A recent thread got me thinking about a few jobs. We install mainly lochinvar 90% boilers. We install them according to the piping diagram in the install manual.
Anyhoo, every once in awhile we'll get one that causes a headache with air. I have purged systems and run them and thought "man that's quiet" Then a few months later it sounds like a sewer pipe. I've poured over the factory piping diagrams to see if there was a difference from mine to theirs.
I've wondered if conditions could bring air into a system from the auto vent. TBH I much prefer a bell and gosset IAS and a open expansion tank but bladder tanks are here to stay. I've wondered if a additive like a oxygen scavenger was in order, if it even exists.
I've thought about installing a hih efficiancy air scoop on the dedicated hot water maker line. But I never know which one will be a pain.