The following link is to various topics about mouth-taping and other devices to try to control mouth air leaks.
I give credit to our own Rested Gal for compiling these.  They may be of help to you in dealing with your mouth breathing problems.

Links to: Mouth leaks - Air Leaks - Tape - DIY Guard


Linda

Hi Linda,
       I'm experimenting with a way to limit the amount of mouth breathing, not block it. I've tried full face masks, the best one so far is the Probasics zzz-mask. It's, light seals great even with my beard and cheap, $89.00 on cpapsupply.com. I just have a problem exhaleing and can't afford a new cpap machine.
        The idea is to make a device to cover the mouth that allows a bit of breathing but not enough to dump the pressure from the cpap. My pressure is set to 11.0. I remember as a kid having a knit scarf over my mouth on zero degree days. I'd end up breathing through my mouth while running around and remember the warm moist sensation while breathing through my scarf. I thought about trying an ear head band sold in stores but they would be too much work cleaning all the time. I just got a call from my mask technician and she suggested a hospital germ mask that is flat and you could layer them until the right amount of restriction to seal or reduce the mouth breathing, then toss it because it's disposable. This would allow a mouth breather to use the mirage swift nasal pillow interface which is my favorite for compliance. If only I could keep my mouth shut! If anyone has an idea for a mouth breather blocker other than tape or internal mouth device I 'd love to hear the idea.
                                                                                                   Thanks for all the online help you post,
                                                                                                                                                            Baxter