I cast a Pro Seal (PRC 890) gasket onto the bulkhead so the flapper will
seal well.
It also seems to quiet the valve noise substantialy as it now closes onto a
soft surface.  Do it just like a micro release using packing tape but wait
at least 24 hours before opening.  The set time is very slow to full cure.
Walter Dodson  IV-P going into upholstery soon