most of us older plumbers are not grumpy more dismade with the falling standerds in the plumbing industry,good training is allways worth while,but over the last few years i have had to inspect and rectify many unvented systems,i to have to register with bpec and go every 4 years to requalify ,with the course format there is no way anyone could fail this course.and if you can read the manufactors instructions there is no way it should be put in incorectly,but they are.so why ,is it dont care?cant be botherd ? cant read?