Belfast sink - joining old waste to new 40mm trap and pipe

[Basher]

The sink waste is 1 1/2"/40mm. The existing pipework is 32mm. Where would be the best place to use a reducer and what type of reducer?

Just to say that if you do go the 32mm route, putting this on the belfast sink instead of the T12A-F, solves that reduction issue:

BSP Coupling Waste Reducer - 1.5 inch

Medical, dental & commercial handwash taps & sinks including HTM64 taps & sinks. Tap spares & replacement parts for repairing most taps. Bathroom, kitchen & shower taps & accessories

www.notjusttaps.co.uk

 

[Plumb Line]

Just to say that if you do go the 32mm route, putting this on the belfast sink instead of the T12A-F, solves that reduction issue:

BSP Coupling Waste Reducer - 1.5 inch

Medical, dental & commercial handwash taps & sinks including HTM64 taps & sinks. Tap spares & replacement parts for repairing most taps. Bathroom, kitchen & shower taps & accessories

www.notjusttaps.co.uk

Good find! So that would solve both problems in one small piece - i.e. a flat wide washer for my awkwardly shaped waste, and a reduction to 32mm at the same time. In which case from there I'd need a 32mm telescopic P trap and that's it? Might just need to cut the existing pipe back a little if it sticks out too far for the P trap?

Seems a solution is hopefully coming together.

Shame my plumber couldn't have recommended any of this!

 

[ShaunCorbs]

Depends on what your planning on running the sink as will take a bit to drain in 32mm and glug abit

 

[Basher]

Depends on what your planning on running the sink as will take a bit to drain in 32mm and glug abit

I take the point, but the centre aperture in the original belfast waste fitting being used is much smaller than normal, probably around the 30mm mark, so that will throttle the flow as well!

 

[Plumb Line]

Depends on what your planning on running the sink as will take a bit to drain in 32mm and glug abit

The plan would be, from the sink plug hole:

• 1 1/2" - 1 1/4" coupler reducer with flat washer, as suggested by @Basher
• 32mm telescopic P trap
• Connect to existing pipework (which is 32mm) from there, as seen in this photo:

Is that likely to cause slow drain / glugging?

If using 40mm to prevent the slow drain / glugging, would everything have to be 40mm? Or would a 40mm trap going into the existing 32mm pipework be enough?

Cheers

EDIT:

I take the point, but the centre aperture in the original belfast waste fitting being used is much smaller than normal, probably around the 30mm mark, so that will throttle the flow as well!

I've just measured it and it's 34mm, so you weren't far off With that in mind, will 32 vs 40mm trap and pipes make much difference then?

 

[ShaunCorbs]

You’ve got nothing to loose other than a p trap and an adapter

 

[Plumb Line]

For the benefit of anyone coming across this in the future who finds themselves in a similar situation, my plan (as outlined in post #25) worked a treat, and I'm set up and all works perfectly.

Thanks one and all for the great help. I wouldn't have got there without you!