Where Low Pressure Starts: Finding the Real Problem
Low water pressure usually comes from one of three places: a problem at the meter or main shutoff, a clogged pipe or fixture inside your house, or an issue with your water supplier. Before you buy anything or call a plumber, you need to know which one you have, because the fix is completely different for each.
Start by checking whether the problem is everywhere in your house or just one faucet. Turn on the kitchen sink, then the bathroom sink, then the shower. If only one fixture is weak, the clog is in that fixture or the line feeding it—a $20 fix. If everything is weak, the problem is either in your main line or upstream at the meter.
Next, call your water supplier and ask if they are doing work in your area or if they have a record of low pressure on your street. If they confirm low pressure is on their side of the meter, they will fix it at no cost to you. If they say pressure is normal, the problem is in your house.
Key Takeaways
- Low pressure in one fixture usually means a clogged aerator or shutoff valve; unscrew the aerator, rinse it, and screw it back on.
- Low pressure everywhere in the house points to a clogged main line, a partially closed shutoff valve, or a problem at the meter—call your water supplier first to rule out their side.
- A pressure regulator that has failed will cause pressure to drop gradually over weeks or months; replacing it costs $200 to $400 and requires a plumber.
- Mineral buildup in old pipes reduces pressure over time and cannot be fixed without replacing the pipes; a plumber can scope the line to confirm this.
- If your main shutoff valve is partially closed, opening it fully can restore pressure when ready, but a stuck valve may need replacement.
Cleaning the Aerator: The First and Fastest Fix
The aerator is the small screen at the tip of your faucet. Sediment and mineral deposits collect there and block water flow. If only one faucet is weak, this is almost always the culprit.
Unscrew the aerator by hand or with a wrench if it is stuck. Rinse it under running water and use an old toothbrush to scrub away any white or brown buildup. If the screen is damaged, buy a replacement aerator at any hardware store for $3 to $8 and screw it back on. Turn the faucet on and check the pressure. In most cases, this solves the problem in five minutes.
If the aerator is clean but pressure is still low at that one faucet, the shutoff valve under the sink may be partially closed. Look under the sink and find the small valve where the water line enters. Turn the handle counterclockwise until it stops. If pressure improves, the valve was the problem. If it does not, the clog is deeper in the line and a plumber will need to clear it.
Checking and Opening the Main Shutoff Valve
Your main shutoff valve controls water flow into your entire house. If it is partially closed, every faucet and fixture will have weak pressure. The valve is usually located where the water line enters your house—in the basement, crawlspace, or outside near the meter.
Locate the valve and look at the handle. If it is a lever handle, it should point in the same direction as the pipe (parallel to the flow). If it points across the pipe (perpendicular), the valve is closed or partially closed. Turn the handle to align it with the pipe. If the handle is a round knob, turn it counterclockwise until it stops. Do this slowly—do not force it.
Turn on a faucet and check the pressure. If it improved, the valve was the problem. If the handle is stuck and will not turn, or if you hear a grinding sound, the valve is failing and needs replacement. This requires a plumber and costs $150 to $300, but it is a straightforward job.
Replacing a Failed Pressure Regulator
A pressure regulator is a bell-shaped device usually mounted on the main water line just after the meter. It keeps pressure from the street from spiking and damaging your pipes. When a regulator fails, pressure drops gradually over weeks or months.
If pressure has been declining slowly and the aerators are clean and the main shutoff is fully open, the regulator may have failed. You can test this with a pressure gauge, which costs $10 to $15 at a hardware store. Screw it onto an outdoor faucet and turn the faucet on. Normal household pressure is 40 to 60 pounds per square inch (psi). If your reading is below 40 psi and everything else checks out, the regulator is likely the cause.
Replacing a pressure regulator requires turning off the main water supply, unbolting the old regulator, and installing a new one. This is not a difficult job, but it involves working with the main line and most homeowners hire a plumber. The regulator itself costs $50 to $100, and labor runs $150 to $300.
Mineral Buildup in Old Pipes
In houses with galvanized steel pipes installed before the 1980s, mineral deposits accumulate inside the pipes over decades. This buildup narrows the pipe opening and reduces pressure throughout the house. The problem gets worse slowly over many years.
If your house is older than 40 years, pressure has been declining gradually, and you have ruled out the aerator, shutoff valve, and regulator, mineral buildup is likely. A plumber can use a camera scope to look inside the main line and confirm this. If the buildup is severe, the only permanent fix is replacing the pipes, which is expensive. Partial solutions include installing a whole-house filter designed to catch sediment, though this will not restore pressure to what it was when the pipes were new.
If you are considering replacing old galvanized pipes anyway for other reasons (rust, discoloration in water), upgrading to copper or PEX pipe will restore pressure as a side benefit.
Installing a Booster Pump for Persistent Low Pressure
If your water supplier confirms that street pressure is low in your area, or if you live on a hill where gravity reduces pressure, a booster pump can increase pressure throughout your house. A booster pump is a small electric pump installed on the main water line that adds pressure to incoming water.
Booster pumps cost $300 to $800 for the unit itself, plus $200 to $500 for installation. They require a dedicated electrical outlet and a small storage tank. A plumber can assess whether a booster pump makes sense for your situation and what size you need. This is a good option if the problem is truly on the supplier's side and you have ruled out every other cause.
Before installing a booster pump, confirm with your water supplier that boosting pressure will not cause problems on their end. Some suppliers have rules about this.
When to Call a Plumber
Call a plumber if the main shutoff valve is stuck or will not turn, if you suspect a clog deep in the main line, if a pressure gauge shows pressure below 40 psi and you have ruled out the obvious causes, or if you are considering a booster pump. A plumber can scope the line with a camera, test pressure at different points, and identify exactly where the problem is.
Get a quote before work begins. A service call to diagnose the problem usually costs $100 to $200. Repairs range from $150 for a shutoff valve replacement to $1,500 or more if pipes need to be replaced. If the problem is on the supplier's side, the plumber's diagnosis will give you proof to show your water company.
Frequently Asked Questions
Why is pressure low in my shower but normal everywhere else?
The showerhead aerator is almost certainly clogged. Unscrew it, soak it in white vinegar for 30 minutes to dissolve mineral deposits, scrub it with a toothbrush, and screw it back on. If that does not work, the shutoff valve under the sink may be partially closed—turn it counterclockwise until it stops.
Can I increase pressure by adjusting the pressure regulator myself?
A pressure regulator has an adjustment screw on top, but turning it without a pressure gauge can damage your pipes or fixtures. If you want to adjust it, buy a pressure gauge first, test the current pressure, and turn the screw only a quarter turn at a time while testing. Most people hire a plumber for this because it is straightforward to overshoot and cause leaks.
Is low water pressure a sign of a leak?
Not usually. A leak would show up as water pooling, wet spots, or higher water bills. Low pressure without those signs points to a clog or a regulator problem. If you suspect a leak, check your meter before and after turning off all water in the house—if the meter keeps moving, you have a leak.
How long does it take to fix low water pressure?
Cleaning an aerator takes five minutes. Opening a shutoff valve takes ten minutes. Replacing a pressure regulator or clearing a main line clog takes a plumber two to four hours. If pipes need to be replaced, the job can take several days.
Will a whole-house water filter increase pressure?
No. A filter removes sediment but adds resistance to water flow, which actually lowers pressure slightly. A filter is useful if you have sediment in your water, but it will not solve a pressure problem.