When you see a spark in the switch i doubt it's quality. If your switch draws Sparks, a relay would certainly do to.
You can play it save and let the switch power a 5V or 12V line to activate a SolidStateRelay.. Most of this SSR's have a zero-detection-circuit so the initial current will not be too high. Thay also cost quite a bit less than a normal relay. And you don't have to take provisions to damp the relay's spike (a diode over the coil)
Sparks can also be eliminated, for a great deal, by bypassing the switch with a special capacitor.