32 
BULLETIN 57, U. S. DEPARTMENT OF AGRICULTURE. 
FRESH AIQ 
INLET ■ 
conditions, such, as the water supply and the size of building. A safe 
rule is to allow a 35 or 40 gallon boiler to a building having one bath- 
room and to add 30 gallons additional capacity for every extra bath- 
room. One hundred square inches of water-back beating surface is 
sufficient for a 40-gallon boiler. 
Boilers should be galvanized inside and out, particularly inside- 
Copper boilers are preferable if properly coated inside with block tin. 
These are classed as 
light, heavy, and ex- 
tra heavy, the latter 
being tested to 150 
pounds water pres- 
sure. Ordinary steel 
or iron boilers are 
tested to 150 pounds 
water pressure and 
extra heavy ones to 
250 pounds pressure. 
The latter should be used when the gauge pressure is more than 40 
pounds per square inch. The following table gives standard sizes of 
galvanized boilers: 
Standard sizes of galvanized boilers. 
Fig. 26. — Sewer trap at house foundation, showing ventilator. 
Capacity. 
Length. 
Diameter. 
Capacity. 
Length. 
Diameter. 
Gallons. 
Feet. 
Inches. 
Gallons. 
Feet. 
Inches. 
IS 
3 
12 
4S 
6 
14 
21 
3£ 
12 
52 
5 
16 
24 
4 
12 
53 
4 
18 
24 
3 
14 
63 
6 
16 
27 
4| 
12 
66 
5 
18 
28 
3§ 
14 
79 
6 
18 
30 
O 
12 
S2 

20 
32 
4 
14 
98 
6 
20 
35 

13 
100 
5 
22 
36 
6 
12 
120 
6 
22 
36 
4| 
14 
120 
5 
94 
40 

14 
144 
6 
24 
42 
4 
16 
16S 
7 
24 
47 
ih 
16 
182 
s 
24 
SEWER PLUMBING. 
The sewer plumbing serves as a drain for the water plumbing. 
The drainage system should be so constructed as to carry away com- 
pletely everything emptied into it, and it should be constantly vented, 
frequently and thoroughly flushed, and have each of its openings into 
the house securely guarded. All drains, soil pipe, and waste pipe 
should be water-tight and air-tight. The soil pipe or house-drainage 
main begins at the sewer opening and passes up through the house 
as nearly vertical as possible and out through the roof for free venti- 
lation. It should be at least 4 inches in diameter, of extra heavy 
cast iron, and all joints should be tightly calked with lead and oakum. 
All discharge from the wash basins, sinks, and toilets empties into 
