PROBLEM TO BE SOLVED: To make it possible to control a high water level state and a low water level state not by depending on electric control, and to adjust a water level of nutrient liquid to an optimum level for growth of plants.SOLUTION: A water level regulator 6 comprises: an overflow pipe 61 having a first outflow port 61a and a second outflow port 61b provided at a position lower than the first outflow port 61a a valve member 62 provided so as to form a closed state where the second outflow port 61b is closed and an open state where the outflow port is opened and a water expansion member 63 that forms the closed state of the valve member 62 in an unexpanded state and moves the valve member 62 into the open state in an expanded state due to water absorption.COPYRIGHT: (C)2015,JPO&INPIT【課題】高水位状態と低水位状態を電気的な制御によらずに行えるようにし、また、植物の成長に合せて養液の水位を最適にする。【解決手段】水位調整器6は、第1流出口61aおよび当該第1流出口61aよりも低い位置に設けられた第2流出口61bを有するオーバーフロー管61と、上記第2流出口61bを閉じる閉状態と開く開状態を形成するように設けられた弁部材62と、未膨張状態では上記弁部材62の閉状態を形成し、水吸収による膨張状態では上記弁部材62を移動させて開状態にする水膨張部材63と、を備える。【選択図】図3
