No dump valve.The others are right, there is an O-ring missing, more specifically, O-ring #26 from the picture. There was however some sort of sleeve as well. I'll be right honest here, I can't recall if it was a gasket or sleeve.
View attachment 909033
I would suggest buying either in 70 Shore A and the original ones are EPDM. You won't do anything wrong with NBR though.
- This O-ring (01.050.254) is a standard O-ring. BS1806-213 (3.53mm x 23.39mm).
- The O-ring (01.050.228) on newer ScubaPro BCDs is also a standard O-ring. BS1806-120 (2.62mm x 25.07mm).
Could you share the manual from where you took that screen shot ?
Thanks.