Abstract: A water filter adapter including a manifold defining an inlet port configured to couple with an output of a water filter module and an outlet port configured to couple with an input connection of a system, for example a water tank of an RV or boat. The water filter adapter further includes a shutoff valve assembly positioned between the inlet port and the outlet port for controlling the flow of water at the input connection of the system rather than an external water source, such as campsite hook-ups or marina connections. In a preferred embodiment the outlet port is offset about ninety degrees from the inlet port to minimize the flow path post-filtration as much as possible while still facilitating a secure connection between the water filter adapter and the input connection of the system and between the water filter adapter and the water filter module.