New pipe-crawling robots in use in the UK can patch broken pipes from inside, without tearing up the streets:
First the bag is positioned at the point where damage has occurred and is inflated until it fits the pipe and irons out any dents.
Steam is then pumped in to glue the new lining to the walls of the pipe, which usually takes around two hours.
By using ultra-violet light to dry the glue this fix time has been cut to just 30 minutes.
Sharp objects or obstructions which cannot be removed with the bag are dealt with using remotely-operated high-pressure water jets.
(via Futurismic)