Use this vertical float switch from Sensata Cynergy3 for accurate liquid level detection in small tanks. This magnetically controlled device has a reed switch to automatically turn the pump on or off to prevent spills or excess emptying. It has a cable that's sheathed in PVC for durability and resistance to wear. The cable is 1m long to give you easy access to a power source. This type of float switch is commonly found in water treatment plants and beverage production facilities.

• Broad operating temperature range of -20°C to +100°C for use in demanding conditions
• Nitrile rubber gasket is resistant to chemicals and wear to prevent leakages
• Low switching current of 600mA for energy efficiency
• Compact dimensions of 75 (length) x 21.5mm (width) for installation in tight enclosures
• Switching function can be reversed by inverting the float for versatility

You can mount this float externally using compression seals, so you don't need access to the inside of the tank.