Only one faucet is weak
A single sink has poor flow while nearby fixtures seem normal.
Start here: Start with the faucet aerator and the shutoff valves under that sink.
Plumbing
Low Water Pressure
Direct answer: Low water pressure is usually caused by a partly closed valve, a clogged faucet aerator or showerhead, a pressure problem affecting the whole house, or a hidden leak reducing flow.
Most likely: If the problem is only at one sink or shower, mineral buildup in the faucet aerator or showerhead is the most common cause. If every fixture is weak, start by checking the main shutoff and any pressure-reducing valve area before assuming a major failure.
The fastest way to diagnose low water pressure is to compare fixtures. A single weak faucet points to a local restriction. Several weak fixtures on one side of the home suggest a branch valve or branch piping issue. Weak pressure everywhere points to the main supply, a partially closed valve, a pressure regulator problem, a leak, or a utility-side issue.
Don’t start with: Do not start by buying a pressure-reducing valve, well parts, or replacing random fixture parts. First confirm whether the problem is at one fixture, one branch, or the whole house.
Only one faucet or shower is weak?Check the faucet aerator or showerhead first.
Every fixture is weak?Check the main shutoff position and look for signs of a leak or utility issue before touching parts.
Last reviewed: 2026-03-16
Start by matching the pressure-loss pattern
Only one shower is weak
The shower runs, but the spray is thin or uneven while sinks still seem normal.
Start here: Start with the showerhead for mineral buildup, then compare hot and cold flow.
Several fixtures are weak
More than one faucet or shower has low pressure, often in the same area or on the same floor.
Start here: Check whether a branch shutoff is partly closed and look for a hidden leak or recent plumbing work.
Whole house pressure is low
Cold and hot water both feel weak at nearly every fixture.
Start here: Check the main shutoff valve, ask neighbors if they have the same issue, and look for signs of a supply-side problem.
Most likely causes
1. Clogged faucet aerator or showerhead
This is the most common cause when only one fixture has weak flow, especially if pressure used to be normal and the drop happened gradually.
Quick check: Remove the faucet aerator or showerhead if accessible and see whether flow improves briefly with it off.
2. Partly closed shutoff valve
A valve under a sink, at a toilet branch, or at the main supply can reduce flow without shutting water off completely.
Quick check: Confirm the handle is fully open and compare the weak fixture to one fed by a different valve.
3. Hidden leak or supply restriction
If pressure is low at several fixtures or throughout the house, water may be escaping somewhere or the incoming supply may be restricted.
Quick check: Look for wet spots, sounds of running water when nothing is on, or a water meter that moves with all fixtures off.
4. Pressure regulator or well-system issue
Whole-house pressure loss that is steady and not tied to one fixture can come from the home's pressure control equipment.
Quick check: If you have a pressure-reducing valve or well system, note whether pressure is low everywhere and whether it changes suddenly or cycles oddly.
Step-by-step fix
Step 1: Figure out whether the problem is local, branch-wide, or whole-house
This separates simple fixture clogs from supply-side problems before you take anything apart.
- Test cold water at the kitchen sink, a bathroom sink, and one shower.
- Then test hot water at the same fixtures.
- Note whether the problem affects one fixture, one room or floor, only hot water, or the whole house.
- If you share municipal water, ask a nearby neighbor whether their pressure is also low.
Next move: You now know which branch to follow, which prevents unnecessary part buying. If the pattern is still unclear, continue with the visible checks and compare again after each step.
What to conclude: One weak fixture usually means a local restriction. Several weak fixtures suggest a branch issue or leak. Whole-house low pressure points to the main supply, a main valve, a regulator area, or a utility or well problem.
Stop if:
- You find active leaking, water staining, or pooling around walls, ceilings, or floors.
- Water pressure dropped suddenly and dramatically throughout the house without an obvious reason.
Step 2: Check the easiest restrictions first at the affected fixture
Mineral buildup and partly closed local valves are common, safe to inspect, and often fix the problem without replacement.
- If only one sink is weak, look under that sink and confirm both shutoff valves are fully open.
- If only one faucet is weak, unscrew the faucet aerator if accessible.
- Rinse debris from the faucet aerator and soak mineral buildup in plain vinegar if the part is metal and removable, then rinse well.
- If only one shower is weak, remove the showerhead if accessible and flush out debris or mineral buildup with water and a vinegar soak when appropriate.
- Briefly test flow with the aerator or showerhead removed, keeping water aimed safely into the sink or tub.
Next move: If flow improves with the aerator or showerhead cleaned or removed, the restriction was local. Reinstall the cleaned part or replace it only if it is damaged. If the fixture is still weak with the outlet fitting removed, the restriction is farther upstream. Move on to valve and branch checks.
What to conclude: Improved flow with the outlet fitting off confirms a clogged faucet aerator or showerhead. No change points to a valve, supply tube, cartridge passage, branch line, or broader pressure issue.
Step 3: Check shutoff valves and recent plumbing changes
Partly closed valves are easy to miss after repairs, winterizing, or work near the water meter or water heater.
- Check the main house shutoff and confirm it is fully open.
- If several fixtures in one area are weak, look for any branch shutoff serving that area and confirm it is fully open.
- Think back to any recent plumbing work, meter work, water heater service, or remodeling that may have left a valve partly closed.
- If only hot water is weak at multiple fixtures, compare cold flow to hot flow and note the difference for a plumber, since the restriction may be on the hot side rather than the general supply.
Next move: If pressure returns after opening a valve, monitor for leaks around that valve over the next day. If all visible valves are fully open and pressure is still low, check for evidence of a leak or supply-side problem.
Step 4: Look for signs of a hidden leak or supply-side issue
A leak can steal pressure and cause damage, and utility-side problems can mimic house-side failures.
- With all fixtures and appliances off, listen for running water in walls or near the meter area.
- Look for damp drywall, wet cabinets, soft flooring, or unexplained puddles.
- If your water meter is accessible, check whether it moves when no water is being used in the house.
- If you are on city water and neighbors also have low pressure, contact the water utility before assuming a house repair is needed.
- If the problem appeared during freezing weather, consider a partially frozen pipe branch and warm the space gradually rather than using open flame or high heat.
Next move: If you find a leak or confirm a utility issue, you have the likely cause and can stop further disassembly. If there is no sign of a leak and the utility is normal, the issue may be with pressure-control equipment or a less visible restriction.
Step 5: Decide whether this is still a DIY check or time to call a plumber
Beyond fixture cleaning and valve checks, diagnosis often involves pressure testing and system-specific components with higher fitment and damage risk.
- If only one faucet remains weak after cleaning the faucet aerator and confirming the shutoff valves are open, the faucet body or faucet cartridge passages may be restricted.
- If whole-house pressure is low and no leak or utility issue is found, note whether your home has a pressure-reducing valve or a well system and call a plumber or well technician for pressure testing.
- If pressure fluctuates, surges, or drops when another fixture runs, describe that pattern clearly when you call.
- If you confirmed a damaged faucet aerator during testing, replace it with the correct size and thread pattern for that faucet.
Repair guide: How to Replace a Faucet Aerator
A good result: You avoid guessing at high-fitment or system-level parts and focus only on the branch that testing supports.
If not: If the cause is still uncertain after these checks, professional diagnosis is the safest next step.
What to conclude: A confirmed local outlet restriction is a reasonable DIY repair. Whole-house pressure problems usually need measurement and system-specific diagnosis rather than guess-and-buy parts.
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FAQ
Why is water pressure low in only one faucet?
The most common cause is a clogged faucet aerator. Debris or mineral scale collects at the outlet and reduces flow. A partly closed shutoff valve under that sink is another common cause.
Why is my whole house water pressure low all of a sudden?
A sudden whole-house drop can come from a partly closed main valve, a hidden leak, a utility-side problem, or a pressure-control issue. Start by asking neighbors, checking the main shutoff, and looking for signs of running water when nothing is on.
Can a water leak cause low water pressure?
Yes. A leak can divert water away from fixtures and reduce pressure, especially if the leak is significant. If your meter moves with all fixtures off or you hear water running in the house, treat that as a likely leak until proven otherwise.
Should I replace the pressure regulator if pressure is low everywhere?
Not as a first step. Whole-house low pressure can have several causes, and pressure-reducing valves have high fitment and diagnosis risk. Confirm there is no utility issue, no partly closed valve, and no hidden leak first, then have pressure tested if needed.
Can hard water cause low water pressure?
Yes. Hard water can slowly clog faucet aerators and showerheads, and over time it can also narrow passages inside fixtures. That is why single-fixture problems should start with simple cleaning before bigger repairs.