A side stream type condenser which has a first hot well for condensing steam exhausted from a turbine and storing the condensed water and a second hot well for storing the purified condensed water to prepare for water feed to a main system includes a partition plate for defining the two hot wells. The partition plate is formed with a weir portion so that part of the condensed water in the second hot well may overflow to keep a fixed water level. The weir portion is constructed in the shape of a labyrinth and is formed with a passage normally filled up with the condensed water, and a space in the upper part of the second hot well communicates with the upper space of the first hot well through this passage only. The condensed water in the first hot well is fed to a purifying system disposed outside, and is purified therein. It is thereafter fed to the second hot well when the main system requires the feed water and to the first hot well when not, through pipe means constructed so as to feed the water selectively to the first hot well and the second hot well. The water level of the first hot well is controlled by causing the condensed water to overflow from the weir portion. On the other hand, the water level of the second hot well is controlled in such a way that the actual water level is detected by a water level gauge disposed in the second hot well, that the quantities of water in an inlet and outlet of a tank for storing the feed water of the main system are controlled in accordance with the detected water level, and that the feed water of the tank is caused to flow into the first hot well.