The method of making a caulked joint in a cast hot-water pipe is first to caulk the space about one-third full of hemp, then put about half an inch of putty, then a ring of hemp, then another ring of putty, and so on until full, finishing off with the putty. It must then be allowed sufficient time to harden before letting the water in, or the swelling of the first hemp will squeeze the lead back. Ordinary putty should not be mixed with white and red lead; the two latter ingredients only are used. Badly made and leaky joints cannot be remedied; they must be picked out and re-made as described above.