Based in the Uk i have used Triton floats for, nearly 20 years, not had one problem with them, used on applications within the water industry ( water & sewage ) also used them on non water industry process's.I have changed them after years of use or abuse, by clients and liquids.
They used to make a Mercury float, but change to a "ball" a few years ago due to EU requirement of non mercury components in the water industry.
There range is still top class and definatly value for money.
We still buy about 30/50 a year from them ( no i do not work for them ) when compared with say Flygt Pumps ENH 10 series, it'd say it's better, only a personal view.
They also make a IS verion but you would still need a barrier relay for a use in a hazardous area.
They are based in West Auckland, Co Durham - UK
If using as a on/off you should use two floats and not just a single for both actions.
I also use the Ultrasonic / Radar / Probes (capacitance or conductivity versions ) all have there markets, and depending on the manufacturer and application they are very good and we use and service them on a dailly basis. manufacturers of these mentioned by others above all have a
good reputation.
Regards