Or you buy a bleed valve for the system.

"J. Clarke" wrote in message
...
billh wrote:

I have heard of some saying their system can collapse the thin stuff if
all their gates are closed but I have my doubts unless their system is
extremely tight and have some damaged duct (badly flattened). If you
think
you are approaching this situation just bleed a bit of air - yeah, I
know
that isn't the idea but life isn't perfect at least on the cheap.

The problem with "just bleed a little air" is that you don't know you need
to until it's too late.