Your water / Your source
Which plant serves your address?
of customers served by the Potomac plant
WSSC Water comes from two rivers: the Potomac plant serves about 75% of customers, the Patuxent serves the area around Laurel, and some areas get a blend, so check your address on the utility’s map.
By the Your Water Numbers desk, not WSSC Water · Updated · How we check
Look up your area: likely source, then check the map
| Area | Likely source | Hardness avg | Note |
|---|---|---|---|
| Most of Montgomery | Potomac | 154 mg/L | The utility’s description |
| Large part of lower Prince George’s | Potomac | 154 mg/L | The utility’s description |
| Around Laurel, Prince George’s | Patuxent | 70 mg/L | The utility’s description |
| Middle Prince George’s | Blend | No figure | The utility’s description |
| Small southern part of Montgomery | Blend | No figure | The utility’s description |
| Rockville | Potomac | Depends on plant | Likely; check the map |
| Gaithersburg | Potomac | Depends on plant | Likely; check the map |
| Bethesda | Potomac or blend | Depends on plant | Likely; check the map |
| Silver Spring | Potomac or blend | Depends on plant | Likely; check the map |
| Fort Washington | Potomac | Depends on plant | Likely; check the map |
| Oxon Hill | Potomac | Depends on plant | Likely; check the map |
| Laurel | Patuxent | Depends on plant | Likely; check the map |
| Bowie | Blend | Depends on plant | Likely; check the map |
| College Park | Blend or Patuxent | Depends on plant | Likely; check the map |
Source: The utility’s page on where water comes from · Town rows are our reading
Reading this: The five area rows follow the utility’s wording. The town rows are our reading of that wording and nothing more: none of them is a statement of fact about your street.
How do you find your actual plant?
Use the interactive map on WSSC Water’s general water page, which works by address. It answers this better than any table here, because a town name covers many streets.
The utility publishes a description by area and a map. We found no published list of towns by plant. That’s why every town above carries the same two words: likely, and check.
How big is each plant’s share?
About three in four customers are on the Potomac plant, by WSSC Water’s own count in its September 2026 request. The utility serves 1.9 million customers in all.
WSSC Water figure
Our arithmetic
Source: WSSC Water request, Sept. 2026 · Sept 2026
What happened when one plant had trouble?
Every customer was asked to cut back. A Potomac plant power fault on September 29–30, 2026 brought a systemwide essential-use request, meant to head off a boil-water advisory. It was lifted the next day.
The output figures show how much the two plants lean on each other. million gallons a day (MGD) means million gallons a day.
Source: WSSC Water request, Sept. 2026 · Sept 2026
So a notice can reach you whichever plant serves your home. See how boil-water and essential-use notices work.
Does your plant change what you should do?
It changes what you plan for, not your safety steps. The clearest difference is hardness: 154 mg/L on average for Potomac, 70 for Patuxent. The 2025 tap report gives both.
Your plant has no bearing on the lead steps. Those depend on the plumbing between the main and your glass. The PFAS figures do differ by plant, so look up yours.
What if you’re in a blend area?
Expect no single number. The figures we read cover the two plants, and no separate line appears for blended water. A home test tells you more than a guess from the map.
Do you need a test kit?
Most homes don’t. If the map gives you a plant and your fixtures look fine, the report figure is enough. A kit helps if you’re on a blend, or you’re choosing softener settings and want a reading from your own tap.
What to do with this number
- Put your address into the utility’s map
- Note the plant, then read its line in the tap report
- Keep the result with your bill papers
Questions on this page
Is Rockville on the Potomac plant?
Likely, because the utility says most of Montgomery County is. Only the address map can confirm it for your street.
Why isn’t there a firm list of towns?
We found a description by area and a map, not a town list. Assigning towns as fact would be guesswork.
Is the Patuxent plant bigger or smaller?
We have its 90–95 MGD output during the September 2026 outage, not a normal-day comparison. By customers, about 75% are on the Potomac plant.
Where each number comes from
| Figure | What it is | Source | As of |
|---|---|---|---|
| About 75% | Customers served by the Potomac plant | WSSC Water request, Sept. 2026 | Sept 2026 |
| 25% | Remainder of customers | Our arithmetic | Sept 2026 |
| 100–120, 90–95, 170 MGD | Plant output and average demand | Bethesda Magazine; WSSC Water request | Sept 2026 |
| 1.9 million | Customers served | WSSC Water request, Sept. 2026 | Sept 2026 |
| Sept 29–30 | Request and lifting | Bethesda Magazine | Sept 2026 |
| 154 and 70 mg/L | Plant hardness | WSSC Water 2025 tap report | Latest report |
| Source by area | Description and map | The utility’s page on where water comes from | Page as read |