cracking. Soldered connections Solder fittings are smooth, and easily slip onto the end of a tubing section. Both the male and female ends of the pipe or pipe connectors are cleaned thoroughly then coated with flux to make sure there is no surface oxide and to ensure that the solder will bond properly with the base metal. The joint is then heated using a torch, and solder is melted into the connection. When the solder cools, it forms a very strong bond which can last for decades. Solder-connected rigid copper is the most popular choice for water supply lines in modern buildings. In situations where many connections must be made at once (such as plumbing of a new building), solder offers much quicker and much less expensive joinery than compression or flare fittings. The term sweating is sometimes used to describe the process of soldering pipes. Compression connections Compression fittings use a soft metal or thermoplastic ring (the compression ring or "ferrule") which is squeezed onto the pipe and into the fitting by a compression nut. The soft metal conforms to the surface of the tubing and the fitting, and creates a seal. Compression connections do not typically have the long life that sweat connections offer, but are advantageous in many cases because they are easy to make using basic tools. A disadvantage in compression connections is that they take longer to make than sweat, and sometimes require retightening over time to stop leaks. Crimped or pressed connections Crimped or pressed connections use special copper fittings which are permanently attached to rigid copper tubing with a powered crimper. The special fittings, manufactured with sealant already inside, slide over the tubing to be connected. Thousands of pounds-force per square inch of pressure are used to deform the fitting and compress the sealant against the inner copper tubing, creating a watertight seal. Advantages of this method are: A correctly crimped connection should last as long as the tubing. It takes less time to complete than other methods. It is cleaner in both appearance and the materials used to make the connection. No open flame is used during the connection process. Disadvantages are: The fittings used are harder to find and cost significantly more than sweat type fittings. The fittings are not re-usable. If a design change is required or if a joint is found to be defective or improperly crimped, the already