You may have heard of the term pH before. This term is commonly used to describe drinking water, but what exactly is pH?
The term pH stands for “potential of hydrogen” which, simply put, means how much free hydrogen there is in the substance. Regarding water, the pH describes how much hydrogen it contains. It seems simple enough, but why is this important?
pH works on a scale running from 0 up to 14, and water sits in the middle at ph7. At least, it is supposed to. When the pH shifts towards a lower value, the water is becoming acidic. But why does the pH of water change? Is it safe to drink acidic water?
What is the pH of water in the United States?
As mentioned, the pH of a substance refers to the amount of free hydrogen it contains and is a running scale from 0 up to 14. The most acidic substances such as hydrochloric acid will have a pH of 0, whereas very alkali substances such as drain cleaners and bleach will sit at around pH14.
Water is a neutral substance and sits at pH7, but there is variation in this across the United States and depending on the water source.
Freshwater varies considerably from place to place, whereas seawater has a pH of around 8. When it comes to drinking water, tap water is typically pH7.5 whereas bottled water ranges from pH6.5 – 7.5. 
The “safe” pH range for drinking water to sit in is pH6.5 – 8.5, although drinking water with a more alkali pH is not necessarily going to cause you any harm; it just might not taste or smell nice. The real problem is acidic water with a pH of 6.5
What causes acidic water?
If water is supposed to have a pH7, then what is causing drinking water to become acidic? The increased acidity can be down to both natural and man-made reasons.
The rocks making up the ground you live on have a significant impact on the pH of water. As the groundwater runs through the earth, the rocks it passes alter its pH.
Rock formations made from limestone naturally neutralize acid water, meaning we are more likely to have neutral water flowing out our taps. Other rocks, such as granite, do not.
Acid rain can also be produced by pollutants, particularly in large industrial areas. A study in the US carried out in 2002 looked at the pH of precipitation across the states, and they found that the rainwater ranged from pH6.3 down to an acidic pH4.1.
The northeast of the country generally has the most acid rain. Take a look at their results here. Acid rain can leak into groundwater and affect the pH of our drinking water.
How do I know if I have acidic water?
This is probably the next question you are asking: how do I know if I am drinking acidic water?
One of the first noticeable signs is finding blue-green stains in your sinks. Acidic water leaches metals such as copper, lead, and zinc from the pipes it passes through and can corrode away these pipes.
If you have iron pipes, the stains will be a reddish-brown color. These stains are a sign of metal corrosion. In fact, metallic tasting water can also be a sign of acidic water.
Low water pressure can be another sign. As the water is corroding the pipes it could be causing leaks and holes in your water systems which reduces the water pressure of your home.
What are the health risks of drinking acidic water?
Acidic water itself does not pose any major health risks. The main concerns are indirect effects of the acidic water from corroding the metal pipes and introducing metal compounds into the drinking water.
The biggest health concerns related to drinking acidic water are if that water has passed through copper pipes. Although beneficial in small doses, the continued short-term copper exposure can cause vomiting, nausea, diarrhea, and headaches.
Long-term exposure to copper through our water sources can lead to liver and kidney damage.
Lead pipes also propose a major concern. If the lead is corroded by the acidic water and enters your drinking water it can cause lead poisoning, which is especially damaging to young children.
Lead poisoning can increase the risk of cancers, strokes, kidney disease, and high blood pressure. In pregnant women, exposure to lead can result in stillbirths and miscarriages. 
The only real direct impact of drinking acidic water relates to dental health. Alongside leaching metal from pipes, acidic water leaches the minerals stored in our teeth and weakens the enamel. This predisposes our teeth to the cavity process and so makes dental health issues a lot more likely.
Alongside the health risks, both the metallic taste and the nasty stains caused by the leaching metals causes aesthetic problems and can make drinking water unenjoyable. Plumbing can also be corroded away and become damaged, so it is worth correcting the pH.
How can I test my water pH?
In the US, water quality is monitored by the US Environmental Protection Agency (EPA). However, they do not monitor pH levels directly as the preference for neutral water is seen as aesthetic, with all major health risks being down to secondary effects.
Local water supplies generally ensure water sits between the recommended pH range of 6.5 – 8.5, so home testing is not usually required. However, if you have notices metal staining or unpleasant tasting water, you may wish to carry out your own tests.
Home testing pH kits are readily available and affordable, and commonly sold for testing the pH of aquariums. Some of the most popular models are pH “pens” which have a digital display.
You simply collect a sample of your tap water, insert the pen, the pen does its thing, and a digital pH reading will be displayed.
If you want an external company to carry out testing, contact your local drinking water company. They will run a series of tests to look for contaminants and will try to solve the issue for you if their results are also worrying.
How can I treat acidic water?
If you have discovered your household has acidic water, do not fear! There are a couple of methods that can tackle acidic water.
1. pH Water Filters
The most common way is by using a pH water filter which neutralizes the water as it passes through. These typically use calcite as the neutralizing material.
As the water flows through the filter, the calcite is dissolved into the water and balances out the hydrogen ions. As pH is calculated using the free hydrogen content, the less free hydrogen ions, the higher the pH.
These filters are best at treating acidic water from pH5.5 or greater as it can increase pH by 1. For any water sources with a lower and more acidic pH, this method may not be effective.
A quick fix is to use a filter which also has magnesium oxide. This adds an extra edge to the rebalancing and can increase pH by 1.5.
There are also issues with calcite filters. The addition of calcite into water sources can make the water much harder, so you may also need to introduce a water softener.
The success of the filter is also significantly dependent on water flow through the filter. Moreover, too higher levels of magnesium oxide can increase the levels of magnesium ions and act as a laxative.
2. pH Balancing Injection Systems
The second option to treat acidic water is using pH balancing injection systems. A chemical pump will be fitted at the point of entry and will release alkali chemicals into your water to neutralize the ph. Sodium carbonate, more commonly known as Soda Ash is good for treating acidic water with pH4.5.
For people with highly acidic water with a pH of less than 4, then caustic soda is a better option for pH injection treatment. The chemical name for caustic soda is sodium hydroxide which is highly alkali with a pH of 14.
The alkali chemical neutralizes the acidic water, bringing it towards the neutral pH7. This should only be used as a last resort for very acidic water as it can easily overcompensate and leaving drinking water alkali.
pH balancing systems are more costly than pH balancing filters, but also do not alter the hardness of the water.
For more information on acidic water treatments, check out this video.
The take-home points
For most, tap water pH will fall within the “safe” range of pH6.5 – 8.5 and so acidic water will not be a concern. However, if you notice any signs of acidic water, carry out a home test and contact your local water company to find out the exact pH.
If your water is acidic, try using a pH balancing technique to treat the imbalance and restore fresh, neutral, pH7 water. Have you ever seen any signs of acidic water in your home? How did you go about treating acidic water? Let us know in the comments.