Local water facts · Virginia
Prince William County Service Authority (West) serves 136,409 people from Lake Manassas + Occoquan Reservoir. The numbers below are from the utility’s own published testing, compiled by the EWG Tap Water Database (June 2026). The water is legal. The question is how it compares to health guidelines, which sit well below the legal limits.
Each card shows how far a contaminant sits above its health guideline, the level scientists consider protective over a lifetime of drinking. A system can pass every legal test and still carry these levels.
24.1 ppb found · health guideline 0.06 ppb
Cancer-linked Read the research on Haloacetic acids (HAA9) →26.8 ppb found · health guideline 0.15 ppb · legal limit 80 ppb
Cancer-linked Read the research on Total trihalomethanes (TTHMs) →16 ppb found · health guideline 0.1 ppb · legal limit 60 ppb
Cancer-linked Read the research on Haloacetic acids (HAA5) →5.7 ppb found · health guideline 0.06 ppb
Cancer-linked Read the research on Bromodichloromethane →6.6 ppb found · health guideline 0.1 ppb
Cancer-linked Read the research on Trichloroacetic acid →18.9 ppb found · health guideline 0.4 ppb
Cancer-linked Read the research on Chloroform →8.86 ppb found · health guideline 0.2 ppb
Cancer-linked Read the research on Dichloroacetic acid →2.25 ppb found · health guideline 0.1 ppb
Cancer-linked Read the research on Dibromochloromethane →0.0725 ppb found · health guideline 0.02 ppb
Cancer-linked Read the research on Chromium (hexavalent) →Each bar starts at the health guideline and runs on a log scale. The faint ticks mark 10× and 100× over, and the dark notch is the legal limit where one exists.
Health-effect labels and guideline levels above come from the EWG Tap Water Database (June 2026), advisory benchmarks set by EWG’s researchers (methodology), not legal standards. The utility’s water meets federal legal limits.
Think per glass: at 402× the guideline, one glass of tap water carries what 402 glasses would hold at the health-guideline level. The top flag here is Haloacetic acids (HAA9). Not an emergency, but worth knowing, because the fix is specific and usually simpler than people expect.
Get your free water report for your own ZIP: every flag scored, and which fix covers which one.
New to these reports? How to read a water report in 2 minutes.
Every system we track, plotted by Water Score, 0 to 100, higher is safer.
Prince William County Service Authority (West) scores 23/100, ranking #17 of 58 tracked systems.
No single filter does everything. Each option covers different flags, so the right answer depends on what’s in your water and how your house is set up. You’re weighing options, not grades of good.
Good on chlorine taste and some disinfection byproducts. Cartridges fade fast, about every 2 months.
The drinking-water workhorse: handles PFAS, nitrate, arsenic and most of the hard flags, at one tap. How Reverse Osmosis (RO) installation works →
Treats every tap and protects pipes and appliances, usually paired with Reverse Osmosis (RO) for the kitchen. What a softener fixes (and can’t) →
The full breakdown of what each option does and can’t do: the 60-second version · all the free guides.
Hardness isn’t in the EWG numbers above, but it’s the one you feel at home. Most Northern Virginia water runs hard, and the minerals settle out as sediment in a tank water heater and as scale in a tankless one. That’s what makes a heater rumble, run out of hot water sooner, and wear out early. A yearly flush clears it, and it’s the first step. Here’s how often to flush a water heater, and what it costs, and how hard each utility’s water runs.
Type your ZIP and get the full picture, free: every flag, what it means per glass, and which fix covers it. Then start with the water heater: a $99 flush (normally $199) with a plumbing safety check included. Tankless descaling is $300, regularly $350. You pay after the visit.
Get your free water report Book a $99 water heater flushThey probably haven’t seen these numbers. Send them this page. It takes 10 seconds, and they get their own free report.
📄 Get the printable one-page report (PDF)
Grab the postable Water Score card →