Abstract: A valve assembly adapted to be coupled to the spigot of a conventional sink faucet, which valve can selectively divert water from the spigot to either an auxiliary filter or to a drain. The valve incorporates a housing having a threaded inlet, an internal chamber and first and second outlets. A slidably mounted spool defines a valve head, and normally directs the flow toward the drain, but the spool can be shifted to divert the flow to the filter on either a continuous or a "single-shot" basis.