Waste water fittings for metal sinks

Modern metal (mainly stainless steel) sinks come without an integral overflow however some old (probably imperial sized) sinks did have a built in overflow, as such, the waste water installation is fairly similar to that shown for hand basins.

This page deals with sinks where there is no integral overflow, just a hole.

To save working in confined areas, it is usually a good idea to fit the waste fittings (excluding the trap) before the sink is fitted into position.

Modern sink waste fittings are fairly standard although there are a number of options to choose for the plug hole fitting - there's nothing really to choose between them, they are just different.

NOTE: On all the wastes shown, a washer is indicated under the sink outlet inside the sink, if the kit purchased is not supplied with one, spread some plumbers sealant (Plumbers Mate or similar) under the rim of the outlet before inserting, wipe off any excess from inside the sink once the outlet has been tightened.

The sink waste overflow is normally straight forward, the overflow grille on the inside of the sink is screwed into the overflow which is connected to a flexible downpipe to the sink waste trap. To tighten it may help to carefully push the jaws of a pair of long nosed pliers into the grille to get something to hold - but do not use too much force as the fitting is often plastic and liable to damage. A washer is normally fitted between the grille and the sink surface to provide a water seal.

Probably the easiest fitting for the sink outlet is the adapter under the sink. This fitting is held in place by a screw through the centre of the grille into a captive nut in the centre of the adapter. The screw needs to be tightened to compress the washers to give a watertight seal. Washers are normally placed under the grille in the sink and between the adapter and the underside of the sink. The adapter incorporates an inlet for the flexible pipe from the sink overflow. The illustration to the right shows a bottle trap fitted whereas the illustration below shows a 'P' traps. The traps are actually completely interchangeable in the applications - even an 'S' trap could be used - the type fitted may depend upon personal preference, space available under the sink or the waste water pipe run direction.

An alternative fitting for the sink waste uses a deep plug hole fitting, with slots in opposite sides to accept the waste from the overflow, and a long threaded body. The banjo from the overflow fits over the plug hole fitting and both are secured by a large nut fitted against the underside of the banjo. Before fitting the large nut, apply Plumbers Mate to the screw thread on the outlet. Fit the nut so that it traps the Plumbers Mate in the thread and tighten. The nut needs to be tightened using a spanner or stilsons to compress the washers to give a watertight seal. Washers are normally placed under the plug hole in the sink and between the banjo and the underside of the sink.

Another alternative is to use a short sink outlet fitting which is secured to the sink by a nut underneath while the overflow waste pipe goes to an inlet in the actual waste trap. The nut needs to be tightened using a spanner or stilsons to compress the washers to give a watertight seal. Washers are normally placed under the fitting in the sink and between the nut and the underside of the sink.