The picture at http://dotcomdetox.com/piano is the same suction box
I pulled out of my piano.  I know for sure that mine had no valve.
I also had the same symptoms as she described, where I could reroll
but not play.

When I pulled out the pump and taped off all the openings, it worked
just fine, holding air for at least 20 seconds.  I put it back in,
and had the same problem.  Eventually I heard the air coming from
the vacuum box while I pumped, and realized there was no check valve.

I hope that the original poster can seal off that hole in the
reservoir and get back a working player as easy as I did.

Michael Hamilton