If your regulator is leaking where it joins up with your main Power Tank valve, you may need to replace the seal. This seal looks like a flat rubber washer and we call it the Never Lose Seal because it is designed to stick in your regulator nut and not fall out.
If your seal is cracked or hard, it's time to replace it. The most common cause of failure is over tightening of your regulator nut. It only needs about 15 ft./lb. of torque or to be "two-finger tight."