Are the guys you’ve got in actually plumbers
It wouldn't surprise me if they were fully qualified these days to be honest.
I went to a job not that long ago and the customer said I was the fifth!!!!
Ridiculous!
It was something that any Engineer worth his / her salt would have diagnosed within 5 min too. That is the largest procession of Plumbers I have heard of but it is by no means the only time I've heard it.
They even left tools!!!
The mind boggles.