Nothing but metal piping should be used inside of a building, but in solid earth, starting from a point about 10 feet away from the cellar wall, we may use salt-glazed, vitrified, or terra cotta pipe for making the connection with the main sewer. This pipe is made in convenient lengths and shapes and is easily handled. Various fittings are made similar in form to those already described for cast iron. In laying tile pipe each piece should be carefully examined to see that it is smooth, round, and free from cracks. The ends should fit closely all around, and each length of pipe should fit into the next the full length of the hub. In making the joints nothing but the best hydraulic cement should be used, and great care should be taken that this is pressed well into the space between the two pipes. All cement that works through into the interior should be carefully removed by means of a swab or brush made especially for this purpose. The earth should be filled in around a pipe of this kind before the cement is set or else the joints are likely to crack. Fine soil should be filled in around the pipe to a depth of 3 or 4 inches, and rammed down solid, and the ditch may then be filled in without regard to the pipe. No tile pipe should be used inside of a house or nearer than about 10 feet for the reason it might not stand the pressure in case a stoppage should occur in the sewer. This kind of pipe is not intended to carry a pressure and when used in this way is seldom entirely filled with water. Joints between iron and tile piping are made with cement in the manner described for two sections of tile.