The first thing to do is to inspect fittings to be used to ensure they’re free of contaminants and/or damage. This is very important to ensure not only a leak-free seal but to prevent from contaminating newly installed or cleaned components.
Even the most minor dirt or contamination on o-ring seats can prevent a fitting from sealing once tightened. Imperfections in the o-ring seat such as this can prevent a fitting from sealing or cause an o-ring to split once tightened.
Next, lubricate the o-ring by rubbing a drop or two of oil on the surface until there is a light oil film over the entire o-ring. Install the o-ring to the o-ring bump and connect the fittings.
This is where many people unknowingly get into trouble. Contrary to popular believe, o-ring fittings don’t require significant tightening. Over-tightening can cause many problems, but the most common issues that arise from over-tightening an o-ring connection is splitting an o-ring. This can happen right away, or sometimes later on down the road.
The general rule for properly tightening an o-ring fitting is hand-tight, plus a quarter turn.
Connect the fittings and tighten by hand. Once completed, use two wrenches, positioning them ¼ turn apart [show starting position of 12 o'clock]. With both wrenches held at the 12 o’clock position, hold one in place and tightening to the 3 o’clock position with the other wrench.
Keep in mind that because “hand-tightening” can vary from person to person, it’s essential to do a thorough leak-check once the initial system charge is added to the system, and once again after fully charged. A minor adjustment to fitting tightness may be necessary.