Dodgy - very dodgy, drainage under sink

[Robert Tyrrell]

Got called to a place yesterday that had a problem with the utility room sink waste backing up and leaking into the room.
When I examined it I could see why; there are two 40mm waste pipes, a drain from the dishwasher, and a drain from the washing machine - all feeding into one - yes one- 40mm pipe which then goes vertically into a rubber bung type of reducer that is under the sink cupboard.
The amount of water was causing syphonage, and noxious fumes, whist also causing the waste water to back up enough to push the bung up and allow the water to leak into the utility room.
All installed by a so called builder.
I told them to use one appliance at a time for now and when they return from their holiday I'll sort it out but how do builders get away with this? They do the work themselves, cutting a plumber out of the process and keeping the cash, and they make a complete hash of the job. Where were BC? Apparently they did't even come out to look at the extension when it was built.

Oh - I just remembered; The builder had used an overflow pipe stuck into the top of the 'Waste' stack in an attempt to elevate the siphonal problem - numpty.

I'm thinking of fitting a stub stack and connecting the four wastes properly.

Can anyone remember the water regs that covers the size of wastes and their associated drain size?

I can't remember and I'd like to quote it to the customer so they have something to get back to the builder with.

 

[Destroyer2813]

Don't see what your getting at with the two wastes going into one , a large amount of kitchen sinks have double spigot traps on with a dishwasher, washing machine and sink connected

 

[Destroyer2813]

The rubber bung is probably a mcalpine reducer, if it's backing up surely first thing is check for a blockege down the line

 

[Robert Tyrrell]

Cheers, forgot to say that I've been around the industry for a while now and I did clear the blockage but the crap plumbing still exist

 

[plumben]

Don't see what your getting at with the two wastes going into one , a large amount of kitchen sinks have double spigot traps on with a dishwasher, washing machine and sink connected

The double spigots are only designed for one appliance to be used at a time really though and struggle when theres more than one used in conjunction with pour plumbing

 

[Robert Tyrrell]

Don't see what your getting at with the two wastes going into one , a large amount of kitchen sinks have double spigot traps on with a dishwasher, washing machine and sink connected

Missed that post
I've just read my original post again and I should add that the two sink wastes are in addition to the two wastes from the washing machine and dishwasher. That makes four wastes exiting I to a 40mm pipe, which is the problem.

 

[Best]

Is the rubber bung reducer below the sink a 110mm x 40mm?
If it is an 110mm, then you can buy a 110mm with twin connections for using 2 waste pipes

 

[Geyser]

As best said. Or could change sink trap to double nozzle type and drop wastes into that. May need air admitance valve on 40mm.