Planted Tank Enthusiast
Join Date: Apr 2004
Location: Des Moines, Iowa
I run a 2.5 pound tank on a 75, lasts a good 3 months with a very high bubble rate so I'd guess you have a problem. The silicone will tend to harden from CO2 exposure which first has the affect of deteriorating the physical connection at the regulator and reactor and leaking. You could cut off an inch at either end and that will be a temporary fix. You should get a good CO2 rated tubing. That would fix that deficiency if that's the problem.
If you look at the mating surfaces on the regulator and the tank, you'll see that in reality, the threads have nothing to do with the seal other than to provide the force to hold the mating surfaces together. The only thing that seals the connection is the washer that came with your regulator. If the gas were to leak past the mating surfaces, the threads would be sealed with tape but the gas would leak past the collar that holds the nut on so taping the threads won't stop leaks.
If the connection is leaking, it either isn't tightened down enough or there is something preventing the washer from being perfectly compressed between the mating surfaces. Could be a scratch or gouge in either of the surfaces, dirt, anything. Tighten the connection more or better, replace the washer, check the surfaces and then crank it back down.
The reason some people seem to have success stopping the leak by taping the threads
is due to the fact that when they put the tape on, they are essentially lubricating the threads so they tighten it more than it was without tape without realizing it. The problem is, the tape can flake and wreak havoc on a regulator. I realize that to the average person, it seems like they are tightening the regulator enough, even too much, but you have to remember, you're also tightening it to stop something that's running almost 1000PSI. If you're really paranoid about busting the stem or something, try a bit of silcone applied to the threads to lubricate them.