HEATING BY HOT WATER. 171 
whether covered with a grating or not. Indeed, some- 
thing like 50 per cent. should be allowed in such cases. 
Pipes ought never to be buried in the soil, even partially, 
for where this is done they cannot radiate properly. 
Never bury iron pipes in ashes, the acid and sulphur 
they contain eating into the metal and quickly destroying 
them. 
ae =a 
(isi = f f 
Fig. 111. 
The Pipes and How to Fix Them.—As previously 
stated, hot-water pipes are cast in three sizes, viz., 2in., 
3in., and 4in. in diameter, internally. Pipes 5in. and 
6in. in diameter are occasionally used to a small extent, 
but chiefly for the connections, etc., of large apparatus. 
For any smaller sizes, or fittings, etc., than 2in., wrought- 
iron tubing, commonly known as “ gas-barrel,” is employed, 
Fig. 112. 
this also being made in several sizes, from jin. to 2in. 
in diameter, and fitted together by means of sockets and 
serew threads run on inside and outside. The 3in. and 
4in, pipes are usually cast in 9ft. lengths, and the 2in. 
size in 6ft. lengths, each with a socket on one end, as 
shown in Fig. 111. Any shorter or odd lengths are 
obtained by cutting, and when two blank or “spigot” 
