Review on Reliance Controls THP205 Sump Pump Alarm: Flood Alert, 9V Battery, 6 Ft Wire Sensor, 105 Db, White by Sean Chambers

So I bought this item for my cesspool. The sensor has a suction cup and the top of my pump's float switch is smooth which seems like the perfect place to mount the sensor - if the water keeps rising when the float is up it means the pump is overloaded (or broken) and I want to know right away! Big mistake. So I tested the alarm by submerging the sensor in a cup of water - worked great as promised - and attached the sensor to the top of the float switch, which was the only smooth surface that worked. However, after the recent record rainfall, when the water rose well above the level of the sensor (it was at least 1/2 foot under water for several hours), the alarm remained silent. Confused, I started experimenting with it more to find out why. And of course, if you lower the sensor into a cup of water while slowly holding it horizontally, there will be a large air bubble between the wires, preventing it from working! That looks like a major design flaw. I now placed it vertically in the hole and aligned it so that one of the holes in the sensor housing was at the top to allow air to escape. Placing it this way wasn't as convenient as it used to be (no smooth, flat, vertical surface to attach the suction cup to), but hopefully it'll work better next time if it is. Your sensor is not mounted horizontally.