Most of the UK has very hard water which is water that has Calcium Carbonate (lime) disolved in it. This comes from when the water is passing through the ground to the point where it is collected. When water is boiled it gives off the lime and on most surfaces this will stick to it and become limescale. This limescale builds up very quickly in Steam Cleaner Boilers and is, quite simply, "Death" to steam cleaners with conventional boilers. 70% of Steam Cleaner breakdowns are caused by limescale.
This, simply, does not happen with Steam Clean Systems machines as they have patented self descaling boilers.
Click on the video to the right to see how these work.