Checking carbonation of keg- natural carbing

I kegged my first beer over the weekend. Man, was that easy. I'm already starting to look into converting everything to kegging, even on stuff I'm going to bottle (ala the BMBF).

Right now though, I have one of those picnic taps with co2 cartridges for dispensing. I'm pretty sure I seated the lid and purged it properly, but my overwhelming fear is that I'm going to tap the keg, and the beer will be flat.

Is there any way for me to check and make sure the beer is carbonating without a gauge? Would soapy water on the lid work?

It's way too early to check it yet (give it a couple more weeks) but at that point just attach your picnic faucet and pull a small sample.

If you used keg lube and got a good seal, you shouldn't need to worry.

I'm assuming you primed the beer with corn sugar before kegging.

The simple method for checking that carbonation is taking place is to wait 3 weeks and then give the relief valve a very quick pull.

That hiss you hear will tell you your beer is carbing just fine.

There's even enough pressure by this time to push a sample for tasting without wasting a cartridge.

The key is to treat that keg like a bottle and leave it alone at 70 degrees for 21 days.