What Does A TDS Meter Do?

Recently I was asked by an Aquasana customer why their TDS meter was showing no change to the TDS reading between their tap water and water filtered by their Aquasana filter. After penning a response to this particular customer it struck me that perhaps this is a question other customers and potential customers may have as well.  If so, please read on.

TDS is Total Dissolved Solids.  Water dissolves the minerals present in the rocks and soil it passes over or through after it falls to the ground as rain.  As it dissolves these minerals, they remain in the water at varying levels of concentration.  This is a very natural process and it helps make water taste “right” by slightly raising the pH of the water.  The most common minerals found in water are Calcium, Magnesium, and Sodium.  Some areas of the country have higher levels of these dissolved minerals in their water making it “hard” and other areas have lower levels.  From what I have read, anything under 500 mg/L (or ppm) is good and 300 mg/L is considered excellent.  As the TDS level goes below this level – as the minerals are removed – the water has a lower pH and becomes more acidic or corrosive.  You will notice this in the taste of the water.  TDS levels over 2000 mg/L are considered non-potable (don’t drink that stuff).

One of the reasons the Aquasana filtered water tastes so good is because we utilize a selective filtration process.  All of our drinking water filters use the same process and we call that the Aquasana Claryum® Filtration Technology. Our filter is certified to remove 66 contaminants including chlorine, chloramines, lead, pharmaceuticals, pesticides, herbicides, etc.  However, we specifically DO NOT remove the minerals in the water.  We filter out the bad, but leave in the good.  This Claryum selective filtration process will make your water taste more natural (I like to say better) because we filter water back to the form nature intended.

The Aquasana Claryum Filtration Technology utilizes three main processes.  First, carbon absorption – this removes most of the organic compounds (chlorine, pharma, pesticides, herbicides, etc).  Your body is mostly carbon, so this filtration process acts much like your body would.  Our filtration process here is better than gravity pitchers because we use a dense carbon block and pressure instead of granulated carbon and gravity.  The result is much greater contact time of the water with the carbon even though the filtration process is faster.  Cool, huh?  Second, mechanical filtration – this removes particles larger than 0.5 microns such as giardia or cryptosporidium (which are chlorine resistant parasites).  You won’t get this kind of filtration from most gravity filtration products either.  You can only get this with extremely slow filtration or by utilizing pressure.  Last, ion exchange – this is how heavy metals like lead and mercury are filtered.  Basically, we have a potassium ion mixed with the carbon which is designed to grab any particles with a positive charge (i.e. heavy metals) and replace those particles with potassium.  This filtration process can actually result in a small increase in TDS concentration.

All that said, there are some dissolved solids that you do not want in your water.  They are very rare in tap water, but things like arsenic can find its way into tap water at low levels of concentration.  Your local water supplier is required to do a water quality test and make the results public.  If there is arsenic in your water, it would show up on this report.  Additionally, fluoride is added to tap water in most cities in the US. If you have arsenic in your water or you want to remove fluoride, I recommend the Aquasana reverse osmosis filter and re-mineralizer.


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