Water & Pipe Emergency
Low Water Pressure Throughout Your House? Here's Why.
A sudden pressure drop is usually a sign of something specific — not just 'getting old.' This guide walks through the most likely causes and how to track down the problem.
What's Going On
Understanding the Problem
Water pressure problems fall into two categories: sudden pressure loss (something changed recently) and gradual pressure decline (something has been building for a while). Sudden loss usually points to an active leak, a failed pressure-reducing valve, or a municipal supply issue. Gradual decline usually points to mineral buildup, corroding pipes, or a slowly failing component. Knowing which type you're dealing with — and whether the low pressure is throughout the whole house or isolated to one fixture — is the key to diagnosing the problem correctly.
Diagnosis
Common Causes
1Failing or incorrectly set pressure-reducing valve (PRV)
Most Houston homes have a pressure-reducing valve where the main water line enters the house — usually a brass bell-shaped fitting near the main shutoff. The PRV reduces municipal water pressure (which can be 80–150 PSI) down to a safe residential range of 40–80 PSI. PRVs typically last 10–15 years. When they fail, they can fail in either direction: the valve can stick open (allowing dangerously high pressure) or stick partially closed (reducing pressure to a trickle). A failing PRV is one of the most common causes of whole-house pressure problems.
2Mineral buildup in older galvanized steel pipes
Homes built before approximately 1980 often have galvanized steel supply pipes. These pipes rust from the inside out, and the rust and mineral deposits gradually narrow the interior diameter of the pipe — sometimes down to the size of a pencil in severe cases. The pressure drop is gradual and the homeowner often doesn't notice until the pipes are almost completely occluded. At this point, the only real fix is repiping with copper or PEX.
3Active leak somewhere in the supply system
A burst or leaking pipe — inside the wall, in the attic, or underground in the yard — can cause a sudden and significant drop in water pressure throughout the house as water escapes the system. Check for wet spots in the yard, water stains on walls or ceilings, or a water meter that continues to move after all fixtures are shut off. Any of these indicates an active leak.
4Municipal supply interruption or area maintenance
Houston Public Works regularly performs maintenance on the water distribution system, which can cause temporary pressure drops in a neighborhood. If your neighbors are also experiencing low pressure at the same time, this is almost certainly the cause. Check the City of Houston water outage map or call 311 for information on planned work in your area.
5Clogged aerators or showerheads
If low pressure is isolated to one or two fixtures rather than throughout the house, the problem is almost certainly a clogged aerator or showerhead — not the plumbing system itself. Houston's hard water deposits calcium and mineral scale inside fixture aerators and showerhead holes, gradually blocking flow. These are easy to clean or replace and are not a plumbing system problem.
6Partially closed shutoff valve
If pressure dropped suddenly after any plumbing work, check whether the main shutoff valve or a branch shutoff was left partially closed. A ball valve needs to be turned fully parallel to the pipe to be fully open; a gate valve needs to be turned all the way counterclockwise. A valve even 10–20% closed can significantly restrict flow.
DIY Troubleshooting
What You Can Try
Determine whether the problem is whole-house or isolated
Check pressure at multiple fixtures throughout the house — kitchen, bathrooms, hose bibs outside. If pressure is uniformly low everywhere, the problem is in the supply system (PRV, main valve, municipal supply, or underground leak). If pressure is low at only one fixture, check the aerator or fixture shutoff valve at that location.
Clean a clogged aerator or showerhead
Unscrew the aerator from the faucet tip (it threads off counterclockwise — you may need pliers wrapped in tape to avoid scratching the finish). Soak it in white vinegar for 30–60 minutes, scrub with a small brush, then rinse thoroughly. For showerheads, fill a plastic bag with vinegar, tie it around the showerhead so the holes are submerged, and leave it for several hours. This removes calcium deposits and often restores full flow.
Check that all shutoff valves are fully open
Locate the main shutoff valve (near the water meter or where the main line enters the house) and any secondary shutoffs under sinks or at fixtures. Make sure each one is fully open. For ball valves, the handle should be parallel to the pipe. For older gate valves, turn counterclockwise until it stops.
Check your water meter for continuous movement
Shut off all water in the house and look at your water meter. Most meters have a small triangular 'flow indicator' that moves when any water is passing through. If that indicator is moving when everything is off, you have an active leak somewhere in the system, which may be causing the pressure drop.
Ask your neighbors if they're experiencing the same thing
A quick conversation or text to a neighbor can instantly tell you whether this is a municipal issue or a problem with your specific house. If it's city-wide in your block, the fix is just waiting. If it's only your home, the cause is on your property.
Know When to Call
When to Call a Pro
Call ARG Plumbing at (832) 419-3411 if whole-house pressure is consistently low and cleaning aerators didn't help, if you suspect a failing PRV (we can test your actual pressure and the PRV's performance in minutes), or if you have galvanized pipes in a home built before 1980 — at that point a camera inspection and repiping consultation may be more cost-effective than chasing individual pressure problems.
Pro Tip
Buy a water pressure gauge — they're about $10 at any hardware store and thread onto a hose bib. Normal pressure should read between 45 and 75 PSI. Anything below 40 PSI explains why your shower feels weak. Anything above 80 PSI is damaging your appliances, supply lines, and pipe joints over time. Knowing your actual pressure takes the guesswork out of diagnosing pressure problems and is useful information to have before you call a plumber.
Hristo
Master Plumber · ARG Plumbing