Our John Guest 5/16" QC X 1/4" Quick Connect Union Reducing Connector makes connecting water tubing easy.  The quick connections are simple, just put the tubing in and the connection is secure.  Push-fit technology makes sure the tubing stays put.  And with that easy connection, it's also easy to disconnect and replace without using tool.  These plastics have a high chemical resistance, and it's food grade quality that's suitable for water applications.  These are no to be used with gas, air compression, or vacuum applications.