What’s the meaning of TDS in drinking water and is it a good
measure of quality? We take a look at what constitutes TDS in water and examine
all the facts around the different levels of TDS in water. What’s a good TDS
level and what’s a bad TDS level?
TDS stands for total dissolved solids and is a measure of
all the dissolved organic and inorganic substances in drinking water. On the
face of it, it seems like a good measure of the quality of our drinking water
as we’d expect to not want lots of dissolved contaminants in our water. But the
truth isn’t so straightforward as some dissolved substances in drinking water
occur very naturally and are good for our health. Therefore, TDS as a measure
of the quality of our drinking water may be misleading.
TDS levels can be misleading
‘TDS is relatively easy to measure with an inexpensive meter. Because of its availability and ease of use, the TDS meter can be used as a misleading marketing tool by the reverse osmosis technology industry to convince consumers that their water may be causing harm,’ concludes Dr Danielson. ‘However, let’s be clear, the mere presence of TDS does not indicate unhealthy drinking water.’
Richard E. Danielson, PhD is author of over sixty publications, reports and presentations on water quality and environmental and public health microbiology
What are good and bad
TDS levels?
In 2003, The World Health Organisation (WHO) convened a
panel of taste testers and decided on the following scale:
50 - 300 TDS = excellent
300 - 600 = good
600 - 900 = fair
900 - 1,200 = poor
1,200+ = unacceptable
This is all based on taste, smell and feel rather than
health and safety, so it’s subjective. The other problem with measuring TDS in
water is that it’s a blanket measurement. So we should take into account what’s
actually being measured.
What are TDS made up
of?
TDS are pretty much anything in water that isn’t the actual
water itself - your basic H20. Water will try to absorb and dissolve anything
it comes close to - that’s why it’s called a universal solvent. If it sits in a
plastic bottle for long enough, that plastic, being slightly permeable, will
begin to leach into the water. If you sit an open glass of water next to
something with a strong smell, given the chance, the water will begin to smell
the same.
Our drinking water will naturally pick up a fair few passengers
along its way to our taps. For a start, historically our drinking water has
always come from surface water (from rivers, lakes and reservoirs) or
groundwater (from the cracks and spaces between porous underground rocks, soil
and sand). Water from both of those sources will have picked up stuff like
minerals, dirt, microplastics, pesticides and herbicides. Our local water
treatment works will then add chlorine to kill the bacteria that grows in
water. Even after that, our water may still pick up dirt and rust from the
pipes leading to our properties. If any of these are present in your tap water,
an easily available TDS meter will measure the amount there is.
Why is the TDS level
not a good measure of the quality of water?
A TDS meter will indiscriminately measure the amount of other substances found
in our tap water, no matter what they are. While no-one wants bacteria, dirt,
rust, sand, metal, microplastics, pesticides, herbicides and chlorine in our
drink, a whole load of naturally occurring minerals are a good thing. Bottle of
mineral water, anyone? Yup, huge business has been found from bottling
groundwater at source rich in minerals and selling it to health conscious
consumers. Some companies even add minerals to the water to increase its health
value. So having minerals such as calcium, magnesium and potassium in your
drinking water is a good thing - and a TDS meter will pick these up.
We asked Richard E. Danielson PhD, Environmental and Public
Health Microbiologist, for an independent view on TDS levels in water. Here’s
what he said:
‘Humans require inorganic salts and minerals to maintain
natural health. There are those in the water treatment industry who would label
TDS in general as a detriment to water quality and human health. However, TDS,
and especially magnesium and calcium, can contribute up to about 20% to the
daily requirement of these available minerals.’
These are the TDS levels in bottled mineral water, and how
the WHO would class their taste:
Perrier = 47 (The WHO would class this as tasting ‘flat’)
Fiji = 222 (WHO class = excellent)
Hildon = 312 (WHO class = good)
Evian = 357 (WHO class = good)
San Pellegrino = 1109 (WHO class = poor)
How to reduce TDS in
water
‘There are other constituents (in TDS, besides natural
minerals) of immediate concern… such as chlorine, pesticides, heavy metals,
microorganisms, and pharmaceuticals,’ says Dr Danielson.
A water filter will reduce the TDS level in drinking water.
An active carbon filter will remove chemicals, including the chlorine added by
the water treatment works, along with substances including copper and lead.
Along with an activated carbon filter, the Virgin Pure system has additional
filters which will also reduce dirt, microplastics, rust, sand and sediment. It
also contains an ultraviolet light which kills off bacteria and stops it
growing once the disinfecting chlorine has been removed.
While a reverse osmosis system will remove everything from
your tap water, including the healthy minerals, the Virgin Pure filtration
system leaves in all the naturally occurring minerals such as calcium,
magnesium and potassium. All of which are good for our health. We even have a
pre-filter which prevents the calcium and magnesium from bonding and creating
scale.
Therefore, the TDS level in Virgin Pure water will include
those healthy minerals, the same as it would in shop-bought mineral water.
Sources:
United States Department of Agriculture - Vitamins and Minerals: https://www.nal.usda.gov/legacy/fnic/vitamins-and...
Water Quality Association - Consumption of Low TDS
Water, 2013
World Health Organization - Total Dissolved Solids in Drinking Water,
WHO/SDE/WSH/03.04.16. 2003
World Health Organization, EU Water Framework,
EPA
