If you don't run ozone, just cap the ozone port off at the pump. The ozone port should only draw air in if ozone is being used. In the absence of ozone, that port should be capped off. You can get a package plastic vacuum port plugs at the auto parts store like Pep Boys that will include a size that will slip over the port on the pump to plug it off. They usually include a few different colors and are typically in the "Help" section. Some of the Alpha's included a port cover while others didn't. The port cover insures that the volute is what is drawing the air in via the silencer instead of also through the ozone port.
