The Shisha give you the way. This seal is created by a rubber base grommet, which is placed around the part of the shaft that fits into the base opening.

And every time with is this possible. One is the hose adapter, and the other one is the air purge valve (or release valve). The air purge valve allows air inside the base, and can release stale smoke when you blow through the hose. There is a small ball bearing inside the purge valve. Be careful not to lose it when cleaning the hookah.

Then comes the hose adapter, which is where you insert one end of the hose, and is once again sealed tightly with a rubber grommet that is nestled inside the port.