's vent has been heavily modified. To start we have dual gate valves on the stern:
We also have the original vent plumbed into the cockpit so I can hear when the air stops gushing out of the tank. There is a dipstick tube on the original vent location just in case you don't trust the lack of air when it stops purging onto your leg LOL!
Just in case your in a really big hurry or want to get the very last bit of air from the tank you can go forward into the V-berth and open a front valve to assist in filling the ballast tank:
This vents to a covered thruhull in the front bow, which the site says I can't post a picture of due to the 3 image max...
OK, maybe it was a little overkill but it does make for a nice fast fill and dump of the ballast tank.