The middle of a frozen pipe should never be thawed first, because expansion of the water confined by ice on both sides may burst the pipe. When thawing a water pipe, work toward the supply, opening a faucet to show when the flow starts. When thawing a waste or sewer pipe, work upward from the lower end to permit the water to drain away.

Applying boiling water or hot cloths to a frozen pipe is simple and effective. Where there is no danger of fire a torch or burning news-paper run back and forth along the frozen pipe gives quick results. Underground or otherwise inaccessible pipes may be thawed as follows: Open the frozen water pipe on the house end. Insert one end of a small pipe or tube. With the aid of a funnel at the other end of the small pipe pour boiling water into it and push it forward as the ice melts. A piece of rubber tubing may be used to connect the funnel to the thaw pipe. Hold the funnel higher than the frozen pipe, so that the hot water has head and forces the cooled water back to the opening, where it may be caught in a pail. The head may be increased and the funnel may be more conveniently used if an elbow and a piece of vertical pipe are added to the outer end of the thaw pipe, as shown in figure 12. Add more thaw pipe at the outer end until a passage is made through the ice. Withdraw the thaw pipe quickly after the flow starts. Do not stop the flow until the thaw pipe is fully removed and the frozen pipe is cleared of ice. A small force pump is often used instead of a funnel and is much to be preferred for opening a long piece of pipe. If available, a jet of steam may be used instead of hot water; being hotter, it is more rapid.

Frozen traps and waste pipes are sometimes thawed by pouring in caustic soda or lye, obtainable at grocery stores for about 25 cents per pound. Chemicals of this character should be labeled "Poison" and should be kept where children cannot get them. To prevent freezing, the water in the traps of a vacant house should be removed during cold weather, and the traps should be filled with kerosene, crude glycerin, or a very strong brine made of common salt and water, or other substance mentioned in Farmers' Bulletin 1426, Farm Plumbing.