This page contains information about selecting and using brew kettles.
There are various advantages for choosing one metal over another. The most common metals for kettles are stainless steel and aluminum.
For metal comparison, see the metallurgy page.
For extract brewing:
For Brew In A Bag (BIAB):
Available in weldless or welded versions, valves are often attached near the bottom of the kettle to allow easy transfer of wort after the boil. A hole is drilled in the kettle and a ball valve is attached. Welded valves are more durable and less prone to leaking, but weldless valves must be used on non-weldable metals such as aluminum.
After boiling, tubing can be connected to the valve and run to a wort chiller or directly to a fermenter. This is often easier than starting a siphon, and the valve can additionally have a filter to prevent trub from exiting the kettle.
Valves often have a diptube attached that extend lower than the opening in the kettle so drain wort that is lower than the height of the valve. The diptube can be a solid piece of pipe, or a mesh braid to filter solids. Mesh braids can be easily clogged by the fine particulate cause by pellet hops, but are effective at filtering the sediment from whole leaf hops.
The alternative to using a valve drain is simply siphoning from the top of the kettle, often assisted by a racking cane.