I tested the filtered water, using a TDS meter, and it is higher than Zero. Why is this?

Seychelle filters remove heavy metals such as arsenic, lead, cadmium, nitrates, chromium 6, etc. but do not remove "trace minerals" which are known to be beneficial.  They are known as the "good-for-you-minerals" such as sodium, iron, zinc, calcium, magnesium, potassium, phosphorus, etc. Trace minerals are generally needed in quantities of only a few milligrams (mg) or micrograms (mcg) per day. "Keeping a balance level of minerals in every organ, tissue and cell of the human body may be a prominent key to maintaining a healthy existence. Minerals are crucial for many body functions including transporting oxygen, normalizing the nervous system and simulating growth, maintenance and repair of tissues and bones", according to NFM's Nutrition Science News, December 1995.

These inorganic minerals will read higher on a TDS (total dissolved solids) meter. The basic media, in the Seychelle filter, is a proprietary powder activated coconut carbon that is organic. The powder activated coconut will show a higher conduction and increase the parts per million of total dissolved solids. Trace minerals make up a good portion of Total Dissolved Solids therefore it will cause TDS readings to vary.

Filtration systems like RO (Reverse Osmosis), Distillation and Deionization - including systems like Zero Water - remove all total dissolved solids, including trace minerals that are beneficial to your health. Therefore, a reading with a TDS meter will be lower because it decreases the parts per million (PPM) of total dissolved solids.