HO USE-BRAINA GE. 319 



affecting the comfort and health, of the community generally than 

 it is to the individual householder. 



6. The incasing of fixtures in wood should be avoided as far 

 as possible. The best bath-tubs and wash-basins are those in 

 which the overflow is through a stand-pipe which is lifted to dis- 

 charge the water, thus avoiding side or end overflows. The best 

 closets are wash-out, short-hopper or siphon-jet closets. Every 

 closet should have its own cistern, and the flushing-pii)e from the 

 cistern should be not less than one and a half inch in diameter. 

 Housemaids' sinks should have a flushing rim and a separate 

 cistern. Fixed laundry-tubs should never be made of wood. 

 Urinals in a private house are usually an unnecessary nuisance ; 

 if put in, they must be cleansed frequently by rubbing. It is 

 better that fixtures should be opposite windows than against 

 outer walls, to avoid dark places beneath and around them, and 

 to prevent danger of freezing the pipes. 



7. To prevent the passage of soil-pipe and sewer gases, with 

 their suspended micro-organisms, through the fixtures into the 

 house, some form of trap must be used, and this should always be 

 placed as close as x>ossible to the fixture which it is to guard. 

 The best form of trap under all ordinary circumstances is a water- 

 trap made by a bend in the pipe, forming what are known to all 

 plumbers as S or half-S traps. Such a trap, so long as it pre- 

 serves its water-seal, affords ample protection against both gases 

 and bacteria, and, in ordinary dwelling-houses, it is easily pro- 

 tected against the loss of its seal by evaporation or by siphonage. 

 If a fixture remains unused for several months, its trap will be- 

 come unsealed by evaporation. In the trap to the outlet-pipe 

 from an ordinary wash-basin this will occur in about two months 

 if the trap is not ventilated, and in about two weeks if it is venti- 

 lated. This will be referred to again in speaking of the care of 

 house-drainage. As regards siphonage, the proper ventilation of 

 the traps is a sufficient protection in all ordinary habitations of 

 three or four stories. The ventilation of traps is not, however, 

 solely for the prevention of siphonage ; it is of equal if not 

 greater importance to secure a current of air through all parts of 

 the pipes so as to promote the constant oxidation and removal of 

 the slime which lines all pipes devoted to house-drainage. The 

 immediate agents which produce this oxidation or slow burning 

 of the organic matter which smears the interior of the pipes are 

 those bacteria which are called aerobic, because they flourish best 

 where there is plenty of oxygen. These are Nature's scavengers ; 

 the great majority of them are not dangerous to health, but rather 

 tend to destroy or starve out the really dangerous specific forms. 

 They convert the soil-pipe slime into gases and soluble products, 

 which products are washed away by the next flush of water ; and 



