| Among other things, the caps keep the oil / sputum build-up from capriciously dripping on you and your clothes. They keep dirt out; they remove (unscrew) to allow access to the casing tube for maintenance, repairs, cleaning, etc. They do have that "weep hole" that does leak somewhat, but their presence helps contain the oil / sputum mixture to assist in moving "down-stream" towards evacuation via a water key. I believe the "weep hole" provides venting, as well -- I'm not sure, but this may help prevent a partial vacuum from forming inside the valve casing tube.
Just a few thoughts ....
Regards,
Robert Rowe |