Quote Originally Posted by Gary L View Post
If you have a pressure cap (by that I mean one that is designed to open at a pre-set pressure)...
They're not designed that way, Gary.

The VWoA group uses an expansion cap with a one-way valve, designed to allow air *in* when in vacuum, but block exit of any liquids, gas, or pressure *out*. I only mentioned the "last resort" for the cap because that's what typically fails first (if you don't pop a hose). I've link a photo at the bottom.

But this is not necessarily germane to the conversation. I think Bob's point is that we now have a requirement for a "catch can", a catch-all (har-de-har) rule that doesn't necessarily apply to all systems. I was simply pointing out that the rule was not intended to apply to systems such as the VWoA's; you certainly don't want to hack into these systems to add a catch can, it would be problematic, dangerous, and flat stupid.

If anything, the rule will be enforced intelligently, i.e., tech inspectors will recognize this rule doesn't apply to these systems; if not then it will need to be adjusted accordingly. - GA