Why Is My Water Pressure Low? 8 Causes and Fixes

You turn on the shower and get a weak trickle. The kitchen faucet barely fills a pot. Low water pressure is one of the most frustrating plumbing problems homeowners face, and it can have many different causes.

This guide walks through the most common reasons your water pressure is low and what you can do about each one — from quick DIY fixes to issues that need a licensed plumber in Los Angeles.

Check If It's a Local or Whole-House Problem

Before troubleshooting, figure out where the low pressure is happening:

• One fixture only: The problem is likely at that fixture (clogged aerator, shut-off valve partially closed, or a kinked supply line).
• Hot water only: Your water heater is likely the issue (sediment buildup, failing valve, or undersized unit).
• Whole house: The problem is in your main supply, pressure regulator, or the municipal water system.

Common Causes of Low Water Pressure

1. Clogged Faucet Aerators

The aerator is the small screen screwed onto the tip of your faucet. Mineral deposits and debris clog it over time, restricting flow. This is the most common cause of low pressure at a single fixture.

Fix: Unscrew the aerator by hand or with pliers (wrap it in a cloth to avoid scratching). Soak it in white vinegar for 30 minutes, scrub with a toothbrush, and rinse. Replace it if it's badly corroded ($2–$5 at any hardware store).

2. Partially Closed Shut-Off Valve

Every fixture has a local shut-off valve, and your home has a main shut-off. If any of these were bumped or not fully reopened after a repair, you'll get reduced pressure.

Fix: Check the valve under the affected fixture (or the main valve near your water meter). Turn it fully counterclockwise (for gate valves) or parallel to the pipe (for ball valves). This is a surprisingly common cause that costs nothing to fix.

3. Failing Pressure Regulator

Most homes have a pressure regulator (also called a pressure-reducing valve or PRV) on the main water line where it enters the house. These are pre-set to keep pressure between 45–60 PSI. When they fail, pressure can drop dramatically across the whole house.

Fix: A plumber can test your pressure with a gauge ($10 at hardware stores if you want to DIY the test). If the PRV has failed, replacement costs $250–$500 installed. They typically last 10–15 years.

4. Corroded or Clogged Pipes

Older homes with galvanized steel pipes are especially prone to this. Over decades, mineral deposits build up inside the pipes, narrowing the diameter and restricting flow. This gets progressively worse and doesn't have a quick fix.

Fix: A plumber can inspect with a camera and recommend options. If corrosion is widespread, a whole-house repipe (to copper or PEX) is the long-term solution. In Los Angeles, repiping typically costs $5,000–$15,000 depending on house size and pipe material.

5. Water Heater Issues (Hot Water Only)

If the low pressure only affects hot water, sediment has likely built up in your water heater tank. Sediment settles at the bottom over time and can partially block the outlet.

Fix: Drain and flush the water heater (a DIY-friendly maintenance task you should do annually). If the unit is old (10+ years) and flushing doesn't help, replacement may be necessary. Consider a tankless water heater for consistent pressure and endless hot water.

6. Leaking Pipes

A hidden leak diverts water before it reaches your fixtures, reducing pressure. Signs include unexplained increases in your water bill, damp spots on walls or ceilings, or the sound of running water when nothing is on.

Fix: Check your water meter with all fixtures off. If the meter is still moving, you have a leak. Call a plumber for leak detection. In LA, leak detection costs $150–$400, and repair costs vary widely depending on location.

7. Municipal Water Supply Issues

Sometimes the problem isn't in your home at all. Main breaks, high-demand periods (summer mornings), or construction work on water mains can temporarily reduce pressure in your neighborhood.

Fix: Check with your neighbors — if they're experiencing the same issue, contact LADWP (Los Angeles Department of Water and Power) to report the problem and get an estimated resolution time.

8. Too Many Fixtures Running at Once

If pressure drops only when multiple fixtures are in use simultaneously (running the dishwasher while someone showers), your supply line may be undersized for your home's demand.

Fix: Stagger water usage as a short-term solution. For a permanent fix, a plumber can assess whether upgrading your main supply line diameter would help. This is more common in older homes with 1/2" main lines.

How to Test Your Water Pressure

You can measure your water pressure yourself with a pressure gauge ($8–$12 at hardware stores):

1. Make sure all faucets and water-using appliances are off.
2. Screw the gauge onto an outdoor hose bib (spigot).
3. Turn the spigot fully on and read the gauge.

Normal residential water pressure is 40–60 PSI. Below 40 PSI is considered low. Above 80 PSI is too high and can damage fixtures and pipes.

When to Call a Plumber

Call a professional if:

• Pressure is low throughout the entire house and cleaning aerators didn't help
• You suspect a hidden leak (meter running with all fixtures off)
• Your home has galvanized steel pipes and pressure has been declining gradually
• You need a pressure regulator tested or replaced
• Pressure dropped suddenly with no obvious cause

A diagnostic visit from a plumber typically costs $100–$250 in Los Angeles. Browse our directory of verified LA plumbers to compare ratings and find one near you.

Frequently Asked Questions

What is normal water pressure for a house?

Normal residential water pressure is 40–60 PSI. Most homes are set to around 50 PSI. Below 40 PSI is noticeably low, and above 80 PSI can damage pipes and appliances.

Can low water pressure damage my appliances?

Yes. Dishwashers and washing machines need a minimum pressure (usually 20 PSI) to operate correctly. Below that, they may not fill properly, run longer cycles, or fail to clean effectively.

Why is my water pressure low in the morning?

Morning is peak water usage time in most neighborhoods. Municipal supply may temporarily drop as many homes draw water simultaneously. If this happens regularly, a pressure booster pump ($300–$800 installed) can help maintain consistent pressure.

How much does it cost to fix low water pressure?

It depends on the cause. Cleaning an aerator is free. Replacing a pressure regulator costs $250–$500. A whole-house repipe can run $5,000–$15,000. Start with the cheap fixes before assuming you need major work.