Wet taps (also known as hot taps or pressure taps) add a branch line to an existing pipe of the same size or larger. This operation consists of welding in a thread-o-let or flanged pipe spool on to the existing pipe. Or a saddle can be bolted around the pipe. Next a valve is installed. The entire assembly is pressure tested. The tapping machine attaches to the valve and drills through the valve into the existing main. The drill is withdrawn through the valve, the valve closes, and the tapping machine is removed. The completed work ends with a valve installed on the existing main, ready for any piping connections.