J. Phil Thien's Projects

Maybe this will work for you.  I have ordered one and will report results in a few weeks, but here is the link for your review:

http://shop.centralvacuumfactory.com/vacvalve-relief-valve-central-vacuum-systems-p-954.html

Nice work, really !

Residential central vacuuming often (but not always) uses a pressure relief valve that is tune-able / adjustable AND inexpensive.  It appears to be a ready-made version of the home made valve discussed on this thread.  I have ordered one and will report the results, but will offer the link in the mean time:

http://shop.centralvacuumfactory.com/vacvalve-relief-valve-central-vacuum-systems-p-954.html

Regards,

David Grimes