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Hello allBelieve it or not, there's a good chance of buying one of those screwed bronze lift check valves new from Johns valves (which I think is the brand of the valve Ian has posted)It's called a bronze T4M check valve from Johns Valves on (03) 5336 2113In this link is a schematic of them.https://irp-cdn.multiscreensite.com/c7793c35/files/uploaded/T4M%20Braemar%20Bronze%20Check%20Valve.pdfFailing that, there's probably one in the shed somewhere.Cheers ScottPS: nothing missing on your valve Emu. It has to be placed in the horizontal axis though.
Scott , the link provided showing the PDF of the Lift Valve doesn't seem to be bi-directional .according to my interpretation of the schematic diagram .