Quote Originally Posted by Solvo View Post
Why would the vent be in a part of the cylinder that the seals pass over?
The output vent to the storage is most likely in the end, I dare say the intake is likely piped to that same end, or possibly even just a valve in the piston itself. It doesn't have to be in the sidewall of the cylinder, there are other options!
Yes, but pumpers are usually simple animals, the cylinder vent/air inlet hole is a very easy and simple system that works. My Blue Streak had a vent hole and was on its original pump seal after 40 years, still pumped fine with no leaks.