Why TDS fails to be a good way to measure water quality in Malta

Why TDS fails to be a good way to measure water quality in Malta

Total Dissolved Solids (TDS) is used by Reverse Osmosis suppliers in Malta as a way of demonstrating the effectiveness of water filters, however it really does fail as a good way to measure water quality in Malta.

In this article we explain what  a TDS meter measures, and more importantly what it does not test.

A TDS meter is used as a water testing method as it is cheap and easy to do. I bought a TDS tester to try out for less than €20 in Malta and it was really easy to use, just place the probe end in water and bingo you have a TDS number.

The issue is that TDS is very limited in terms of what it is measuring. Sure, it has it's uses but it is just one measure of one factor in water quality so it is really failing to give you a complete picture of water quality in Malta.

On the other hand a full detailed analysis of water quality was at least €1,000 when we had our independent test results completed for Malta water filtration with TAPP Water.

What are Total Dissolved Solids (TDS) in water?

We can start by knowing what TDS is and what it is measuring. Total Dissolved Solids are the inorganic salts and small amounts of organic matter that are dissolved in water. So really a TDS meter measures the electrical conductivity of salts and minerals in water and then calculates a TDS number.

The Total Dissolved Solids (TDS) are measured in mg per Litre unit of water (mg/L) which is also known as parts per million, ppm. That's why a TDS meter is sometimes called a PPM meter.

The following are included in measuring Total Dissolved Solids (TDS) in Malta:

  • calcium
  • magnesium
  • sodium
  • potassium
  • carbonate
  • bicarbonate
  • chloride
  • nitrate 

So from all these that are measured the only contaminants are nitrates and chloride, the rest are all healthy minerals.

A TDS meter does  not tell you if your water is healthy, for instance high levels of contaminants such as THM's, PFAS Forever Chemicals, lead and heavy metals, oil, arsenic, pesticides, herbicides and pharmaceuticals can b present in your water with a low TDS level , which is not an indicator of water quality, its an indicator of low dissolved salts and minerals.

What is a good measure of TDS in tap water?

Typically tap water in Malta has a TDS measure of up to 1,000 mg/L which is quite normal for Malta. Water Services Corporation provide test results all over Malta of the conductivity which can then be used to calculate TDS. This exactly what a TDS meter does, it measures the conductivity of water and then calculates TDS.

TDS Water testing in Malta

Areas with higher quantities of minerals in water will have higher readings.

Reverse Osmosis, ion exchange and distillation water filtration systems will reduce this measure to zero or close to zero. Activated carbon filters will not filter out TDS and with a TAPP Water Filter we do not expect conductivity, and hence TDS to change, as all healthy minerals are retained. Nitrates and Chlorine are filtered out though which reduces TDS potentially but not enough to show up as a drastically reduced reading.

Bottled mineral water will measure high in TDS, for example Evian comes in at 300 mg/L and San Pelligrino at 850mg/L; we would aspire to drink such healthy mineral waters and trust them to be doing us good, regardless of their TDS measure.

The medical importance of mineral waters depends on the contained amount of minerals and trace elements. Calcium and magnesium in mineral waters are of greatest interest with respect to their potential relevance for the health status; iodine, fluorine and lithium are the most important trace elements. The bioavailability of minerals from mineral water is good and can be compared with the values derived from milk. A positive effect of the minerals in mineral water on health status is especially apparent in the case of insufficient intake by nutrition. The apprehension that there might be an undesired hypertensinogenic effect due to the sodium content in mineral waters is not justified. Sodium is present in mineral water in small amounts only, and mainly as sodium bicarbonate, which has no effect on blood pressure. A certain advantage of a delivery of minerals and trace elements by regular drinking of mineral waters is the simultaneous intake of water, without supply of energy. [Health-related effects of natural mineral waters]

Is a high Total Disolved Solids (TDS) measure a bad thing?

A study by the World Health Organization concluded with the following measures in their Guidelines for drinking water:

  • 50 mg/L to 300mg/L - Excellent
  • 300 mg/L to 600 mg/L - Good
  • 600 mg/L to 900 mg/L - Fair
  • 900 mg/L to 1200 mg/L - Poor
  • 1200 mg/L and above - Unacceptable

Higher TDS waters are described by testers as having a heavier feel to them with very low TDS waters being described as flat, but it is not a question of water quality, more about taste and feel.

Why do people use TDS as a measure of water quality in Malta?

The simple answer is that its cheap and easy to do. Just purchase a €20 tester, drop it in a sample before and after filtration and you have an immediate "answer". But it's not a great answer and not accurate as a measure of water quality.

This measure is particularly used by Reverse Osmosis companies to promote the use of this filtration system in Malta; but there are disadvantages too for this type of home water filtration system in Malta which we describe in our article All about Reverse Osmoisis (RO) home water filters in Malta.

Real tests of water quality focus on the levels of chlorine, pesticides, heavy metals and pharmaceuticals and these require far more analysis and complex testing equipment.

TAPP Water filters have been tested for TDS in tap water with values up to 1000 and the water taste remains good and the water is safe to drink.


Unless your tap water as a TDS value that is vastly outside of the recommended range you have no need to worry. High TDS in your Malta tap water basically means that there is mineral water coming out of your tap. Once you have filtered it to remove over 80+ common contaminants in Malta tap water with your TAPP 2 Twist you will be really happy.

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