Ben goes underground, drains a puddle to summon smoke monster

Ben pulls the bookshelf out and goes to his secret room. He pushes a button next to the light switch and we can hear something metal move. He goes to the wall behind the clothes that are hanging and pulls it back revealing the hieroglyphics door. On the other side of the door, there is a set of stairs. Ben lights a lantern and goes down. At the bottom of the stairs there is a small tunnel which Ben climbs through. As Ben comes out of the tunnel to a larger room, there is a dirty puddle. Ben sticks his hand in the water, turning something to release the water. The water drains down the small hole. Ben looks down towards the hole and says "I'll be outside." He takes the lantern and leaves.

So what is the deal with drain? I'm sure there's more to what Ben did to call the monster than it seems here. Does that water draining send a signal to the monster? That was just bizarre.