Pipe sweating is a term that is used to mean a couple of different things. When hearing the term, the layperson may think of the fact that a glass of cold liquid "sweats" when it’s hot outside. Pipe sweating can mean the same thing, except with pipes. This type of pipe sweating happens because of humidity – the cool pipes attract the humidity in the air and cause condensation to form on the exterior of the pipes.

This type of pipe sweating can be easily remedied. One method is to reduce the humidity in the air. Dehumidifiers are available to do just this; you can set one up in the basement or wherever you have the problem.

Another method of reducing pipe sweating is to insulate the pipes. Foam tube insulation is available for this purpose at most hardware stores. Simply measure the pipes and cut the tube insulation to the right size. The insulation has a slit all the way down one side, so that you can fit it around the pipes without having to disconnect anything.

In a phenomenon similar to this type of pipe sweating, sometimes the outside of a toilet tank can sweat as well. Although insulation can be used to reduce such sweating – like with pipe sweating, except this time the insulation goes on the inside of the tank – another method is to install an anti-sweat valve. The valve mixes a little hot water with the water in the tank, keeping it from getting cold enough to cause the tank to sweat.

For a plumber, however, pipe sweating has an entirely different meaning. Pipe sweating is a trade term for soldering pipes together. This type of pipe sweating is performed with a propane torch. The copper pipes to be joined are heated at the juncture point, and then solder – a metal compound that is heated and used like glue between the two pipes – is applied. Pipe sweating can be a tricky venture for beginners, and it often takes a little while for a novice to get the feel of it.