Solution: Our technician arrived on site to jet slot drain and found slot was around 30% full of silt and stone. Jetted and cleared slot drain & sucked out the gully waste which was half full of silt and stone. The discharge was found to be blocked downstream, therefore we carried out extensive jetting downstream to around 100 meter distance but we were unable to clear line fully. Traced manholes around site to locate downstream manhole, found manhole next door on adjacent properly to be a possibility also trace to locate a large main line in the ground behind (possibly UU line). Further investigation required. We have taken a full load from site and tipped at disposal site, client issued the WTN. We have advised that a utility map is required if no current drainage plans are available. The client should speak to United Utilities to see if they have any assets running in the area or to determine ownership. Site left clean and tidy.