Is Rockville, MD Tap Water Safe to Drink?
Yes, Rockville tap water is safe to drink. Hardness is low at 61 PPM, and no contaminants exceed health guidelines. Most homes here don't need treatment.
Hardness Scale: Where Rockville Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Rockville Compares
Rockville's water is 56% softer than the national average of 138 PPM - ranking in the bottom 66% for hardness nationwide. Most homes here do not need a softener. Within Maryland, it ranks #7 of 15 cities (9% below the state average of 67 PPM). Among cities (50k-100k), Rockville ranks #187 of 258 for hardness.
What Rockville's Water Means for Your Home
Hardness: 61 PPM - Low Concern
Rockville's water is moderately hard at 61 PPM. You'll see some spotting on glassware and a film on shower doors over time, but it's not the kind of hardness that demands a full softener. A salt-free conditioner is worth considering if you have a tankless water heater or high-end fixtures.
Contaminants & Safety
Disinfection byproducts are the notable finding here. Rockville's water has TTHMs at 41.5 ppb and HAA5 at 20.1 ppb — both within legal limits, but the EWG health guidelines are far stricter. These byproducts form when chlorine reacts with organic matter during treatment. A whole-house activated carbon filter reduces both chlorine and its byproducts. Want the full picture? Request your utility's annual Consumer Confidence Report.
What's in the Treatment Process
Rockville's surface water supply requires heavy chlorination to stay safe — but that creates a tradeoff. The treatment process generates disinfection byproducts: TTHMs at 41.5 ppb (52% of the legal limit, but 277x the EWG guideline) and HAA5 at 20.1 ppb (34% of the legal limit, but 201x the EWG guideline). These are within legal limits, but the EWG sets much tighter thresholds based on cancer-risk research. A whole-house activated carbon filter reduces both chlorine and byproducts.
Chromium-6 was detected at 0.0899 ppb, which is 4.5x the EWG health guideline. There's no separate federal limit for chromium-6, only total chromium. A reverse osmosis system is the most effective removal method. All measurements are within federal legal limits. The EWG guidelines represent a more conservative, health-based standard.
| Contaminant | Detected | Health Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Hardness (as CaCO₃) | 61 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 99 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | 19.92 ppt | — | No total limit | Detected |
| ↳ PFOA | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| ↳ PFOS | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| Lead | 3 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ✓ Low |
| Chlorine / Chloramine | 1.1 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 1.3 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Recommendations for Rockville Homes
Quick Fix for Chlorine: Shower Filter
At 1.1 mg/L chlorine, many Rockville residents notice dry skin, brittle hair, and that "pool smell" in the shower. A shower filter installs in 5 minutes, no tools needed.
How to Test Your Water in Rockville
City-wide data is a solid starting point, but your specific tap might differ based on plumbing age, distance from the treatment plant, or seasonal changes.
Free option: Request WSSC Water's annual Consumer Confidence Report for official city-level data.
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About Rockville's Water Supply
Water Utility: WSSC Water
Water Source: Potomac River (Surface Water)
Population Served: 52,000
Hardness: 61 PPM (3.6 grains per gallon)
Rockville's drinking water comes from surface sources — Potomac River. Surface water requires more extensive treatment than groundwater, including coagulation, filtration, and disinfection. This heavier chlorination is why disinfection byproducts tend to be higher in surface-supplied systems. On the upside, surface sources often deliver softer water than deep aquifers. The system serves 52,000 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request WSSC Water's Consumer Confidence Report (CCR) or test your own tap.
ZIP Codes Covered by This Report
This water quality data applies to all areas served by WSSC Water in Rockville, MD, including ZIP codes:
20817, 20830, 20832, 20833, 20847, 20848, 20849, 20850, 20851, 20852, 20853, 20854, 20855, 20857, 20860, 20880
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Compare Rockville to Other Maryland Cities
Frequently Asked Questions About Rockville Water
Is Rockville tap water safe to drink?
Where does Rockville's water come from?
Do I need a water softener in Rockville?
What is the hardness of Rockville water in grains per gallon?
What are disinfection byproducts in Rockville's water?
Is chromium-6 in Rockville's water?
Why does Rockville water taste like chlorine?
Can I drink Rockville tap water straight from the faucet?
Data sources: Lead and copper data from EPA Safe Drinking Water Act LCR reporting. Contaminant data from utility-reported testing results. PFAS data from EPA UCMR5 (2023–2025). Hardness from USGS and municipal reports. Data reflects system-level testing results and may not match your specific tap due to neighborhood plumbing, season, or recent utility changes. For your utility's latest results, request their Consumer Confidence Report (CCR). Our methodology. Last updated: 2026-02-24.
What Rockville Homeowners Actually Buy
Common purchases for homes with 61 PPM water.
Affiliate disclosure: we may earn a commission. Selection based on Rockville's water data.