Ro/di tds questions

well its funny ive been in the hobby for 2 years and i never owned a ro/di unit i ALWAYS just bought water from the store...and i never really understood what tds rating is...and what it exactly means interms of the water quality...ok stupid example i dont know the difference between filtered water with like a "pur" unit or brita or ro/di water...

 

TDS is Total Dissolved Solids. For our tanks the less the better. The water from the Brita filters is run through carbon which removes most chemical impurities. Ro/di is Reverse Osmosis/De-Ionized water. The reverse osmosis is done through a specially design film that traps most contaminants that the sediment and carbon filters can not remove. The de-ionization unit removes the the elements leaving pure to almost pure water.

 

Total Dissolved Solids is a measurement of the electrical conductivity of all things present in water. Its not an exact measurement of one thing in particular only that there is something present that conducts electricity. True deionized water is non conductive, in theory you can stick your hand in it along with a live electrial cord and you would feel nothing, not that I would recommend it!

A RO membrane is a semipermeable plastic film with millions of tiny microscopic holes that is wound around a core. When you run pressurized water on one side of the membrane pure water molecules pass through but contaminants get left behind and flushed away with the 4:1 waste ratio necessary to operate. RO is almost always preceded by a particulate or sediment filter and carbon to remove chlorine which can damage a RO membrane. RO/DI units have a fnal deionization which removes anything which the membarne misses that is still electrically conductive, often phosphates, silicates and forms of ammonia wil still be present in tracye amounts as the membrane is only 90 to 98% efective at them.

Pur and Brita filters are activated carbon and often some form of sediment filter to remove large particles but in no way similar to RO or RO/DI, they are basically taste and odor filters.