Sounds like a good complement to your fiery arsenal. Depending on the tubing you used for the main parts, it gives you options if you pick up some adapter couplings - which you can stack in various ways if needed.
1/2 inch CPVC (beige pipe) is the narrowest at 5/8 inch outside diameter. A little 1/2 inch CPVC inline coupling is just big enough on the outside to fit snugly into a 1/2 inch PVC coupler so you can attach it to the latter size.
1/2 inch PVC (white pipe or gray conduit) is just under 7/8 inch OD - and there are lots of fittings available to transition it to just about any other size tubing.
1/2 inch PVC seems the most useful since it will fit inside the neck of a soda bottle without modification and make a fair seal (of course some duct tape can make it even better - or drill a hole in the bottle cap to closely fit the pipe).
Enjoy!
Yogi