Leaks in the System
Pipe thread fittings in high and low pressure breathing gas systems are often used as an alternative to straight thread O-ring or welded fittings due to cost, complexity and strength issues. Pipe thread fittings offer an alternative to large bend radius welded or compression joint systems, and produce exceptionally strong systems, however, shock and vibration especially in portable systems can cause movement between joints resulting in leaks. Unlike O-Ring fittings, minor pipe thread fitting leaks will not suddenly or drastically increase because the locking nature of pipe threads. Teflon tape is used primarily as a lubricant to keep the threads from galling but also acts as a sealant. Leaks in O-Ring fittings cannot be tolerated because the seal is being made by only the O-Ring, between two surfaces. Leaks will normally increase and often parts of the O-Ring will extrude, causing sudden massive leakage.
Minor leakage in pipe thread fittings are common, and should be expected. They do not generally pose a operational hazard, or reduction in operational capability as long as the leaks can be identified and quantified. All leaks should be repaired as soon as possible.
The only proper way to remedy leaks in pipe thread fittings is to depressurize the system, disassemble the joint, remove old sealing tape, brush the threads, and then re-tape and remake the joint. Because this is often difficult or impractical to accomplish in the field, minor leakage can be an acceptable alternative to field repairs in order to safely continue with diving operations.