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• 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 how acidic or basic the water is.
• Denver Water has been adjusting the pH of water since the mid-1990s. A higher pH creates a protective coating on the interior of the pipe, which 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.
• As part of the Lead Reduction Program, Denver Water increased the pH of the water it provides in March 2020, strengthening the existing protective coating on the interior of the pipe.
• Since this change, lead levels have dropped significantly according to regular tests of drinking water taken from faucets in customers’ homes that are known to have lead service lines.
• When Denver Water increased pH in spring 2020, test results from the 90th percentile of properties with known lead service lines showed a drop in lead levels from 12 to 6.1 parts per billion (the measurement for testing lead in water). By fall 2020, the levels within the 90th percentile dropped further to 4.1 ppb. Spring 2023 results dropped again to 3.5 ppb. Sampling at these types of properties has maintained an average below 4.0 ppb. The 90th percentile means that 90% of homes tested were at or below that value.

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.

• Denver Water has worked with irrigation and landscape experts locally and nationwide to learn more about potential impacts from the pH increase. It’s important to recognize that water pH and soil pH, while related, are different. 
• The feedback we’ve heard, 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 impact 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. Since the Lead Reduction Program started, we haven’t observed any noticeable impacts to trees/plants/grass as a result of the pH change. 

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.

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.