Comparitive test for water softeners (Descaling agents) for washing mashines?

I was wondering if the Descaling agent for washing machines Calgon is so much more effective than other products with half the price or less (such as Carrefur or Lidl products). In a Calgon advertisment they say it's 3 times more effective. But can you believe them? Is there any consumer test site with such results?Comparitive test for water softeners (Descaling agents) for washing mashines?
Well, it costs as much as washing powder and the repairman told me always to use the recommended amount of detergent for your water hardness as it contains water softening agents. But if you want to save money, a good tip is replace 50gms of detergent with 50gms of washing soda which costs pennies in supermarkets and is a water softener. Excellent laundry results too.