What is the pH scale?
The pH scale is a logarithmic measurement from 0 to 14 that indicates the acidity or alkalinity of a substance. A pH of 7 is neutral, while anything below 7 is acidic and anything above 7 is alkaline (or basic). Because the scale is logarithmic, each whole number increase or decrease represents a tenfold change in acidity or alkalinity. For instance, water with a pH of 8 is ten times more alkaline than neutral water with a pH of 7. While pure water has a neutral pH, the water found in your tap and natural sources can have a different pH due to dissolved minerals and environmental factors.
The recommended and unsafe ranges for pH in water
Determining how much is too much pH in water depends on the context, whether for drinking, household use, or aquatic life.
Drinking Water
The EPA sets secondary standards for drinking water, recommending a pH range of 6.5 to 8.5. Within this range, water is generally considered safe and aesthetically pleasing. A pH slightly above this, up to 9 or even 9.5, is often still safe, though it can cause taste issues and other aesthetic problems. However, extremely high alkalinity (equal to or greater than 12.5) is considered corrosive and hazardous.
Household Plumbing
Outside of the recommended 6.5 to 9.5 range, high pH levels can significantly damage your home’s plumbing.
- A pH > 8.5: Water with a high pH tends to be hard, leading to the formation of scale deposits. This scale can build up inside pipes, reducing water flow and decreasing the efficiency of appliances like water heaters and dishwashers.
- A pH < 6.5: Conversely, acidic water can corrode metal pipes, causing heavy metals like lead, copper, and zinc to leach into the water, which is a serious health hazard.
Aquatic Environments
Aquatic life is extremely sensitive to changes in water pH. The optimal range for most freshwater organisms is between 6.5 and 8.5.
- A pH > 9: Prolonged exposure to high pH levels above 9 can damage the gills, eyes, and skin of fish.
- A pH ≥ 10: Extremely high pH levels can be lethal to many aquatic species.
- Impact on Ammonia: In aquatic systems, a high pH also increases the toxicity of ammonia, posing a greater threat to fish.
Side effects of high pH water
While drinking water with a moderately high pH is not considered a health risk, it can cause several noticeable issues both aesthetically and functionally.
- Bitter Taste: Water with a high pH often has a bitter or soda-like taste, and can give your morning coffee a flat, unpleasant flavor.
- Slippery Feel: Alkaline water can feel slippery on the skin.
- Scale Buildup: A key indicator of high pH is the buildup of scale, which appears as white, chalky deposits on plumbing fixtures, shower doors, and dishes.
- Reduced Appliance Efficiency: Scale can obstruct water flow and hinder the performance of appliances, potentially leading to costly repairs.
- Interference with Disinfectants: High pH can decrease the effectiveness of disinfectants like chlorine, which can pose other indirect health risks.
High pH vs. Low pH: A comparison
| Feature | High pH (Alkaline) | Low pH (Acidic) |
|---|---|---|
| Taste | Bitter, soda-like, or soapy | Metallic or sour |
| Appearance | White, chalky scale deposits on surfaces | Blue-green stains on fixtures (copper) or reddish-brown (iron) |
| Plumbing Impact | Scale buildup clogs pipes and damages appliances | Corrodes pipes, leading to heavy metal leaching |
| Health Effects (Indirect) | May reduce effectiveness of disinfectants, potential GI irritation at very high levels | Potential for heavy metal toxicity from corroded pipes |
| Feel | Slippery | Not typically distinctive |
How to address high pH in water
If you have determined your water's pH is too high, there are several methods to correct it, depending on the severity and application.
Methods for the home
- Acid Injection System: For persistent, system-wide high pH, a chemical injection system can automatically add a controlled amount of acid (such as acetic acid) to the water supply to neutralize the alkalinity before it enters your home's plumbing.
- Reverse Osmosis (RO) Filters: RO systems are highly effective at purifying water and removing many contaminants, including the minerals that contribute to high pH.
- Ion Exchange Resins: Some water treatment systems use ion exchange resins to remove certain minerals and lower pH.
Simple, temporary fixes
- Add Acidic Substances: For drinking water, adding a small amount of lemon juice or vinegar can slightly lower the pH, but this should be used cautiously and is not a permanent solution.
- Use Natural Materials: In smaller, contained systems like aquariums, adding driftwood or peat moss can naturally lower the pH.
Conclusion
While the human body is remarkably good at regulating its own internal pH, extreme levels of alkalinity in water can cause problems for household plumbing and sensitive aquatic ecosystems. The EPA's aesthetic guideline of 6.5 to 8.5 provides a useful benchmark, but understanding the signs of high pH—like scale buildup, bitter taste, and appliance inefficiency—is key to knowing when to take action. Testing your water is the first step, followed by implementing the appropriate correction method, whether through a whole-house system or a simple filter. This ensures that your water is safe, clean, and not damaging to your home or the environment.
For more information on water quality standards, you can visit the U.S. Environmental Protection Agency's website for guidance on pH and other water quality criteria.
