it s a bit late now but,
firstly, it would have been better to have tested the line before the final tie-in connections to whatever....there should a facility to use air vents at any high spots....
what kind of pipe is it ?
moving your pipe one inside the other would be unusual i"m not sure about that ...however for a lining, cement mortar lining of the internal wall of the pipe in-situ would be quite acceptable and suitable and indeed in the middle east quite usual...
in large dia cml pipe with posible man entry the lining can be knocked out and re-lined in-situ....unlined pipe can be cleaned and / or lined in- situ.....lining can be applied to new prior to welding , on site.
