installed using this procedure in Switzerland alone.
Auxiliary pipe technique
The auxiliary pipe technique is a spin-off of the push-pull technique. Instead of pulling a push-pull head into the channel, a steel auxiliary pipe is pushed into the pipe channel, forcing the old pipe out.
The next step is to join the auxiliary pipe to the new cast-iron pipe. By pulling the auxiliary pipe out, the engineers can slide the new cast-iron pipe into the same channel. This process is primarily used to replace steel pipes.
Berliner Wasserbetriebe (BWB), Berlin’s water supply and waste water disposal company, has replaced over 200,000 m of its pipeline network using this procedure since 2007. The majority of these pipes have been replaced with ductile cast-iron pipes with a cement-mortar coating and BLS® joints.