I'm not sure I understand the purpose of the gatorade bottle....

Are you cutting off the bottom of the Gatorade bottle, then placing the cut bottle over the end of the PVC pipe?  And then I would presume you remove the cap before pushing it down the hole?

or are you pushing the cap end of the Gatorade bottle into the end of the PVC pipe, and using the Gatorade bottle as kind of a plunger?  

I've had a similar idea.  However, my idea was to just push two PVC pipes down a groundhog hole, pour Ammonia in one pipe, and pour Bleach in the other pipe, and not have the complex fitting that you have.  

What you are doing is to get the two products mix before they hit any dirt.  My idea would mix the two products when the hit the dirt.  Two different ways to look at it.