Although the popularity of the waste disposal unit increased in the 1970's, only in very few countries (for example the USA) are they really commonplace in the kitchen. Currently in the UK less than 25% of households have one fitted.
The unit is usually fitted in a cupboard under the sink, and is designed to grind soft food waste, such as potato peel, left over vegetables, etc, into a pulp which can then be washed away into the sewers. Often, when a new kitchen is being fitted, a separate bowl will be fitted for washing vegetables etc, and having a suitable hole (usually 89mm) in the bottom to which the waste disposal unit can be connected. Alternatively, a special cutter can be bought or hired to cut a hole into an existing standard sink. The unit is then installed between the sink outlet and the waste pipe.
They fall into two basic categories, continuous feed and batch feed, but both operate in essentially similar ways. Waste is fed into the unit, where a rotating steel cutting blade driven by an electric motor chops the waste into tiny pieces. These mix with the water resulting in a slurry which goes into the sewer in the same way as normal waste water. With a continuous feed model the unit is switched on with a manual switch, then the tap is turned on and the food scraps are fed in. With batch feed, the unit normally requires a plug to be inserted into the sink waste outlet to prevent it being switched on accidentally.
A very useful addition to the kitchen, the waste disposal unit may, by the turn of the century, become as commonplace as the automatic washing machine.
