Where Low Water Pressure Usually Comes From

Low water pressure at one fixture or throughout your whole house usually traces back to one of a few common causes. The most frequent culprit is a clogged aerator — the small screen at the tip of your faucet that breaks water into a fine spray. Mineral buildup from hard water can block it in weeks. The second most common cause is a closed or partially closed shut-off valve, either under the sink you're using or the main valve where water enters your house. The third is a leak somewhere in your supply line, which means water is escaping before it reaches your tap.

Less often, the problem originates outside your home: your water main may be damaged, your municipal supply may be experiencing pressure loss, or your water meter may be faulty. If your whole neighborhood has low pressure, call your water utility — the problem is theirs. If only your house is affected, the issue is in your plumbing or your shut-off valves.

Key Takeaways

  • Start by checking whether low pressure affects one faucet or your whole house, because a single fixture usually means a clogged aerator or closed valve under that sink.
  • Clean or replace the aerator by unscrewing it from the faucet tip, soaking it in vinegar to dissolve mineral deposits, and rinsing it thoroughly before reinstalling.
  • If pressure is low everywhere, locate your main shut-off valve (usually near the water meter or where the line enters the house) and make sure it is fully open.
  • A leak in your supply line will show as wet spots in your yard, basement, or crawl space, and requires a plumber to locate and repair.
  • If you have checked aerators and valves and pressure is still low, a plumber can test your water meter and supply lines to find the real cause.

Cleaning or Replacing a Clogged Aerator

An aerator is the easiest fix to try first because it costs nothing and takes five minutes. Unscrew the aerator by hand from the tip of the faucet — it usually comes off counterclockwise. If it is stuck, wrap a cloth around it and use pliers, but turn gently so you do not crack the faucet.

Once it is off, hold it up to the light. You will see a fine mesh screen inside. If it looks discolored or clogged with white or tan sediment, that is mineral buildup. Soak the aerator in white vinegar for 30 minutes to an hour. Use an old toothbrush to scrub away any remaining deposits, then rinse it thoroughly under running water. Screw it back onto the faucet and test the pressure.

If the aerator is too corroded to clean or if cleaning does not restore pressure, buy a replacement aerator at any hardware store for a few dollars. Bring the old one with you so the staff can match the thread size. Screw the new one on and test again. If pressure returns to normal, you are done. If it does not, the problem is elsewhere in your plumbing.

Checking Your Shut-Off Valves

Every sink has a shut-off valve underneath it, usually two of them — one for hot water and one for cold. If pressure is low at only one faucet, check the valves under that sink. Look for a small oval or round handle on each pipe. Turn both handles counterclockwise until they stop. They should turn easily and feel like they seat firmly. If one is only partially open, that is your problem.

If both valves under the sink are fully open and pressure is still low at that fixture, the issue is not a valve. Move on to checking your main shut-off valve. This is usually located near your water meter, in a basement, crawl space, or outside in a box in the ground. The valve handle should be parallel to the pipe (pointing in the same direction the water flows). If it is perpendicular to the pipe, it is closed. Turn it parallel to the pipe to open it fully.

After opening any valve, wait a few seconds for pressure to build, then test your faucet. If pressure improves, you have found the problem. If the main valve is already open and pressure is still low everywhere in the house, the problem is not a shut-off valve.

Looking for Leaks in Your Supply Line

A leak in your water supply line will reduce pressure throughout your house because water is escaping before it reaches your fixtures. Look for wet spots in your basement, crawl space, or yard. Check under sinks and around the water heater. If you see water pooling or damp soil in your yard, especially in a line from the street to your house, that is a strong sign of a leak in your main supply line.

A small leak may not be obvious. If you suspect one but cannot see it, turn off all water-using appliances and fixtures, then watch your water meter. If the meter is still moving, water is leaking somewhere. Write down the meter reading, wait an hour without using water, and check it again. If it has changed, you have a leak.

Leaks in supply lines require a plumber to locate and repair. Do not try to patch a supply line yourself — the repair will not hold under pressure. Call a plumber and describe where you see wet spots or where the meter is moving. They can use listening equipment or pressure tests to find the leak and fix it.

When to Call a Plumber

If you have cleaned the aerator, checked both shut-off valves, and found no obvious leak, but pressure is still low, a plumber can diagnose the real cause. They have tools to test your water meter, measure pressure at different points in your line, and identify blockages or damage you cannot see.

Call a plumber right away if you see water pooling in your yard or basement, because a leak will only get worse and will waste water and money. Also call if you turned on your main shut-off valve and pressure did not improve — the valve itself may be faulty and need replacement.

A plumber visit usually costs between $100 and $200 for a diagnostic call, depending on your area and how long the inspection takes. If they find a straightforward fix like a faulty meter or a clogged line, the repair may cost more, but you will know exactly what the problem is and how to prevent it in the future.

Preventing Low Pressure in the Future

Hard water causes mineral buildup in aerators and pipes over time. If you live in an area with hard water, clean your aerators every six months to a year. This takes five minutes and costs nothing. If buildup is severe, consider installing a whole-house water softener, which removes minerals before they enter your plumbing. A softener costs $500 to $2,500 installed, depending on the size of your house and the system you choose.

Check your shut-off valves once a year by turning them on and off gently. If a valve is hard to turn or does not move smoothly, it may be corroding inside and will eventually fail. Have a plumber replace it before it gets stuck.

Avoid letting your main shut-off valve sit in one position for years. Turn it on and off once or twice a year to keep it from seizing. If you ever need to use it in an emergency, you want to know it will move.

Frequently Asked Questions

Why is my water pressure low only in the morning?

Morning pressure loss often happens because water has been sitting in your pipes overnight and minerals have settled. Run the cold water for 30 seconds to a minute and the pressure usually returns to normal. If it does not, the problem is not mineral settling — check your aerator and shut-off valves.

Can I increase water pressure by adjusting something myself?

You can open a closed shut-off valve or clean an aerator, but you cannot safely increase the pressure your water company sends to your house. If pressure from the utility is low, only they can fix it. If your home pressure is low but the utility pressure is normal, the problem is in your plumbing or a valve, not something you can adjust.

What does it mean if pressure is high in some rooms and low in others?

Uneven pressure usually means a shut-off valve under one sink is partially closed, or an aerator in one fixture is clogged. Check the valves and aerators in the rooms with low pressure first. If those are fine, you may have a leak or blockage in the supply line to that part of the house.

Is low water pressure a sign of a serious problem?

Low pressure at one faucet is almost never serious — usually just a clogged aerator. Low pressure throughout your house could mean a leak, a faulty meter, or a problem with the municipal supply. A plumber can tell you which in about an hour.

Should I replace my water meter if pressure is low?

Only if a plumber has tested it and confirmed it is faulty. A faulty meter can restrict flow and lower pressure. Your water company may replace it for free if it is their equipment, or you may need to pay for a replacement if your meter is on your property. Ask your water utility whether they test meters and who pays for replacement.