Common Causes of Low Water Pressure (And How to Fix Them)
A weak trickle from your shower or faucet is more than an annoyance — it can signal a serious plumbing issue. Low water pressure has a handful of well-known culprits, and many of them you can diagnose yourself before calling a plumber. Here's a comprehensive breakdown of every common cause and what to do about it.
First: Is It Just Your Home or the Whole Street?
Before diagnosing your plumbing, check with neighbors. If multiple homes on your street have low pressure, the problem is with the municipal supply — not your pipes. Call your water utility and report it. They're responsible for everything up to your meter.
If it's just your home, continue reading. The problem is somewhere between the street and your fixtures.
The Most Common Causes of Low Water Pressure
1. Clogged Faucet Aerator or Showerhead
If pressure is low at just one fixture, a clogged aerator or showerhead is almost always the culprit. Mineral deposits (especially calcium in hard-water areas) build up in the tiny mesh screen at the end of your faucet. Unscrew the aerator, rinse it, or soak it in white vinegar overnight. For showerheads, submerge the head in a bag of vinegar for a few hours. This fix is free and takes 10 minutes.
2. Partially Closed Shutoff Valves
Every home has two main shutoff valves — one at the meter and one where the water line enters the house. If either was recently turned and not fully reopened, you'll get reduced pressure everywhere. Check that both valves are fully open (turned all the way counterclockwise for gate valves, or lever parallel to the pipe for ball valves). This is a frequent cause after plumbing repairs.
3. Failing Pressure Regulator Valve (PRV)
Most homes have a bell-shaped pressure regulator valve where the main supply enters. It's preset to keep household pressure between 45–80 PSI. When the PRV fails, pressure can drop dramatically or become erratic. A plumber can test your pressure with a gauge and replace the PRV if needed. Replacement costs $200–$400 in parts and labor.
4. Corroded or Old Galvanized Pipes
Homes built before 1970 often have galvanized steel pipes. Over decades, rust and mineral buildup coat the interior walls, narrowing the pipe's diameter. This is a progressive problem — pressure gets worse each year. The only permanent fix is repiping with copper or PEX. It's a significant investment ($3,000–$15,000 depending on home size) but eliminates the problem permanently.
5. Hidden Water Leak
A significant leak somewhere in your system diverts water before it reaches your fixtures, dropping pressure throughout the house. Signs of a hidden leak include: water stains on ceilings or walls, soft spots in flooring, unexplained increases in your water bill, and the sound of running water when all fixtures are off. If you suspect a leak, shut off all water use and watch your water meter — if it keeps moving, you have a leak.
6. Water Demand Peaks
If pressure is only low in the morning (when neighbors shower) or in the evening (when dishwashers run), you're experiencing municipal demand peaks. Your pressure regulator is working fine — everyone's simply drawing from the same supply simultaneously. Adjusting your schedule slightly often resolves the frustration without any repairs.
7. Clogged or Corroded Water Softener
Water softeners have a resin bed that filters minerals. When the resin becomes exhausted or the unit malfunctions, it can restrict flow significantly. Bypass the softener temporarily to see if pressure improves. If it does, the softener needs servicing or replacement.
8. Water Heater Issues
If low pressure is only at hot water fixtures, your water heater may be the culprit. Sediment buildup in older tanks, a partially closed inlet valve, or a failing hot side shutoff can all restrict hot water flow. Flush your water heater annually to prevent sediment buildup.
How to Measure Your Water Pressure
A pressure gauge costs about $10 at any hardware store. Thread it onto an outdoor hose bib, turn on the water fully, and read the gauge. Normal residential pressure is 45–80 PSI. Below 40 PSI is considered low. Above 80 PSI is high pressure (which damages pipes and fixtures over time).
When to Call a Plumber
Call a licensed plumber when:
- Pressure is low throughout the entire house (not just one fixture)
- You've checked all shutoff valves and the PRV looks fine
- You suspect a hidden leak — a plumber can use leak detection equipment
- Your home has old galvanized pipes and pressure has been declining for years
- The PRV needs replacement (requires cutting the line)
- Water meter shows movement with all fixtures off
Find a Plumber for Low Water Pressure
If DIY fixes haven't solved the problem, a licensed plumber can diagnose it properly. National Plumber Connect matches you with verified pros in your area.
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