Hi guys. As some of you here know I don’t do plumbing work, 99% of my knowledge lies within oil fired heating so forgive me if this is a stupid question. I had to attend a commercial property today (close friends family run business). Complaint was wash basin wasn’t draining water away, easy enough, a blockage somewhere. There were no inspection ports for de-blocking etc etc on a 25m ish run and after making a couple cuts into waste pipe we found that the 40mm was severely blocked with grease and fat in several places. Anyway we’ve cleared what we can and had to redo some pipework as a couple swept tees had broken which we didn’t discover till half way through. My question is this, as it’s a commercial property what are the minimum waste sizes required for removal of water? In a house you have your standard 32mm and 40mm, this 25m run was 40mm and picked up several other waste connections along the way before discharging outside. With the amount of crap we found inside these pipes it made me think that larger waste pipes would not only get rid of the water quicker but more importantly not block up so quick. There was also a unit inline which slowly administered an anti grease forming solution, however this is clearly having no affect.