While Denver Water publishes annual averages (currently 7.8 GPG), the actual hardness at your tap can vary based on the specific distribution pipes, well water mixing, or seasonal changes. Before sizing a water softener, you need to test your own water.
Red Flag: The "Free Test" Sales Pitch
Many water treatment companies offer "free in-home water testing." Be aware that this is a sales tool. While they often use accurate liquid drop kits, the test is designed to visually shock you into a purchase. We highly recommend testing the water yourself first so you have an independent baseline before inviting salespeople into your home.
Method 1: Test Strips
The easiest and most accessible method. You dip a paper strip into a cup of tap water, wait a few seconds, and match the color change to a chart on the bottle.
- Cost: $10 - $20 for a pack of 50+.
- Accuracy: Moderate (±2 GPG). Good for identifying a general range (e.g., distinguishing between 5 GPG and 15 GPG) but not precise.
- Where to get: Home Depot, Lowe's, or Amazon (look for brands like Hach or Varify).
Method 2: Liquid Drop Test Kits
This is what professionals use in the field. You fill a vial with a precise amount of water, add a buffer powder, and then count how many drops of a titrant solution it takes to turn the water from red to blue.
- Cost: $20 - $50.
- Accuracy: High (±1 GPG). If it takes 8 drops to turn blue, your water is 8 GPG.
- Where to get: Look for the Hach 5-B Hardness Test Kit. Highly recommended for DIY sizing.
Method 3: Electronic TDS Meter
A digital pen you stick in a cup of water to read Total Dissolved Solids.
- Cost: $15 - $30.
- Accuracy: Low for hardness specifically. A TDS meter measures all conductive dissolved solids (salt, iron, etc.), not just calcium and magnesium. It's a great tool for checking if an RO system is working, but poor for sizing a water softener.
Method 4: Professional Lab Testing
You fill a sample bottle and mail it to a certified laboratory.
- Cost: $50 - $200+.
- Accuracy: Perfect. They will test for hardness, plus 30+ other parameters like lead, arsenic, iron, and VOCs.
- When to use: Recommended if you are on private well water (common in areas south/east of Aurora) or if you are considering an expensive Whole-House filtration system and want to know exactly what needs filtering.
Interpreting Your Results in Denver
0 - 3 GPG (Soft)
No softener needed. You likely live in Boulder or are already using softened water.
4 - 7 GPG (Moderate)
A softener is optional but beneficial. You might consider a salt-free conditioner if you just want to protect appliances.
8 - 14 GPG (Hard)
This is typical Denver water. A traditional salt-based water softener is highly recommended to protect your home's plumbing and appliances.