Would you be able to check if water is hard by using a detergent

Would you be able to check if water

is hard by using a detergent? 

Answer: Detergent works both in hard water and soft water, it cannot be used to detect if water is hard or not. 

Detergents are ammonium or sulphonate salts of long chain carboxylic acids. The charged ends of these compounds are effective in hard