Drain water heat recovery tank - has low-level outlet acting as siphon when flow is heavy

The tank recovers heat from drain water, having an inlet for the latter and a heat exchanger with inlet and outlet for washing water. An overflow is provided, the level of whose outlet (9) is below that of the tank bottom (6), so that it acts as a siphon emptying the tank in the event of a large incoming quantity of drain water. The overflow can comprise a pipe (8) leading from near the tank bottom to an overflow height (h) out of the tank and then downwards to the outlet, where there is a throttle (10) generating the necessary vacuum where there is a large quantity of drain water flow.