=Sinks.=--The waste water from the kitchen is disposed of by means of sinks. Sinks are usually made of cast iron, painted, enameled, or galvanized. They are also made of wrought iron, as well as of earthenware and porcelain. Sinks must be set level, and provided with a strainer at the outlet to prevent large particles of kitchen refuse from being swept into the pipe and obstructing it. If possible the back and sides of a sink should be cast from one piece; the back and sides, when of wood, should be covered by nonabsorbent material, to prevent the wood from becoming saturated with waste water.[18] No woodwork should inclose sinks; they should be supported on iron legs and be open beneath and around. The trap of a sink is usually two inches in diameter, and should be near the sink; it should have a screw cap for cleaning and inspection, and the branch vent pipe should be at the crown of the trap. =Washbasins.=--Washbasins are placed in bathrooms, and, when properly constructed and fitted, are a source of comfort. They should not be located in bedrooms, and should be open, without any woodwork around them. The washbowls are made of porcelain or marble, with a socket at the outlet, into which a plug is fitted. =Wash Tubs.=--For laundry purposes wooden, iron-enameled, stone, and porcelain tubs are fitted in the kitchen or laundry room. Porcelain is the best material, although very expensive. The soapstone tub is the next best; it is clean, nonabsorbent, and not too expensive. Wood should never be used, as it soon becomes saturated, is foul, leaks, and is offensive. In old houses, wherever there are wooden tubs, they should be covered with zinc or some nonabsorbent material. The wash tubs are placed in pairs, sometimes three in a row, and they are generally connected with one lead waste pipe one and a half to two inches in diameter, with one trap for all the tubs. =Bath Tubs.=--Bath tubs are made of enameled iron or porcelain, and should not be covered or inclosed by any woodwork. The branch waste pipe should be trapped and connected with the main waste or soil pipe. The floor about the tub in the bathroom should be of nonabsorbent material.[19] =Refrigerators.=--The waste pipes of refrigerators should not connect with any of the house pipes, but should be emptied into a basin or pail; or, if the refrigerator is large, its waste pipe should be conducted to the cellar, where it should discharge into a properly trapped, sewer-connected and water-supplied open sink. =Boilers.=--The so-called sediment pipe from the hot-water boiler in the kitchen should be connected with the sink trap at the inlet side of the trap. =Urinals.=--As a rule, no urinals should be tolerated within a house; they are permissible only in factories and office buildings. The material is enameled iron or porcelain. They must be provided with a proper water supply to flush them.