Engine

Water at the tail pipe can be a byproduct of a properly functioning catalytic converter, but the multiple symptoms suggest a leaking cylinder head gasket. You can verify that by adding a small bottle of dark purple dye to the coolant. It will show up later under a black light as a bright yellow stain. If it shows up inside the tail pipe, the head gasket is leaking. The level in the coolant reservoir will be going down too.