Why is my water pressure suddenly low in my Los Angeles home?

Sudden low water pressure in an LA home is most commonly caused by: a partially closed main shutoff valve, a failing pressure reducing valve (PRV), a hidden leak losing pressure from the system, or LADWP water main work in your area. Check the LADWP outage map, then inspect your shutoff valves before calling a plumber.

What is a pressure reducing valve (PRV) and how do I know if mine is failing?

A PRV (pressure reducing valve) is a bell-shaped device on your main supply line that reduces LA's street pressure (typically 80–150 PSI) to a safe household level (40–60 PSI). A failing PRV causes either very low pressure throughout the house or — when it fails open — dangerously high pressure that can burst pipes and damage appliances. PRVs typically last 10–15 years and cost $200–$500 to replace in LA.

Low Water Pressure in Los Angeles — Causes & How to Fix It

Q: How do I increase water pressure in my shower?

First, remove and soak the showerhead in white vinegar overnight to dissolve mineral scale. If pressure is still low only in that shower, check the shower valve cartridge for buildup. If low pressure affects multiple fixtures, the issue is in the supply line or PRV — call a plumber.

Q: What is normal water pressure for a house in Los Angeles?

Normal household water pressure is 40–80 PSI. Los Angeles street pressure from LADWP typically runs 80–150 PSI, which is why most homes have a pressure reducing valve (PRV) to bring it down to a safe range. Below 40 PSI feels weak; above 80 PSI can damage fixtures and water heaters over time.

A weak shower or trickle from the faucet is frustrating — and in LA, it usually has one of eight specific causes. Here's how to diagnose and fix each one.

Quick Answer: If the low pressure is in one fixture → clogged aerator or cartridge. If it's throughout the whole house → check that your main shutoff valve is fully open, then suspect the pressure reducing valve (PRV) or a hidden leak. Start by checking the LADWP alerts page for active main work in your area.

Is the Pressure Low Everywhere, or Just One Place?

This single question determines everything:

One fixture or area → localized issue (clogged aerator, cartridge, supply line). Usually a DIY fix under $20.
Whole house → main shutoff, PRV, hidden leak, or LADWP supply issue. May need a plumber.
Hot water only → failing water heater, partially closed isolation valve at the heater, or scale buildup in the heater's cold inlet filter.

8 Causes of Low Water Pressure in LA Homes

1. Clogged Aerator or Showerhead (DIY — $0–$5)

LA's mineral-rich water deposits calcium and magnesium scale on faucet aerators and showerheads over time. Unscrew the aerator (counterclockwise), soak it in white vinegar for 30 minutes, scrub with an old toothbrush, and reinstall. Do the same with the showerhead — soak it in a bag of vinegar tied around it overnight. This fixes most single-fixture pressure issues.

2. Partially Closed Shutoff Valve (DIY — $0)

Your home has at least two main shutoff valves: one at the street (round wheel type, for LADWP) and one inside your home (usually a ball valve with a lever handle, often in the garage or near the water meter). If either is partially closed, whole-house pressure drops. Make sure the lever is parallel to the pipe (open) not perpendicular (closed).

3. Failing Pressure Reducing Valve / PRV ($200–$500)

Most LA homes have a PRV (a bell-shaped brass fitting on your main supply line, often near the meter or garage). It reduces LADWP's high street pressure (80–150 PSI) to a safe household range (40–60 PSI). PRVs last 10–15 years; a failing PRV can cause whole-house low pressure. A plumber can test your pressure with a gauge — a $200–$500 PRV replacement is a straightforward job.

4. Hidden Leak in the Supply Line (Call a Plumber)

A leak is bleeding pressure from your system. If your water meter test shows movement with everything off (see our hidden leak guide), a leak is robbing pressure. Don't delay — a running leak is also running up your LADWP bill.

5. LADWP Main Work in Your Area (Wait it Out)

Pressure drops during active water main work are common in LA. Check ladwp.com for active alerts or call LADWP at (800) 342-5397 before spending money on a plumber.

6. Corroded Galvanized Supply Pipes (Repipe: $4,000–$15,000)

Homes built before 1970 in LA commonly have galvanized steel supply pipes. Galvanized pipes corrode from the inside out, accumulating rust and mineral deposits that dramatically reduce the effective pipe diameter over decades. If your home is older and pressure has slowly decreased over years — not suddenly — corroded pipes are likely the cause. The fix is repiping with copper or PEX. Get quotes from at least three licensed C-36 plumbers.

7. Faulty Shower Valve Cartridge (DIY or Plumber: $50–$200)

If the pressure is weak only in one shower, the internal cartridge of the shower valve may be corroded or scaled. Replacement cartridges are $20–$50 for most major brands (Moen, Delta, Kohler). This is a moderate DIY job — you need to shut off the supply, remove the shower handle and trim, and swap the cartridge.

8. Water Heater Scale (DIY or Plumber: $0–$300)

Hot water pressure only? Scale buildup in the cold water inlet filter screen of your water heater, or a partially closed isolation valve, can restrict hot-side pressure. Check the isolation valve on the cold supply line to the heater (should be fully open). Flush the heater to remove sediment — ideally done annually in LA's hard water environment.

How to Measure Your Water Pressure

A pressure gauge ($10–$15 at any hardware store) threads onto a hose bib (outdoor spigot). Turn on the tap and read the gauge. Normal is 40–80 PSI. Under 40 PSI explains your pressure complaints; over 80 PSI is damaging your pipes and appliances even if it "feels good."

Frequently Asked Questions

Why is my water pressure suddenly low in my LA home?

Sudden whole-house low pressure: check for a partially closed shutoff valve, LADWP main work nearby, or a failing PRV. Sudden low pressure in one fixture: clean the aerator or showerhead first.

What is a pressure reducing valve (PRV)?

A PRV is a bell-shaped brass device on your main supply line that reduces LADWP's high street pressure (80–150 PSI) to a safe household level (40–60 PSI). PRVs last 10–15 years and cost $200–$500 to replace when they fail.

How do I increase water pressure in my shower?

Remove the showerhead and soak it in white vinegar overnight to dissolve mineral scale. If still low in only that shower, the cartridge may need replacement ($50–$200). If low pressure affects the whole house, check shutoff valves and the PRV.

What is normal water pressure for a house in Los Angeles?

Normal household water pressure is 40–80 PSI. LA street pressure from LADWP typically runs 80–150 PSI, which is why most homes have a PRV. Below 40 PSI feels weak; above 80 PSI can damage fixtures and water heaters over time.

Hiring a plumber?

Plumbsie doesn't send plumbers or refer jobs. Before you hire anyone, look up their license at cslb.ca.gov (California plumbers hold a C-36 license), confirm it's active, and get written estimates from more than one licensed plumber.

How to vet a plumber