Commercial waste pipe.

[SJB060685]

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.

 

[Burger]

I’m not sure it differs on commercial. I haven’t read the document, but have you tried this?

Approved Document H | Part H - Drainage and Waste Disposal | Planning Portal

 

[rpm]

Is the grease trap in the correct place and has it been serviced? Many aren`t on both points.

 

[Riley]

Was gonna say if there is no fat trap fit one

 

[Riley]

Stainless Steel Grease Trap 9KGB | Grease Traps UK

 

[SJB060685]

Where should this grease trap be installed. I don’t think there was one honestly. The whole run was about 30-40m with 7 wastes connecting and no sign of anything like that before it terminated outside.

 

[rpm]

Where should this grease trap be installed. I don’t think there was one honestly. The whole run was about 30-40m with 7 wastes connecting and no sign of anything like that before it terminated outside.

C`mon, read your words out loud, no point in putting it at the end of the pipe run is there, might even need more than one.

 

[SJB060685]

Lol, I didn’t think that through properly before talking did I. I’ve had a look at the PDF and there is nothing like that on the system at all. You’re right they probably need at least two based on what I saw today.

 

[ShaunCorbs]

depends on whats being fed into it them two of them big sinks (the normal washing / prep sinks) normally 50mm for 5 of them 110mm i would want

but the grease needs to be sorted else nothing will win eg grease trap on one or two and just use them two for grease only

 

[SJB060685]

Thanks for the useful and funny replies. Clearly plumbing is not my area of expertise lol. There is no grease traps installed anywhere and there’s one large prep sink, three wash basins and three washing machines.

 

[ShaunCorbs]

ideally 110mm but you will get some putting it in 50mm its the length thats the issue

 

[rpm]

If wash basin as in washing hands then where is the grease coming from as it shouldn`t be from the prep sink. Dishwashers anywhere?

 

[SJB060685]

This is what I was wondering rpm, the majority of fat was in a place only one of the wash basins was discharging through.

 

[rpm]

There was a large cafe in Oxford who had problems with grease building up over time so they had a connection at the start of the outlet pipe where once a month they hooked up a pressure jet washer and cleaned the pipe out because there was no room to install a grease trap. Crude but effective.

 

[SJB060685]

Unfortunately there isn’t really enough room to install a grease trap, despite the need. I will report back to him with all this information. Creating a cleaning port might be the only option for now

 

[king of pipes]

30 - 40m is crazy it will always block up even 50mm branches into a 110mm soil run that length will eventually have issues . kop

 

[SJB060685]

My concern is one wash basin is on a branch of about 15-20m, from what I’ve read this is way too long?

 

[king of pipes]

Way to long but it is what it is plenty of
rodding access points and the knowledge that from time to time there will be issues , or you address the problem and make major alterations to the drainage . Kop

 

[chris watkins]

My concern is one wash basin is on a branch of about 15-20m, from what I’ve read this is way too long?

Errr... if it is vented nothing is too long, just stop & think about it, 100mm below ground drains runs are often much longer.

What about using 75/82mm pipe if you think 50mm is to small?
It is all about how often the appliances discharge, for how long & what they are. The pipe shouldn't run more than 3/4 full but equally it needs to have, & maintain, a self cleaning velocity.
As the Romans found when building the grand aqueduct to feed Rome, not much new in this world !!

 

[Chuck]

they had a connection at the start of the outlet pipe where once a month they hooked up a pressure jet washer and cleaned the pipe out

Ah, yes... The old, "push it downstream and make it someone else's problem" approach...

 

[chris watkins]

Ah, yes... The old, "push it downstream and make it someone else's problem" approach...

If it is traced back to them they will be in trouble, it is take much more seriously now days.
Costing us a fortune to remove it, and them bl::::dy are wipes, if you want to wash it buy a Bidet.

 

[king of pipes]

My concern is one wash basin is on a branch of about 15-20m, from what I’ve read this is way too long?

Was advising on this post bud , a commercial kitchen should always have some sort of grease trap although plenty who don't especially in seaside town such as ours. kop

 

[SJB060685]

Thanks @chris watkins and @king of pipes. I appreciate your input, basically I just wanted to absorb your expertise and report back to him. To clarify further the wastes do not run into a stack with an external high level vent, or air admittance valve installed above highest flood point. It is simply many metres of 40mm before going through external wall and down into a gully, the only air admittance if you will is one tee with an upright piece of overflow pipe with a tube from a machine going into it. I’m right in thinking this not a vented system?

 

[chris watkins]

Yes it is a trap not an open vent.
Open vent pipe suitable terminated on the end of the run (last fitting connected) will stop it self siphoning all the traps connected. Albeit that gully on the end is trapped so no drain smells there will still be a stink from the pipework & if fitted it will not matter if it runs full bore. (might even need another half way)

 

[SJB060685]

Ok. That overflow did not have a trap on it though, it was simply an open ended pipe which could easily emit drain smells into the room.
So now you can picture the layout a bit better and know that the 40mm pipes do not enter any 100mm stack anywhere (just through wall and into gully) what should I suggest he has done? I’m not interested in this type of work personally so will strongly urge him to get a reputable plumber in who knows what he’s doing but I at least want to give him all the info he needs.
Thanks for your time Chris by the way