we bought a house 3 years ago from a well known builders, a month ago the en-suite started leaking through the kitchen ceiling in more than one place. On investigation our plumber found the waste pipe was leaking on all joints as the welds had failed. The pipe was unsupported and flowed towards the toilet... I have approached the builder to fix but they say it’s nothing to do with them... my question is should a waste pipe drain to or away from toilet? Should a waste pipe be supported?