Water Leakage
A leak of water is a water leakage.
ろうすい
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
どんなに値段が高くても、その漏水検出器を買うべきだと思います。
No matter how expensive it is, we should buy the water leakage sensor.