Leaky basin trap - advice needed!

[PlumbBobBob]

hire a professional what?

 

[kimbo]

This is what you want I get the same trouble and this works a treat it has a short thread to go on to the metal waste and a long thread to go onto the trap. Silicone in my book is only a last resort and looks like a bodge.
Mcalpine Multifit Waste Pipe Fittings - MCALPINE S12AF 1.1/4" M+F FLUSHWASTE EXTENSION - R J Pryce - Plumbing, Builders Merchant & Ironmongery
Trap extension

 

[SimonG]

Tool station do something similar in 1", 2" and 3" lengths for 1 1/4" and 1 1/2". Used them a few times and found them to do the job.