What should be in my water?

What is TDS?

Total dissolved solids (TDS) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in molecular, ionised, or micro-granular (colloidal sol) suspended form. The principal application of TDS is in the study of water quality for streams, rivers, and lakes. Although TDS is not generally considered a primary pollutant (e.g. it is not deemed to be associated with health effects), it is used as an indication of aesthetic characteristics of drinking water and as an aggregate indicator of the presence of a broad array of chemical contaminants.

TDS is expressed in units of mg per unit volume of water (mg/L) or also referred to as parts per million (ppm). For example, tap water in Barcelona varies between 200-600 mg/l, Madrid 50 mg/l, Palma de Mallorca 400-900 mg/l.

The TDS measurement of water is actually the measurement of its conductivity, so indirectly a value for the amount of ions dissolved in the liquid. There are two different forms of ions in water, the cations calcium, magnesium, sodium and potassium and the anions carbonate, bicarbonate, chloride, sulphate and, particularly in groundwater, nitrate. Cations are positively charged ions and anions are negatively charged ions.

Therefore a high TDS value means a high amount of dissolved Minerals.

In a study by the World Health Organisation, a panel of tasters came to the following conclusions about the preferable level of TDS in water (mg/l):

  • 50 – 300: Excellent
  • 300 – 600: Good
  • 600 – 900: Fair
  • 900 – 1,200: Poor
  • Above 1,200: Unacceptable

What is PH?

The pH value of a water source is a measure of its acidity or alkalinity. The pH scale is a set of standard solutions whose pH is established by international agreement. pH value indicates whether a fluid is strongly acidic (pH value 0), neutral (pH value 7) or strongly alkaline (pH value 14).

The pH scale is logarithmic, which means that each step on the pH scale represents a ten-fold change in acidity. For example, a water body with a pH of 6.0 is ten times more acidic than water with a pH of 7.0. And water with a pH of 5.0 is 100 times more acidic than water with a pH of 7.0.

While the ideal pH level of drinking water should be between 6-8.5, the human body maintains pH equilibrium on a constant basis and will not be affected by water consumption. For example, our stomachs have a naturally low pH level of 2 which is a beneficial acidity that helps us with food digestion.

  • Soft water contains relatively few minerals and lathers easily.
  • Hard water is rich in minerals such as calcium and magnesium, which is the cause of “scale” in kettles.
  • Water hardness is usually expressed as the number of parts per million (ppm) of calcium carbonate present in the water.
Hardness in mg/l CaCO3
Hardness level
< 60 mg/lSoft
60 – 120 mg/lMedium-hard
120 – 180 mg/lHard
> 180 mg/lVery hard

Which minerals are in potable water, and what do they do?

If we talk about minerals we need to know that minerals exist in two different forms, organic and inorganic. In water as it is the case in milk, we find only inorganic minerals that means the mineral is in an inorganic binding, looking at the example of calcium this translate into the following.  Calcium sources like calcium carbonate, calcium phosphate and calcium oxide are inorganic and can be found in water or milk. On the other side organic calcium sources like calcium formate, calcium gluconate, calcium lactose, calcium citrate and calcium acetate can be found in plants.

Studies have shown that both, organic and inorganic calcium can be absorbed by a human body with the same efficiency. This is also the case for any other mineral named below.

Recommended Intake Adults [mg/day]
Average Content In Bottled Water [mg/L]
What Does It Do In Your Body
Calcium1000-120030builds and maintains strong bones, it’s used to send nerve signals, release hormones like insulin and regulate how muscles and blood vessels contract and dilate
Magnesium320-42010forms part of bone and muscle, playing a role in protein synthesis, nerve transmission and muscular contraction/relaxation
Potassium3500-47000-1it is involved in muscle contractions, heart function and managing water balance
Sodium500-10008along with maintaining normal fluid balance, it plays a key role in normal nerve and muscle function
Chloride23009It is needed for fluid regulation and electrolyte balance

Why does water taste?

Before talking about what makes water taste in one way or the other we have a look at what TDS and pH value can tell us about the waters taste.

As seen above if water has a pH lower than 7 it will be acidic and acidic substances tend to have a sour taste. That makes sense, right? Lemons are sour. Alkaline substances tend to have a bitter taste.

As for the TDS, higher TDS water have a heavier taste and a much more prominent “mouthfeel,” a term used by water connoisseurs to describe the overall sensory impression. The mouthfeel may include slight saltiness where there is an appreciable Sodium content in the water. Lower TDS water, particularly those with the very lowest TDS, have virtually no taste, and “express” an airy or light mouthfeel. Consumers describe the lowest TDS waters as tasting clean, with even a hint of sweetness.

Generally is the taste strongly depending on the kind of mineral combination and content in the water. The TDS itself does not tell us what minerals are in the water only how many. Calcium makes water taste milky and smooth, magnesium can be bitter, and sodium makes it taste salty.

Buildings with old pipes could be rusty or result in excess trace minerals in your water. Thus, you might experience a metallic taste, or even a salty taste, from your tap water.

Lastly, since water has a neutral pH, it will pick up on any taste you previously had in your mouth. For example, if you eat something sour, your saliva produces chemicals that trigger a sweet-tasting sensation. If you then take a drink of water, it may taste slightly sweet. Your body can even confuse the senses of taste and smell, associating a taste with something you’re actually smelling.

So, while the purest form of water probably doesn’t really have much of a taste, there are many factors that change that, even if just slightly, along the delivery path to you, right down to your body’s perception when it hits your mouth.


The trace mineral content of water is very small compared to the daily need we have for them so you are better of supplying those through a healthy and diverse diet. Where the mineral content in water plays a bigger role is in the taste of water. If you grab a bottle of your favourite water check the mineral content on the label and you know what mineral combination you prefer.

Osmosys offers 3 different taste profiles from low to high mineral content so you can experience your favourite tasting water right from your kitchen tap instead of shopping expensive plastic bottles and carry them all the way home. Have a look here for more information.

Contamination in your tap water