Am I a sucker? I just bought an Ecozone Magno Ball for about £15 - I am told it is an effective non-chemical way to remove limescale from washing machines (and dishwashers but I don't have one of those). It basically acts by crystalizing the limescale, making it impossible to stick to clothes, pipes, or heating elements. It can be used in conjunction with those Eco Balls that I also use - hey even had a juggle with the balls before washing my smalls today?!
If you still use detergent then the manufacturers of the ball claim it can reduce the amount of detergent by up to 70% - also no more anti-limescale tablets and you can reduce the machine temperature.
I am told by a washing machine repairer that our hard water leads to limescale build-up on the heating element. Over time, as this limescale builds up it can cause the heating element to fail and damage the drum, pipes and hoses.
If it does all it says then the ball should save on heating and the life of the machine...