The pH level of drinking water reflects how acidic it is. PH is measured on a scale of 0 to 14, with 7 considered neutral, meaning there’s a balance between the water’s acidity and basicity.

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In 1994, Denver Water and state health officials determined that raising the pH of tap water could reduce its corrosive power, thereby reducing the likelihood of lead getting into water as it passes through customer-owned water service lines, household plumbing and faucets that contain lead.

• For years, the water Denver Water delivered to customers had a pH that ranged between 7.5 to 8.5, with a target of 7.8. Now, Denver Water's pH range is between 8.5 and 9.2, with a target of 8.8. This was done as part of the Lead Reduction Program, which was approved by state and federal health officials.

The pH level of drinking water varies based on a variety of factors, including the source of the water and the treatment steps that are needed. Increasing the pH of water is a proven technique used by many water utilities to protect customers from the likelihood of lead or other metals getting into drinking water.

In Colorado, state health officials say that among water systems that serve more than 50,000 people, the City of Westminster, under the guidance of the Colorado Department of Public Health and Environment, has maintained a pH of about 8.5 to 8.6 in its drinking water for the last six years.

Other cities that adjust the pH of their water to levels above 8 on the pH scale include:

• The Massachusetts Water Resources Authority, which serves 3.1 million people in 61 communities including Boston, adjusts its water to a pH of about 9.0 to 9.5. The authority says the adjustment “helps to reduce the potential that water will leach metal that might be in your household plumbing.”
• The city of Ottawa, Canada, which serves about 900,000 residential, commercial and industrial customers, adjusts its water to a pH that is between 9.2 and 9.4 “to minimize the amount of lead and other metals that can dissolve into tap water.”
• The San Francisco Public Utilities Commission, which serves 2.7 million residential, industrial and commercial customers in the city and 27 suburban agencies, adjusts the pH of the water throughout the year in a range from 7.8 to 9.9, with an average of 9.4, as the sources of the city’s water supply change.

Officials with the Colorado Department of Public Health and Environment say there are no health concerns about drinking water with pH levels at 8.8, Denver Water’s current target on the pH scale.

Some bottled water has a higher pH and is marketed as alkaline water, which proponents say has health benefits. But the Mayo Clinic says more research is needed to verify these claims.

Denver Water has been and continues using sodium hydroxide, also known as lye or caustic soda, to raise the pH of the water. This inorganic compound also is used to make soap and paper.

Increasing the pH is part of Denver Water’s Lead Reduction Program, approved by health officials at the Colorado Department of Public Health and Environment and the Environmental Protection Agency in December 2019. The program also includes replacing an estimated 64,000 to 84,000 customer-owned lead service lines with copper lines and providing customers with water pitchers and filters certified to remove lead from drinking water. This is being done at no direct cost to the customer.

Denver Water raised the pH of the drinking water to the new target range during the first week of March 2020.

Since the mid-1990s, Denver Water has adjusted the pH of the water it delivers to customers to reduce the risk of lead and other metals from getting into drinking water. Prior to March 2020, the pH ranged between 7.5 and 8.5, with a target of 7.8. Now, the pH ranges between 8.5 and 9.2, with a target of 8.8.

The water Denver Water delivers to customers is lead-free, but lead can get into the water as it passes through lead-containing customer-owned water service lines that connect homes to Denver Water’s main delivery pipe in the street (lead service lines are more likely if the home was built prior to 1951), the solder that connects sections of pipe in their home (if installed prior to 1987) and faucet parts (if made prior to 2014).

Learn more about the sources of lead in drinking water.

Raising the pH of drinking water makes the water less corrosive. This change also strengthens an existing protective coating on the interior of the pipe. The coating reduces the likelihood of lead getting into the water as it passes through customer-owned water service lines, household plumbing and faucets that contain lead.

Denver Water has information on the sources of lead in drinking water as well as its Lead Reduction Program that will protect our customers and future generations from the risk of lead in drinking water.

The Lead Reduction Program, including the pH increase, was approved by both the EPA and CDPHE after thorough study of how the change would impact Denver’s water system and the quality of the water. Raising the pH of the drinking water doesn't affect its taste or odor. You may have noticed that the water feels more “slippery.”

Denver Water has been and continues working with irrigation and landscape experts locally and nationwide to learn more about potential impacts from the pH increase. It is important to recognize that water pH and soil pH, while related, are different.

The feedback we’re hearing so far, from scientists and experts in other cities where the water has a higher pH level, is that in general there should not be any major impacts on plants and landscapes, especially when best management practices are used. For example, when sprinklers are used to irrigate, pH levels in the water drop as the water is exposed to carbon dioxide in the air. Partners are also looking into soil amendments for trees to account for pH adjustments.

Denver Water continues to work with partners in Colorado and around the U.S. to learn more about their experiences with higher pH levels. Several utilities, including one in the Denver-metro area, have been operating within this pH range for many years, and we are hopeful the information they have will provide a valuable resource for our community and our partners. As new information becomes available, Denver Water will update these FAQs. 

Regarding nonpotable recycled water used for irrigation purposes: The recycled water provided by Denver Water via purple pipes and used in cooling towers and for irrigation purposes remains safe for intended purposes. This water has been cleaned twice, once at the Metro Wastewater Reclamation District facility and a second time at Denver Water’s Recycling Plant. The change in pH levels is not expected to significantly affect the quality of the water produced. 

More information about Denver Water’s recycled water program is available here. 

What about trees?

Denver Water recognizes that trees provide benefits to the community. It will be important in coming decades that the community as a whole look at the health of our urban canopy in a holistic manner, taking into account factors such as climate change, variability in precipitation, disease and water quality, including the change in pH. We have been and will continue taking steps to work on these issues in partnership with experts in the landscape industry, academia and public parks and forestry departments. 

Since 2013, Denver Water has participated in a research study on trees and soil health, partnering with the Denver Parks Department and Colorado State University to monitor tree tissue health and water quality impacts on soil. This monitoring program takes place at more than 300 sites across our service area. The study’s most recent report can be found here. 

This ongoing research effort will provide Denver Water, our partners and the public with information on a range of issues affecting our city’s landscapes. We will continue these partnerships and studies to help landscape and tree experts develop and implement best management practices.

Technical Information 

The chart below provides information on projected changes in Denver Water’s water chemistry, based on the years of study that took place before the Lead Reduction Program was approved. Note, this information is about water quality only, and as such is not indicative of changes that may or may not occur in soil irrigated with Denver’s water.

The chart below reflects the range of actual water quality measurements in Denver Water’s system prior to the March 2020 increase in pH and the projected ranges following the increase. While this information is specific to water, it may be helpful to experts evaluating other factors influencing plant health, such as soil.

Regarding sodium levels indicated on the chart, the Environmental Protection Agency since 2003 has recommended utilities reduce sodium levels to between 30 milligrams per liter and 60 milligrams per liter to avoid being perceived as tasting “salty.” Denver Water’s sodium levels have been below those levels and are projected to remain so. 

Denver Water also is sharing this water quality information with soil and plant experts who can use their expertise to offer guidance on potential best management practices. 

You should consult with your veterinarian or local fish or aquarium store for guidance. But experts at Colorado State University indicate there hasn’t been a lot of research on pH levels in water impacting pets.

For fish, different kinds of fish prefer different ranges of pH. For instance, freshwater fish, in general, prefer a lower pH than saltwater fish.

Experts at Colorado State University say it’s a good practice to regularly test the pH of the water in the fish tank and also to test and adjust the water if needed prior to adding it to the tank.

Fish store operators in the Denver area indicate there are steps that can be taken to lower the pH of the water, if needed, such as introducing a piece of driftwood, adding peat moss to a filtration system or adding a chemical to reduce the pH.

An increase of pH of the water used in brewing operations can affect the process of crafting beer or spirits. Homebrewers should ask their local homebrew shop for suggestions on appropriate products to reduce pH.

Breweries and distilleries typically have their own procedures for testing and adjusting water used in their operations and should continue to follow those procedures. The Colorado Brewers Guild recommends that Denver brewers acquire an independent water analysis of their brewing water to evaluate the specific impact.

Denver Water’s website has additional information useful to brewers and distillers available. This information has been updated following the change in pH.

This change in pH in general increases the amount of “scaling” on equipment — the white mineral deposits that can be seen after water has dried. The pH increase also increases the alkalinity of the water. The water Denver Water delivers is typically at or above 40mg/L as CaCO3.

This increase in pH may affect the operations and/or maintenance procedures of your business or equipment. You should consult the manufacturer or operator of the equipment.

Regarding dialysis equipment, Denver Water contacted DaVita, which as of December 2019 provided dialysis services to more than 235,000 patients in the U.S. and 10 other countries. DaVita said the pH change for Denver Water’s service area poses no risk to dialysis patients and will not affect in-center or home dialysis treatment operations. More information on water quality in dialysis is available on DaVita’s website.

Denver Water’s new, higher pH target of 8.8 does not change the hardness of the water. You may notice a small amount of additional scale develop over time where hot water is in contact with fixtures and appliances, such as hot water heaters, dishwashers and showerheads. Follow the manufacturers’ directions for care and maintenance of these appliances.

Adding a water softener to your home should be approached with caution because softeners add sodium to the environment, which can affect the health of plants, animals and people who live downstream of us. It also can undo protective benefits the higher pH level has on household plumbing that may contain lead. Learn more about sources of lead.

Denver Water’s pH levels will remain at the target of 8.8 on the pH scale at least until after the estimated 64,000 to 84,000 lead service lines in our system are replaced through the Lead Reduction Program. This is expected to take 15 years.

However, Denver Water is not able to automatically reduce the pH levels back to pre-Lead Reduction Program levels after the lead service lines are removed in 15 years. Once that work is complete, any change in water quality must be studied thoroughly to ensure public safety before implementation. It took several years of study, review and discussion for experts and scientists at the Environmental Protection Agency, the Colorado Department of Public Health and Environment and Denver Water to decide that the Lead Reduction Program was the best path forward to reduce the risk of lead getting into drinking water. 

Also, while replacing a lead service line removes the primary source of lead in drinking water, it doesn’t address other potential sources of lead in drinking water. Lead solder was commonly used to connect copper water pipes in homes and buildings until Congress banned the use of lead solder in 1987. Faucets and faucet parts made before 2014 also contain higher levels of lead. 

Having a pH target of 8.8 for the water we deliver to customers protects all our customers from the risk of lead getting into drinking water from all these sources.