Devices and methods for a vertical float system. A float guide, located in a tank containing a fluid, has first and second sections with a first diameter and a third section between the first and second section. The third section has a smaller, second diameter. A float is slidably attached to the float guide in the third section. The system includes a switch and a level sensor located in the first section or the second section. The switch becomes activated when the float contacts the level sensor. One of an inner face of the float and the third section of the float guide has projections arranged in a contiguous pattern around the one of the inner face of the float and the third section of said float guide. The projections are shaped to establish point contacts between the float and the float guide in the third section.

A floatable flood detector has a watertight housing that carries internally a wireless transmitter and a fluid sensor. In the presence of sensed fluid, an alarm message can be transmitted by the transmitter to a displaced monitoring unit. The sensor has a portion exposed to the fluid of interest outside of the housing. The antenna is carried, at least at a fluid level, relative to the floating housing.

An aerially controlled sludge level detection system is for determining a sludge level in a wastewater reservoir. The system may have a drone and a sludge level detection tool suspended from the drone. The drone may be operable to lower the sludge level detection tool into the wastewater reservoir and raise the sludge level detection tool out of the wastewater reservoir. The sludge level detection tool may have a longitudinally extending gauge. At least a portion of the gauge at a distal end may be hollow to allow a volume of a fluid and a volume of the sludge from within the wastewater reservoir to enter the gauge when lowered into the wastewater reservoir. The sludge level detection tool may also have an analyzer connected to the gauge for analyzing the volume of the fluid and the volume of the sludge within the gauge.