I need a cap for an old sewer cleanout. The house was built in 1954, and I figure the sewer cleanout is probably from then.
I'm trying to figure out what exactly I should order. I tried to measure it. The inner circle diameter (Marked with a red line in this photo) looked about 3.25" The outer rim of the inner circle (yellow line) was about 4.5". The diameter of the whole thing (blue line) is about 6.5". I'm thinking maybe I mis-measured the inner ring and maybe this 3.5" brass plug on Amazon is what I need? https://www.amazon.com/Oatey-42373-...==&sprefix=sewer+cleanout+plug,aps,267&sr=8-5
Does anybody have extensive experience with old sewer cleanout standard sizes? Any constructive comments welcome. Thank you.