What is a Flow Switch and how do they work?

What is the best flow switch for low flow rate

Video for tamper switch or supervisory switch pls?

thank you

What if I installed flow switch vertically..?
Is there any misbehave in switch operation occurred?

Badly explained

I have a pic for some of elements for chillar can I contact with u

My problem is water continuously flowing when a water closet valve malfunctions or somebody forgot to turn off the water flowing in the washing machine or someone forgot to turn off a water tap. Continuously flowing water results in higher water bills. I need to be notified or some kind of alarm turns on when continuously flowing water occurs.