GROUND-WATER REACHING SEWERS 147 



the amount of ground-water entering may be restricted to that 

 due to the porosity of the brick and mortar. Various methods 

 are found in pocket-books for making brick walls impervious, 

 and many statements are made to the effect that brick masonry 

 in engineering construction allows considerable water to pass 

 through. No definite data, however, seem available for the 

 exact amount of such percolation under different conditions of 

 construction. In the case of sewers, experience seems to show 

 that in the same ground more water comes through a brick 

 than through a pipe sewer; but nothing definite is known on 

 the subject. 



The author has seen water under a head of a few feet pass, 

 in numberless small streams, through a 1 2-inch brick wall. 

 He has experimented with tanks of brickwork, with 8-inch 

 walls, with and without plaster coats, and is convinced that, 

 with the work of ordinary housemasons, it is beyond all reason 

 to expect an 8-inch brick wall to be water-tight, even with 

 an ordinary plaster coat. It is essential for water-tightness 

 that the voids of the plaster coat be filled either with several 

 coats of cement wash, with asphalt, or with some one of the 

 many water-proofing paints or plasters available. Mr. John 

 N. Brooks * has suggested that a more suitable unit for infiltra- 

 tion for brick or concrete sewers is gallons per day per square 

 yard of interior surface, and from some experiments of his 

 own on a concrete sewer 9 miles long, he finds the leakage 

 for 4- to 6-foot sewers, in firs t-classl condition with special 

 waterproofing of three-ply felt and pitch, to be at the rate of 

 0.8 gallon per square yard, or 6000 gallons per mile for the 

 4-foot sewer. 



The only two instances on record of leakage through the 

 walls of brick sewers, are at Orange, N. J., and at Maiden, 

 Mass., already referred to, and instanced by Mr. A. P. Folwell,f 

 secretary of the American Society of Municipal Improvements. 

 The leakage was found to be at the rates of 570,000 and 800,000 



*Proc. Am. Soc. C. E., Vol. XXVIII, p. 1705. 

 f Municipal Engineering, Vol. XXV, p. 348. 



