Love posts like this and registered just for this. I am considering building a couple of barrel pumps after seeing this post and seeing the price tags for 6" pumps.
I have a few questions.
1) I am unclear on where the gasket (shown in pic 7 and 8" goes and what it does in the pump as whole.
2) What kind of dishwasher check valve you suggest for this. I see various designs out there and Im not sure which valve to obtain for this project.
3) Why rivet the top two pieces together and not just use pvc primer/glue? Simply to avoid buying the glue if you did not have some on hand or is there something Im not getting here?
4) The top cap remains unglued from the main body, correct? I do not see how that stainless pan screw holds it together under vigorous pumps and does not mutilate the discs on the up stroke. Could you expand on that a bit?