Sink Installation

The mount decides the job

How a sink attaches determines almost everything else, and it is worth establishing before anything is bought.

Drop-in. Sits on the worktop with its rim over the cut edge. Forgiving, because the rim hides the cut and the seal is easy to make.

Undermount. Fixes beneath the worktop, so the cut edge is visible and has to be finished. It cannot simply replace a drop-in in the same opening.

Farmhouse. The front face is exposed and the cabinet itself usually needs modifying to take it.

Going from drop-in to undermount is worktop work. The other way round is usually straightforward. Knowing which you are doing changes who else needs to be involved.

Underneath, build for where the waste actually is

The trap arrangement is where installations quietly go wrong.

A new sink almost never puts its outlet exactly where the old one was. A deeper bowl, a double instead of a single, or a disposal added underneath all move it.

The correct response is to build the trap to suit the new position. The common shortcut is to stretch and angle the existing pipework until it reaches, which produces strained joints and, more damagingly, the wrong fall.

A waste run that does not fall properly drains slowly and holds water, permanently, for as long as the sink is there. It is worth doing once rather than living with.