Drinking Water Quality: What You Need to Know

How can we know the water quality we have in the taps of our homes, buildings, workplaces, schools, hotels, restaurants, cities, etc. If I request it from a lab, what should a potability analysis include? How much is it going to cost me? Here we will try to resolve all these issues.



A phrase I read in some book that I do not now remember comes to mind: “The essential is invisible to the eyes.”

The quality of the water we drink is essential to our lives and invisible to the eyes.

And that “invisibility” creates uncertainty and derecognise among consumers.

And that uncertainty and derecognise creates business opportunities for many companies that take advantage of the situation.

With this article, I have set out to help all people who doubt their taps’ water quality by providing several concepts, ideas, and practical tools to clear those doubts.




A “drinkable” or“human-friendly” quality water is water that poses no health risk.

One of the global references in this field is WHO (World Health Organization), which sets the maximum allowable concentrations of the water’s different substances to be drinkable.

Another reference in this field is the EPA (Environmental Protection Agency) of the United States, whose water quality standards are higher than the vast majority of countries.

Each country has its own water quality legislation for human consumption, but almost all follow WHO guidelines when setting benchmarks.


This Royal Decree 140/2003 defines Water for Human Consumption verbatim as:

(a) All those waters, whether in their original state, either after treatment, used for drinking, cooking, preparing food, personal hygiene and for other domestic uses, whatever their origin and regardless of whether they are supplied to the consumer, through public or private distribution networks, cisterns, public or private warehouses.

For this Royal Decree, water for human consumption shall be safe and clean when it does not contain any microorganism, parasite or substance, in an amount or concentration which may pose a risk to human health.

In this law, ordinary citizens are often lost, as they are often difficult to interpret and generally dense reading.

The important thing as a first step is to know what law regulates our country’s water quality.

So far, the concepts and definitions. Now let’s see what things you can do to know the water quality of your faucet.




First of all, the first thing is to inform yourself well of the origin of my water and to be clear what the critical parameters that may affect water quality may be:

  • Does my water come from a network operated by a supply company?
  • Is it a serious company? What treatments do you use?
  • Does my water come from a well?
  • Is my water stored in a pre-consumption reservoir?
  • Have there been any events in the area, spillage, neighbourhood complaints or any alarms that will make you doubt?



Request up-to-date analysis from my sourcing company and my city council; search public bodies such as the Ministry of Health, Environment or the like; search for literature on specialized websites, such as environmental organizations.




IDEAL: Request a water quality analysis from a private laboratory.

It’s the only way to be sure of the quality of the water coming out of your faucet.

Your water company can give you an analysis of the overall quality of the water they supply. Still, through the supply pipes and its indoor facilities, the water can lose quality and suffer some pollution potentially harmful to your health.

Another option, less advisable, but that can be valid in very particular cases is to analyze the water yourself.

Next, let’s look at these 3 points in more detail.

*If you need advice on your water quality, you can write to me through the Ecosocial Water CONTACT FORM and tell me your case.

**I remind you that all Ecosocial Water subscribers have a free first consultation.



Knowing where the water that reaches your taps comes from is critical.

We should know the path that runs from the natural source of capture (rivers, lakes, wells, etc.) to your tap and clear about all the intermediate elements.

Sometimes water can come from less typical sources, such as rainwater or seawater (desalination).

A typical path might be:


Today, the vast majority of people live in populations with a supply network.

In this case, the first thing would be to know if the water passes through a treatment plant, also known as ETAP (Potable Water Treatment Station).

This is the most common cause, although there are scattered communities that receive water without any treatment in many parts of the world.

*If you find it interesting, I can write a specific article about the whole process in an ETAP to water. You can tell me below in the comments.

The next thing would be to identify the company that operates the water treatment plant (ETAP) and supply the water.

It’s as easy as looking at the water bill. (there should be all the company data).

We should research online, talk to neighbours, or contact local experts or environmental groups to determine if any threats could jeopardize the area’s water quality.

Some examples of possible threats:

  • nearby industry that pours its wastewater without purification.
  • A river contaminated by sewage from upstream villages.
  • Groundwater contaminated by agro toxins (pesticides, chemical fertilizers…).
  • Natural contaminants present in the geology of the area (example: arsenic).
  • Treatment deficiencies/supply network (example: trihalomethanes).
  • Well, water contaminated by faecal pathogens in populations without sewerage.

The vast majority of companies operating hydraulic infrastructures deliver higher quality water than standards and are continuously monitoring and analyzing the entire process as they must comply with stringent legislation.

Therefore, before you hesitate, know well because your tap’s water quality is most safe is suitable for human consumption.

Look, because a lot of times the problem is inside the house. An example is cisterns or elevated tanks, where water quality can be altered if we do not perform regular cleaning and maintenance care.



After searching for general information after the previous stage, we can dig a little deeper and try to search for recent water quality analyses of the area or associated reports that tell us what type of water we have.

Where do I start?

  1. Website of the company operating the supply network (they usually have quality data published on their website). If not published online, they should provide it to any subscribers to the service on request, particularly if they are a public company.
  2. Websites of public bodies, such as the City Council, the Ministry (Health or Environment), etc.



Taking advantage of as a first example a consultation of a reader, in the following links, you can see the quality of the water that is in the city of Valladolid:

For those who don’t have technical notions of the subject, seeing a water quality analysis may seem Mandarin Chinese. I know.

But, following Valladolid’s example, anyone who reads these reports can conclude that water is suitable for consumption. There is no parameter of those analyzed that exceeds the limit values established.

second example, to exercise caution:

You have to be careful with some water companies’ websites, as they are often not entirely transparent and are more concerned with their image than people.

Let’s look at this with an example of a supply with Water not suitable for human consumption:

L’Eliana (in Valencia).

«The consumer water that reaches homes is of absolute confidence because it more than meets all the strictest requirements and controls required by DR. 140/2003 which are set by the health authorities of our country, the European Union and the World Health Organization.”

They include a pdf analysis (Full Eliana Network Analysis), where it is observed that the nitrate concentration is higher than established.

In short: caution with some companies’ information. It needs to be contrasted with public data and neutral entities.

*UPDATE: The previous example of L’Eliana was solved at the end of 2022 by a denitrifying plant that delivers water to the population below 50 mg/l of nitrates. Still, the example was valid for a long time and shows that such situations of unsewn information can happen.



Looking at the extent of this article and the number of important things I want to tell you at this point, it is best to finish here and dedicate a blog post specifically to Water Analysis.

Maybe you’re already one step ahead and what you’re thinking is installing a filter to drink your tap water safely and without having to buy more bottled water.

If so, I have this post posted that has already helped a lot of people:

As always, I could have helped you. If you liked this post’s content, you could easily share it by clicking on the social media buttons.

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Dr. Med. Raoul Hasert is a specialist in dermatology and venereology. He is a senior physician in Praxisklinik Dr. Hasert.

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