F., Denver, Colo., writes:

"I have had considerable trouble with the joint of a lead pipe connecting the water-back of a range and a kitchen boiler at the point where the lead pipe runs into the boiler. The joint is a wiped one, but I find that it leaks. What is the cause ?"

[The leak is caused by the unequal expansion or contraction of the three metals, the lead, solder, and copper, of your boiler when subjected to the changes of temperature of water in the boiler. The reason for this is that these metals do not expand equally for equal changes of temperature. The solder will thus have to conform to the changes in the other metals, and a disintegration of the joint will follow, the solder becoming granulated and cracked. Use a brass or copper pipe for the hot-water connection between the boiler and water-back.]