pH value of tap water: what is normal?

Reading time: ~13 minutes

What exactly is the pH value of water?

The pH value indicates how acidic or how alkaline a liquid is. The scale runs from 0 to 14, where 7 is exactly neutral. Everything below 7 is acidic, everything above 7 is alkaline. Tap water almost always sits just above that 7, and that is no coincidence but a deliberate choice by your water utility.

One thing is often overlooked: the pH scale is logarithmic. A step from pH 8 to pH 7 means ten times as many hydrogen ions, and from 8 to 6 already a hundred times as many. A difference of half a pH unit on your test strip is therefore not a detail, even though it looks small on paper.

More importantly: a tidy pH says nothing about what else is in your water. PFAS, microplastics, medication residues and heavy metals do not change the acidity level in a measurable way. Anyone who wants to know what is really in their glass looks at the water quality data of their own water utility rather than a pH strip.

What pH value does Dutch tap water have?

The legal range is set out in the Dutch Drinking Water Decree (Drinkwaterbesluit). Vitens summarises it in its glossary as 7.0 less than pH less than 9.5, noting that the optimal pH for preventing corrosion lies between 7.8 and 8.3. Brabant Water uses exactly the same split on its water quality pages: 7 to 9.5 is the standard, 7.8 to 8.3 is optimal.

Those legal requirements did not come out of nowhere. The RIVM explains that legal quality requirements have been set for drinking water covering roughly 80 chemical substances and substance groups and micro-organisms, including indicators for odour, taste and other physical parameters. The pH belongs to that last group: an indicator that guides operations.

That last figure is useful as a reference point. In Eindhoven, Brabant Water reports an acidity level of 7.65 to 8.13 and a hardness of 5.71 to 6.16 degrees German hardness. That is exactly the picture you see across most of the Netherlands: slightly alkaline water, neatly in the middle of the legal margin.

At PureFilter, we get this question remarkably often from people who have just bought a pH meter and are startled by a reading of 8.1. That is not an anomaly, that is the intention. The common misconception is that "neutral" water would be the goal. It is not: perfectly neutral water at pH 7.0 sits at the lower edge of the standard and is technically actually less desirable.

Why do water utilities aim for 7.8 to 8.3?

The reason is neither taste nor health, but metal. The lower the pH, the more aggressively water behaves toward the materials it flows past.

1. Lead and copper dissolve faster at a low pH

Vitens is explicit about this: the amount of lead that dissolves in drinking water depends on the acidity level, the temperature, the hardness and the length of time the water has stood still in lead household pipes. The standard for lead in the Drinkwaterbesluit is a maximum of 5 micrograms per litre, measured at the main tap. The homeowner is responsible for the household pipes in their own home. If you live in a building from before 1960, that is not a theoretical point; we have covered it in our article on filtering lead out of tap water.

2. Bicarbonate keeps the pH stable

A second reason is buffering capacity. Vitens sets a lower limit for bicarbonate of more than 60 milligrams per litre and literally adds: if there is enough bicarbonate in the water, less copper and lead can be taken up. That same buffer system ensures the pH in the pipe network does not swing back and forth. Vitens also mentions a threshold for total inorganic carbon content of at least 24 milligrams per litre, precisely to prevent large pH fluctuations.

3. The pH is actively adjusted with CO2

The third point surprises many people: the acidity level of your tap water is partly manufactured. According to Vitens, carbon dioxide is a weak acid that partly determines the acidity level and thus the taste of the water, and depending on the groundwater, the utility artificially adds CO2 to bring the water to the right taste. The pH value you measure is therefore a controlled value, not a natural given.

Does the pH value differ by region?

Yes, but less than you might think. All Dutch water utilities operate within the same legal margin and aim for the same optimum, so the differences between provinces are small. What does vary strongly is the hardness of the water, and the two are regularly confused with each other.

Hardness is something different from acidity level. Vitens defines hardness as the amount of calcium and magnesium in the water, with a legal lower limit of more than 1 millimole per litre, equal to 5.6 degrees German hardness. High hardness means a lot of limescale, not automatically a high pH. If you want to know how hard the water is where you live, you can find that per location in our overview of water hardness per municipality.

The most reliable source for your own pH is the water quality page of your water utility. Brabant Water publishes the acidity level and hardness per location, plus quarterly updated PDFs with the full composition per production site. Vitens offers the same through a postcode check. That is more accurate than any national estimate, and it takes you half a minute.

Why groundwater and surface water differ

Part of the regional difference comes from the source. According to Vitens, groundwater has a constant temperature of 10 to 12 degrees Celsius and a stable composition; surface water fluctuates more with the season. Dune water and groundwater are naturally rich in limescale, while water utilities soften the water centrally almost everywhere when the raw hardness is high. The end result at the tap is therefore closer together than the sources themselves.

Is a too high or too low pH harmful?

Within the Dutch standard: no. The WHO addresses pH in its guidelines for drinking-water quality and sets no health-based guideline value for it. The reason is that pH at normal drinking-water values has no direct effect on the consumer, but is one of the most important parameters for operations: it determines how well disinfection works and how strongly pipes are attacked.

That does not mean pH is irrelevant everywhere. There are three situations where the value genuinely matters:

• Structurally below 7.0: then the water becomes more aggressive toward copper and lead. This falls outside the legal standard and should be reported to your water utility.
• Old household pipes: the combination of a lower pH and long-standing water in lead or copper pipes produces the highest metal release. Flushing helps, replacing helps more.
• After a filter step that removes minerals: we will come back to this shortly, since this is exactly where most of the confusion lies.

And the claims around alkaline water?

All kinds of health promises circulate around "alkaline water" with a pH of 9 or higher. We do not take part in that, and the reason is simple: there is no health-based guideline value for pH because the body regulates its own acidity level itself. Your stomach produces hydrochloric acid, and your blood is kept within a very narrow range by your lungs and kidneys, regardless of what you drink. Buying a filter to make your blood "more alkaline" is therefore not a good reason. Buying a filter because you want to remove PFAS, microplastics or heavy metals from your water is.

What does a water filter do to the pH value?

This is the one point in this entire topic that genuinely makes a commercial difference, and it is rarely explained well. Different filter techniques do something very different with the acidity level.

Reverse osmosis lowers the pH

A reverse-osmosis system pushes water through a very fine membrane and retains almost everything in the process, including dissolved minerals and bicarbonate. And it is precisely that bicarbonate that, according to Vitens, provides the water's buffering capacity. Remove the buffer and there is nothing left to hold the pH in place, so the value drops. That is why almost every serious osmosis system has a remineralisation filter behind it: without that step the water is too poor in minerals and too aggressive for pipes. We explain what that means for your daily glass of water in our article on whether osmosis water is healthy or unhealthy.

Activated carbon leaves the pH virtually untouched

An activated-carbon block works through adsorption: substances attach themselves to the enormous internal surface of the carbon. Dissolved minerals and bicarbonate simply pass through. The pH therefore stays roughly equal to that of your tap water. That is an advantage, not a shortcoming: the buffer your water utility carefully set remains intact.

Mineralisation counters that

The PureFilter Mineral+ works in five steps and deliberately places mineralisation as the last step. Purification happens first, then calcium, magnesium and potassium are given back via Swedish Mineral Rock™. That is not a trick to artificially boost the pH, but the way to prevent your water from losing its mineral profile. The filter is NSF-certified to standards 42, 53, 61 and 372 and removes more than 100 contaminants, including PFAS, microplastics, heavy metals, medication residues and chlorine. It is explicitly not reverse osmosis. We explain how many minerals you actually want in your drinking water in our article on minerals in drinking water.

If you are unsure which technique suits your situation, the overview in which we explain per filter type which filter type leaves your water's mineral balance intact can help. That is often the crux of the choice when it comes to a pH question.

Comparison: filter techniques and their effect on pH

The row that surprises most people is the last one. A softener tackles limescale and does nothing about PFAS, microplastics or medication residues. That is why we do not sell them. If you only want less limescale build-up, read why filtering limescale out of tap water is a different question from water purification.

What it costs

The PureFilter Mineral+ costs €149.00 including the first filter. A single replacement filter costs €65.00 and the duo with two cartridges €115.00. Converted over the 15,000 to 20,000 litres a cartridge can handle, that works out to less than one cent per litre, compared with €0.40 to €1.00 for a litre of bottled water. How long a filter lasts depends on household size: for 1 to 3 people around twelve months, for 4 to 6 people around six months. If you would rather not have to think about it, the Filter Plan automatically sends you a new one on time for €48.00 or €86.00 per delivery. Individual filters remain available to order separately. You can find the full overview at our filters for household drinking water.

Measuring the pH value of your tap water yourself

Measuring it yourself is possible, but do it properly, otherwise you are mainly measuring your own measurement error. There are two routes.

Test strips

Strips work with a colour reaction and give a rough indication. They are cheap and quick, but the reading is subjective and the distinction between pH 7.5 and pH 8.0 is hard to make with the naked eye. For the question "am I roughly where I should be", it is sufficient.

Digital pH meter

An electronic meter is more accurate, but only if you calibrate it with buffer solutions. An uncalibrated meter that has sat dry in a drawer for months will confidently give you a wrong number.

If you see white or milky water when tapping, wait a moment before measuring. Vitens points out that tap water with a lot of oxygen briefly looks whitish and that this clears up on its own. We explain exactly what happens there in our article on white water from the tap.

pH, taste, coffee and limescale

Acidity level is directly linked to how water tastes. Vitens says so itself: carbon dioxide is a weak acid that partly determines the acidity level and therefore also the taste of the water, and the utility adds CO2 to bring the water to the right taste. Anyone who finds their water tastes "flat" is therefore often not tasting a problem but a setting.

For coffee and tea, composition counts more heavily than pH alone. Limescale and minerals determine how aromas are extracted from the coffee and how quickly your machine scales up. In hard water that goes wrong faster than in soft water. Anyone who cares about their machine should read our article on the water filter for a coffee machine, since that is where the practical difference lies.

One more detail that is often forgotten: the pH you measure can differ from the pH your water utility supplies. Water that stands overnight in your own pipes loses CO2 to the pipe wall and becomes slightly more alkaline as a result. That is not a fault of your water utility and no reason for concern; it is the reason flushing before measuring appears in every protocol.

Frequently asked questions

Conclusion

The pH value of tap water in the Netherlands is legally required to be between 7.0 and 9.5, and water utilities aim for 7.8 to 8.3 within that margin. Your tap water is therefore slightly alkaline, and that is exactly the intention: that value protects pipes against corrosion and keeps lead and copper where they belong. The WHO sets no health-based guideline value for it, because pH at normal drinking-water values poses no health risk.

What the pH does not tell you is what else is in your water. Acidity level and purity are two different things. If you want to be sure that PFAS, microplastics, medication residues and heavy metals are removed, choose based on certification, not on a number from a test strip.

That is also where the difference between filter techniques lies. Reverse osmosis removes the minerals and the buffer and thereby lowers the pH; the PureFilter Mineral+ purifies first and then gives back calcium, magnesium and potassium via Swedish Mineral Rock™. The filter costs €149.00 including the first filter, is NSF-certified to standards 42, 53, 61 and 372, removes more than 100 contaminants and is installed in 5 to 10 minutes without a plumber, using a single pipe wrench. You swap the cartridge later using the included key. Anyone who prefers to compare first can look at the filter that adds minerals back alongside the other options. With 40 days of free returns and a 5-year warranty, you can calmly find out at home whether you taste the difference.