If you look at their guarantee, you can have your money back if you can see that it hasn't made any improvement after three months. You'd be lucky to see there's a problem on a new system in 3 months. The guarantee is not brimming over with confidence is it?
Search the forum for water conditioners or possibly Cranfield University. They wrote a report on these, and similar devices, I'll leave you to form your own conclusions from the report.
I don't know manufacturers who recommend this type of device, at least in for oil boilers.
A reliable device is Combimate, which a silicone-polyphosphate device. The process is well known and so is how it works. Made by Cistermiser, again, try searching the forum.
I have been fed garbage about these electronic devices, such as you can wind the coil round steel/iron pipes and it will still work, (don't ferrous metals "short circuit" magnetic flux?) and yet it won't work with lead pipes which short out magnets. Well, try putting a lead cover over a magnet and picking up some nails. It works fine; so that bit of info was duff then.
As I understand how these devices work, it is they get consumers to part with their money and give a nice guarantee which is not too long.
If you are buying one of these devices, you may find it will be benefical to spend a little more and buy a magnetic bracelet as well. This will cure all manner of ailments, and you could hang it over the bath tap to treat the water and save soap as well.
