The easiest way to identify the quality of a hydrogen water cup is: buy a TDS (total dissolved solids) test pen (very cheap, about tens of yuan, can be purchased on Ebay), and fill the hydrogen water cup with water (purified water or mineral water), measure and record the TDS concentration of the raw water, do not cover the cup, and then continuously press the switch for hydrogen production 20 times, and then check the TDS concentration. If it is a good hydrogen water cup, this value should not increase, if increase too much, it means that there are a lot of solids in the water,these may be heavy metals precipitated during the electrolysis of the cup, which are harmful to the human body and are not recommended for long-term use.