It is very easy to magnetise water once it has come from the tap. You simply place magnets of a sufficient type and strength in the water, these tend to be Neodymium magnets and they have to be coated in a non corrosive type substance to actually stop them from rusting. The easiest way is to use what is called a water wand or a coaster which is placed into the water or you place the water on a coaster. The difference between using a wand to a coaster is, when you place the wand into the water the magnetism is taken quicker because the wand is placed directly into the water. If you place your glass or cup or your bowl or jug of water on to a magnetic coaster it takes a lot longer for the magnetism to go through because it has to penetrate through the vessel's layer whether it be glass or plastic to actually get the magnetism into the water so you would need a stronger magnet to actually do the job ,so it is better to use a wand that actually is immersed into the water.
Generally in a glass of water you would immerse the wand for 15 minutes or in a large volume of up to 2 litres would take one hour. So once you have placed the wand in the water for 15 minutes or one hour the water will then take up the magnetic charge and it would then be magnetised.
You do not have to worry about leaving magnets in the water too long because the water is like a sponge it will only take up as much magnetism as is needed and then it will stop absorbing it so if you left your magnet in the water overnight it will not have any detrimental eff
However, if you live in a hard water area, your water will contain large amounts of limescale, this will eventually attack the Rhodhium coating on the wand and brown spots will appear. This will not impede the function of the magnets but it will cosmetically look unappealing. To prevent this from happening, always immerse the wand for the minimum period required (i.e. 15 minutes or 1 hour) and then remove the wand, this will prevent limescale damage.
Debbie Shimadry is qualified magnetic therapist and pain nurse specialist. She appears on several BBC radio stations as an expert guest on magnetic therapy and is also the managing director of leading magnetic therapy company worldofmagnets.co.uk. To find out more on how magnetic therapy can help you, visit magnetictherapyfacts.org.