Big leak from compression (isolation valve's) onto plastic pipe. All done ok but used brass olive. 6mth later it poped off!!! yes insert was used etc etc..Amazing but not much damage from leak as we were in at the time...It was feeding a loft mounted shower digital mixer unit.. Plumber called around  to tell me I should have thrown away supplied brass and changed for copper as it compresses more!!! Wish i had known that before... !!