What is this? What is this? sundy1958 (Electrical) (OP) 22 Jul 16 15:19 I have a bunch of these. I don't know what they are. Do you? If they are not worth anything they are going to scrap. RE: What is this? racookpe1978 (Nuclear) 9 Aug 16 04:02 Could be a check valve (with a flapper) .. What does the back side look like?