Oxidation Reduction Portential : ORP or Redox factor

This ORP factor is one of the most important characteristics of Kangen Water because this is what distinguishes it from any other water on the market. Including its lesser grade cousin, Ionized Alkaline Water. In short, it measure the anti-oxidizing strength of the water.

When you reduce active oxygen from the water you increase its power to slow down the oxidation process by eliminating Free Radicals safely from your body. This effectively helps to slow down the aging process. Active oxygen is not healthy for the body and is what you feel if you have ever exercised too hard and felt your lungs burn. This is the type of oxygen reduced and removed from the water. Dissolved Oxygen is the kind that what you want left in the water to create a healthy and strong body.

Kangen Water
OH- > H+ = Alkaline
Gained Negative Electrons (e-)
Negative ORP Reading
High pH value          Acidic Water
OH- < H+ = Acidic 
Lost Negative Electrons (e-)   
Positive ORP Reading
Low pH value        
Ideal Effective ORP Range:

–250mV   ~   –400mV

Active Oxygen + Active Hydrogen (H+ + e-) = H20 (WATER)

The reading of mV indicates the millivolts of hydrogen electrons present in the water available to bond with the free radicals and flush them out. These machines can produce incredibly functional water, called Strong Kangen Water (ORP: below -750mV) and Strong Acidic Water (ORP: above + 1150mV). While they are not meant for drinking, the power of these two waters, particularly, Strong Acidic Water has been recognized and widely used in various medical practices in Japan for many years.

Enagic made the best device with the best lifespan

ELECTRODE SIZE AFFECTS LIFESPAN!

The ability to maintain a stable ORP range rest on the total surface area of the electrode plates. Not only will small plate size negatively affects the ability to produce water with an useful ORP (i.e. ORP between -250mV ~ -400mV), smaller plate size actually speeds up the electric polarization exponentially, reducing the electrode plates' lifespan dramatically. Once the electrode plate reaches its life cycle, it can no longer produce water useful ORP, literally rendering it useless.

Small Plate Size Reduces Lifespan Exponentially

The Useful ORP Range Must Be Smaller Than -250mV

Plate Size Less Than 600cm² = Only 1 Year Lifespan

This is why the SD 501 is gonna work perfectly for about 15 years...and more

It comes with 5 years full guarantee and it is approved as a medical device in Japan