came accross a new build/2nd owner about 5 years old.
she just moved in and wanted the dishwasher plumbing in 1&1/2 m away from allocated position on a return wall.
did the new run andd the connecting joint leaked as pipe was not compatible so bunged on a compression waste, sorted!!
i then took a look down back of units and saw the next joint down was leaking!!
long story short 4 lengths of waste with 4-5 joints had all diffrent pipe makes. when i took them all out and looked at them i was dumbfounded the 'builders' had used so many off-cuts and just slapped them in. poor woman from a £70 job ended up £240 lighter & kitchen re-fit before the kettle got unpacked