Quick Answer: Denver water is approximately 8.5 grains per gallon (gpg) — classified as hard. The main concerns are PFAS contamination from firefighting foam and uranium from Colorado's mining legacy. The best solution for Denver homes is a whole-home water softener combined with a carbon filter for PFAS removal, plus a reverse osmosis system for drinking water.
How Hard Is Denver Water?
Denver Water Hardness Data
According to Denver Water data, water hardness averages 8.5 gpg but can range from 7-16.4 gpg depending on the source and season. During dry winters, mineral concentrations increase as water levels in reservoirs drop, making water harder.
Where Does Denver Get Its Water?
Denver draws its water from the South Platte River and snowmelt from the Rocky Mountains, collected in reservoirs like Dillon Reservoir, Cheesman Reservoir, and Strontia Springs Reservoir. The water travels through mineral-rich geology that adds calcium and magnesium before treatment by Denver Water.
What Contaminants Are in Denver Water?
According to Denver Water Quality Reports and EPA data, Denver water contains several contaminants of concern:
Contaminants of Concern
- PFAS (Forever Chemicals): From firefighting foam used at airports and military bases in the South Platte River watershed.
- Disinfection Byproducts (TTHMs, HAA5): Formed when chlorine reacts with organic matter in water.
- Uranium: Naturally occurring from Colorado's mining legacy and geology.
- Nitrates: From agricultural runoff in the South Platte River basin.
- Chromium-6: The carcinogenic form of chromium, detected in some areas.
What Are the Health Effects of Denver's Hard Water?
Beyond the chemical contaminants, Denver's hard water causes its own set of problems:
Skin and Hair Issues
Denver's 8.5 gpg water can disrupt the natural oil balance of skin and hair. Many residents report dry skin, eczema flare-ups, and frizzy hair that's difficult to manage. The mineral content can also make soap less effective, requiring more product for cleaning.
Appliance and Plumbing Damage
At 8.5 gpg, scale accumulates inside water heaters (reducing efficiency by 15-20%), dishwashers (leaving white film on dishes), washing machines, and coffee makers. Hot water pipes gradually narrow from scale buildup, reducing flow and eventually requiring replacement.
Economic Impact
The EPA estimates that hard water costs U.S. households $800–$1,500 per year in excess energy, detergent use, and appliance wear. In Denver, with its 8.5 gpg water, these costs are significant.
What Are the Best Water Treatment Solutions for Denver Homes?
Given Denver's hard water and PFAS contamination profile, a comprehensive approach is recommended:
1. Whole-Home Water Softener (Recommended)
A salt-based ion exchange water softener is recommended for Denver homes to address the 8.5 gpg hardness. Look for softeners rated for 10-15 gpg to handle Denver's hardness with capacity to spare.
2. Whole-Home Carbon Filtration
A whole-home carbon filter removes chlorine, chloramines, and disinfection byproducts before water enters your home's plumbing. This also helps remove PFAS compounds, which are a significant concern in Denver water.
3. Reverse Osmosis (Drinking Water)
For drinking and cooking water, a reverse osmosis (RO) system under the kitchen sink is essential for Denver homes. RO removes dissolved minerals to near-zero levels, plus filters out PFAS, uranium, nitrates, and disinfection byproducts.
Denver Water Hardness vs. Other Major Cities
| City | Hardness (gpg) | Classification |
|---|---|---|
| Las Vegas, NV | 16-18 | Extremely Hard |
| Phoenix, AZ | ~16 | Extremely Hard |
| Dallas, TX | ~14 | Very Hard |
| Denver, CO | ~8.5 | Hard |
| Chicago, IL | ~8.2 | Hard |
| Seattle, WA | ~1.2 | Soft |
DIY Hard Water Test for Denver Residents
You don't need to wait for a lab report to know if you have a hard water problem. Here's a simple home test:
- The soap test: Fill a clear water bottle halfway with tap water. Add about 10 drops of pure liquid soap (like castile soap) and shake vigorously for 10 seconds. If you get abundant, persistent suds — water is soft. If the water looks milky or cloudy with few suds — you have hard water.
- The visual test: Check the inside of your toilet tank, water heater drain valve, or showerhead for white, crusty buildup. This is limescale — a sure sign of hard water.
- The spot test: Let a few drops of water dry on a dark surface like a black countertop or mirror. If you see white mineral spots after evaporation, you have hard water.