Why won't my birch beer carbonate?

Here's the deal, this is confusing the hell out of me:

I mixed up a 4gal batch of birch beer because I had a free tap and no beer ready to serve from it. It is my first attempt at soda ever. I made it from a bottle of soda flavoring, 4cups splenda, and 4cups sugar. I hooked it up to the same pressure as my fizzier ales (~18psi at ~38*F) and it has been over two weeks now. I have absolutely zero carbonation. I know that there is pressure in the keg because I can open the vent, serve it, etc, but the stuff just will not carbonate AT ALL. Anyone have any idea what is going on here?

Soda can seem flat even though it has 3/4 of it's carbonation in solution. You should be looking for at least 3.7-3.8 volumes of CO2, so at 38F, that would be about 24 psi.

I'll give that a shot when I get more gas ball lock connectors in next week. I'll be able to put all of my beers on one pressure and jack up the pressure on the soda. I'm tellin ya though, I get absolutely NO tingle on the tongue from this stuff right now.

I go over 30psi with my soda. Usually 40 to start for a couple days and then back down to 35 for serving.

Your 18 is half that and I would expect very little carb to be evident at that. There is almost nothing in the soda to retain the little co2 that you have so by the time it is in your glass any that was there is dissipated into the air. Also make sure you have a bunch of serving hose.

Is that an off-the shelf Birch Beer extract? I'd like to know what you think once it gets flowing to your satisfaction. I have been looking for a decent Birch Beer to do.

It is off the shelf, and I'll say this about it, it tastes half decent when it's flat. I could drink this on ice, maybe even in a mixed drink.

This was the brand, but birch instead of root beer. The website of the store where I got it says it is called "Rainbow Flavors":


Looks like you can get it here http://www.homebrewit.com/aisle/p/9105

Yep, that's the one they have at my HBS. I've been planning to try it out once I head back up there.

By the way, I had my cream soda just like I described above. 40 for 2 or 3 days then 35 for a few days, and I actually took the gas off of it to charge up a keg a few days back. I have pulled 5 or 6 full sodas off of the soda keg since then with no gas on it and it is still fully carbed.

I do sodas at 35 psi and use 20' of 3/16ths for the tap.