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Fitting a Belfast waste with a weir type overflow

Belfast with weir type overflow
Slotted waste
Belfast Sink overflow detail

A slotted waste, clearly showing the slot in the outlet.

Caution !! If you look at the slotted waste you may notice, that unlike any other waste,  waste water can run down the thread and cause a leak. This is why it is important to seal the thread  on a slotted waste and not just rely on the washer.


The easiest way to seal the thread is to run a full circle, bead of silicone around the thread before you spin on the nut and tighten it. Applying the bead nearer to the underside of the sink will reduce the chance of getting silicone over your hands.


Some sink fitters may prefer to use traditional plumber's putty instead of silicone to waterproof the waste.

To reduce the chances of leaks at the outlet please read below.

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If your Belfast sink has a "weir" type overflow like this. Then you will need a slotted waste outlet in order to collect the overflow water and to divert it down your waste pipe.