The Science experiment at the link you posted actually says nothing whatsoever about proving that magnetism lowers the surface tension of water. Did you think we'd all be too stupid or lazy to actually follow the link and find out if it says what you claimed?
Magnetic laundry devices are most certainly a complete scam, and I personally performed a first-hand experiment to prove it. People who sincerely think they work are deluding themselves, and there are lots of reasons they do so that aren't really worth going into here.