Level Sensors for Building Water Tanks

A hydrostatic or ultrasonic transmitter gives a continuous reading, so you can see the exact level and trend it over time. A pressure switch is enough if you only need to start and stop the transfer pump at one set depth, without a continuous value on the BMS.

A capacitance transmitter measures water, diesel and edible oil, because the probe responds to the liquid's dielectric property rather than its conductivity. Hydrostatic and ultrasonic transmitters are usually specified for water. Tell us the liquid and tank depth and we'll confirm the right probe.

Most Trumen and Beck level sensors give a 4 to 20 mA signal that any BMS input card reads directly. The hydrostatic transmitter and the ultrasonic transmitter also offer RS485 Modbus, which lets one controller poll several tanks over a single cable instead of wiring each one back separately.

A level switch, like the pressure switch on this page, gives one on/off contact at a fixed depth, enough for pump start/stop or a single alarm. A level transmitter gives a continuous signal proportional to the level, so the BMS can display the exact reading, trend usage and set several alarm points on one device.

A submersible hydrostatic transmitter is the usual choice, because it hangs in the sump and reads the water pressure above it down to a small footprint. An ultrasonic transmitter also works if you can mount it above the sump opening, clear of any turbulence from the inlet pipe.

Yes. Hydrostatic and ultrasonic transmitters, and the low-range Beck transmitter, all report fire water tank levels to the BMS alongside cooling tower and domestic tanks. They don't replace any dedicated level devices required by fire regulations, so check what your fire system separately needs.