Apparatus and methods for distributing gases into a processing chamber are disclosed. In one embodiment, the apparatus includes a gas distribution plate having a plurality of apertures disposed therethrough and a blocker plate having both a plurality of apertures disposed therethrough and a plurality of feed through passageways disposed therein. A first gas pathway delivers a first gas through the plurality of apertures in the blocker plate and the gas distribution plate. A bypass gas pathway delivers a second gas through the plurality of feed through passageways in the blocker plate and to areas around the blocker plate prior to the second gas passing through the gas distribution plate.