A coupling system for interconnecting a tube to a valve body is provided. The valve body has a body portion and a nipple extending from the body portion, and the nipple has a threaded external surface and an internal wall defining a bore. The coupling system further includes an adapter having opposing first and second ends, a nut defining a hole through which the first end passes, and a compression fitting located between the nipple, the adapter, and the nut such that when the nut is tightened onto the nipple, the compression fitting inhibits removal of the adapter from the valve body. The adapter defines a passageway extending from the first end to the second end, wherein the first end is received in the bore and the second end is configured to couple to the tube. The nut has an internally threaded surface configured to engage the threaded external surface.