I noticed leak from my cellar wall. After digging a bit I managed to find leak coming from back of the compression nut of the elbow connector that connects to the 25 mm PVC under ground supply pipe. What could be the reason? Also there is not enough wriggle room to tighten or remove the connector. What is the best solution? pull the supply pipe forward - I am not sure if that could cause an issue further down under ground. Or should I take down more brick work more to expose the supply pipe - which could be a lot. I am complete newbie - Please all help is appreciated.

 

It doesn't look like you have to remove much more to get a pipe wrench on the connector. Rent a chipping gun if necessary,