Finding a CO2 Leak in your system.

The past few batches of brew i have been churning out into my kegs have been great. However after a few days of carbing with my 5lb CO2 tank into my Korney Kegs I notice all of my gas has leaked out. Usually when im putting the gas on I use a spray bottle with sudsy water and spray around all connections to see if there is a tiny leak however it seems as though I never find one. But it never fails when I check on the finished product there is no gas left. Its getting expensive at $18 a pop to fill this bad bear up. Does anyone have any suggestions on how I might go about finding leaks in a more efficient manner and what should be done about "tightening" the whole system down to ensure that my gas goes where it needs to....please help! I have 30 gallons of beer I need to carb up and no gas to do it with as of now......probably wont be able to fill till Monday which puts me behind on other projects.

Buy a bottle of this stuff or something like it: http://www.northernbrewer.com/shop/gas-leak-detector.html it's a lot more viscous than soapy water, so it coats things better. I found a leak with it that I never found with soapy water.

Otherwise put the soap water mix in a cup mix it up with a paint brush and put the suds on every potential leak, it will show up

Start with the tank, regulator and lines first without connecting to the keg. Turn on the main valve letting the system come up to full pressure - I usually open the regulator to 30 psi. Then shut the main valve off. Mark down the main tank pressure and the regulator pressure. Let it sit there for several days. If your tank system has a leak the first indicator is that the system pressure will slowly decrease day to day. Last to go will be the regulator pressure gauge. Holds pressure for a week, no worries. However, loses main pressure then leak in the basic set up. Real soapy water solution painted on all the threads will usually show the leak. Occasionally the regulator itself will leak, this is hard to prove and done by exclusion. Most of my leaks have been in the main tank/hardware side. If no leak here then test the keg itself when empty. I use my air compressor and put 30 psi in the keg and let it sit for a week with a pressure gauge on the outlet.