First Question: One Fixture or the Whole House?
This single distinction determines almost everything about how urgently to treat a pressure drop and what's likely causing it.
If It's Just One Faucet or Fixture
This usually means a clogged aerator (the small screen at the tip of a faucet catching mineral deposits over time), a partially closed shutoff valve under that specific sink, or mineral buildup restricting flow inside that fixture's cartridge. None of these are emergencies, and all are relatively simple, affordable fixes.
If It's the Whole House, Suddenly
This points to something upstream affecting the entire system — a main valve that's been partially closed (sometimes accidentally, during other work in the house), a pressure-reducing valve failure, or, more seriously, a leak somewhere in the supply line between the meter and the house.
Checking for a Leak: The Meter Test
This is the single most useful diagnostic step you can do yourself before calling anyone, and it takes just a few minutes.
How to Run the Test
Make sure every fixture and water-using appliance in the house is off — including things people forget, like an ice maker or an irrigation system on a timer. Locate your water meter (often near the curb in an underground pit, or in a basement utility area) and note the current reading, or simply watch whether the dial or digital display is moving. If the meter is still moving with everything off, water is flowing somewhere in your system even though nothing should be using it — a strong indication of a leak.
What This Tells You
A moving meter with everything off, combined with sudden pressure loss, strongly suggests the pressure drop is leak-related rather than a simple mechanical issue like a stuck valve — this shifts the situation from 'schedule a routine visit' to 'worth calling about promptly.'
Checking the Simple Causes First
Main Valve Position
If any plumbing work has recently happened in the house — even unrelated work, like an appliance installation — it's worth confirming the main shut-off valve is fully open, since it's occasionally left partially closed by mistake.
Pressure-Reducing Valve (PRV)
Many homes, particularly those on municipal systems with higher incoming pressure, have a PRV that regulates pressure down to a safe range for household plumbing. A failing PRV can cause a sudden, unexplained pressure change in either direction — a plumber can test this directly.
Municipal-Side Work
Nearby Arlington County water main work, whether planned maintenance or an emergency repair, can temporarily affect pressure for an entire area — a quick check of county utility announcements, or a call to Arlington's water utility, can confirm whether this explains a neighborhood-wide pressure change rather than an issue specific to your home.
When It's Likely a Leak Underground
If the meter test confirms water movement with everything off, and simple causes like the main valve and PRV check out normally, the leak is most likely somewhere in the supply line between the meter and the house — potentially underground, which is harder to diagnose without specialized equipment.
What a Plumber Checks Next
Acoustic leak detection equipment can pinpoint an underground leak's approximate location without exploratory digging across your entire yard, narrowing the repair to a targeted area rather than a broad excavation.
Why This Matters Beyond Just Comfort
Beyond the inconvenience of weak showers, an underground supply line leak wastes a meaningful amount of water continuously, which shows up as a rising water bill even before you notice the pressure change — and left unaddressed, it can eventually erode soil around the leak, potentially affecting nearby hardscape or even foundation soil over time. A sudden pressure drop is worth investigating promptly, not because it's always an emergency, but because the underlying cause, if it is a leak, tends to get more expensive to fix the longer it continues.
Need a Plumber in Arlington?
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Frequently Asked Questions
What's normal residential water pressure?
Most homes run comfortably between 40-60 psi; above 80 psi stresses fixtures and water heaters over time, while below 40 psi starts to feel noticeably weak.
Can Arlington's municipal water work affect my pressure?
Yes — nearby county water main work can temporarily affect pressure across an area; checking utility announcements or calling the water authority can confirm if it's area-wide rather than specific to your home.
How do I test my home's actual water pressure?
A simple pressure gauge that screws onto an outdoor hose bib gives an accurate reading in seconds, and these are inexpensive and widely available at hardware stores.
Is a slow, gradual pressure decline over months the same concern as a sudden drop?
No — gradual decline over an extended period usually points to mineral buildup in aerators or pipes, a maintenance issue rather than the leak-related concern that comes with a sudden change.
Should I be worried if only my upstairs bathroom has low pressure?
This localized pattern usually points to a fixture-specific or branch-line issue rather than a whole-house problem — worth mentioning to a plumber but not typically urgent.
Can a failing pressure-reducing valve cause pressure to be too high instead of too low?
Yes — a PRV failure can cause pressure to spike as easily as it can cause it to drop, and unusually high pressure has its own risks for fixtures and water heaters worth addressing.