Microphor toilet

[David Brady]

Folks,

There's an air valve under the sink in my
bathroom that seems to be leaking. The
valve is part of the control for the microphor
toilet. The valve has an input and an output
a pinhole and an adjustment thumb wheel.
Air seems to constantly leak from the pinhole.
When I ,the air leak for the pinhole
stops, after flushing is complete leaking
resumes. The valve seems to be some
sort of pressure regulator/bleed off valve.
Any idea what it does, how it should work,
and where I might find a replacement (if
indeed a steady bleeding of air is abnormal)?

TIA,
David Brady
'02 LXi, Smokey,
Va