Abstract: A steam trap comprising a housing forming a low pressure chamber and an it opening and an outlet opening and a valve seat formed at the inlet opening. A thermal control device filled with an expansion medium is disposed in the low pressure chamber, and includes a locking part for the valve seat actuated by the thermic control device. A separating wall divides the low pressure chamber into two chambers, one of which is connected to the inlet opening and containing the control means, the other of which is connected with the outlet opening. The separating wall has a porthole positioned on another side of the control device with respect to the outlet opening in radial and/or axial direction relative thereto.