Key Takeaways
- Low water pressure is typically caused by a plumbing issue or municipal supply problem, with common culprits including partially closed valves, failing pressure regulators, mineral buildup, and hidden leaks.
- Normal residential water pressure should be between 40–80 PSI. If your home’s pressure falls below 40 PSI, it’s time to investigate the cause.
- Arizona’s hard water can accelerate mineral buildup inside pipes and fixtures, restricting water flow and causing pressure to decline over time.
- Professional plumbing help may be needed if pressure is low throughout the house, your water meter moves when no water is being used, or simple fixes fail to restore normal pressure.
If your shower barely rinses shampoo out of your hair or your kitchen faucet feels more like a trickle than a stream, you’re likely dealing with low water pressure. In some cases, it can point to a hidden plumbing problem, not just a city water supply issue.
Arizona’s hard water and aging plumbing systems make pressure problems especially common. Since 2016, Target Plumbing has helped Phoenix Valley homeowners identify and fix the root cause of low water pressure in their houses. From mineral buildup to leaks and failing pressure regulators, this guide outlines the common causes of low water pressure and how to fix them.
What “Low Water Pressure” Actually Means
Measured in PSI (pounds per square inch), water pressure is the force that moves water through your home’s plumbing system. Most homes should maintain water pressure between 40 and 80 PSI. When pressure drops below 40 PSI, showers, faucets, and appliances suffer.
How to Measure Your Home’s Water Pressure
You can check your water pressure using a simple pressure gauge attached to an outdoor spigot. If the reading is below 40 PSI, your pressure is low and requires further diagnosis. If pressure is between 40 and 80 PSI, it is within the normal range, in which case the issue may be limited to a specific fixture rather than the entire house.
City Supply vs. Your Private Plumbing
Low water pressure is often caused by either a city water supply issue or a problem within your home’s plumbing. Contact your water utility if your neighbors or nearby homes have the same problems. If limited to your house, inspect your shutoff valves, the pressure regulator, or plumbing lines to find the cause.
Most Common Causes of Low Water Pressure in a House
If you’re wondering, “Why is my water pressure low?” the cause is usually one of a handful of common plumbing issues. The key is identifying whether the problem is isolated to a fixture or more widespread throughout your plumbing system.
Partially Closed Shutoff Valves
A partially closed shutoff valve can significantly reduce water pressure throughout your home. In Arizona, the main shutoff is often located in an outdoor utility box or near where the water line enters the home. Confirm it’s fully open, but do not adjust the utility-owned meter valve.
Failing or Incorrectly Set Pressure Regulator
A failing pressure-reducing valve (PRV) can cause sudden pressure drops, fluctuations, or a gradual decline in pressure. While minor adjustments are possible, worn regulators usually need to be replaced.
Mineral Buildup and Clogged Pipes
Arizona’s hard water can leave mineral deposits inside pipes, faucets, and showerheads, restricting water flow over time. Cleaning a clogged aerator may restore pressure, but older galvanized pipes often require repair or repiping.
Leaks in the Supply Line
Hidden leaks can reduce pressure throughout the house, increase water bills, or cause wet spots in the yard. If your water meter continues moving when all fixtures are off, call a licensed plumber to locate and repair the leak.
Low Water Pressure in Just One Fixture
If only one faucet or shower has weak pressure while the rest of your home is fine, the problem is almost always at or near that fixture, not in your main water line. That’s good news: these fixes are often quick and inexpensive.
Low Water Pressure in the Shower
The most common cause is a showerhead clogged with mineral buildup, especially in the Phoenix area, where hard water leaves scale in the small spray holes. Other causes include:
- A flow restrictor inside the showerhead that limits water flow
- A failing shower valve cartridge or pressure-balancing valve, which controls the mix of hot and cold water
Try this first: remove the showerhead and soak it in white vinegar for a few hours to dissolve the scale. If pressure is still weak with the showerhead off, the problem is likely the valve, and it’s time to call a plumber.
Low Water Pressure in the Kitchen Sink
A weak kitchen faucet is usually caused by a clogged aerator, the small screen at the tip of the faucet that catches sediment and scale. Other causes include:
- A worn or clogged faucet cartridge
- A partially closed shutoff valve under the sink
- A kinked supply line or pull-down sprayer hose
Try this first: unscrew the aerator, rinse out any debris, and soak it in vinegar. Then check that both shutoff valves under the sink are fully open.
Low Hot Water Pressure Only
If your cold water flows normally but your hot water is weak, the problem is likely with your water heater or the hot water lines. Common causes include:
- Sediment buildup in the water heater tank or outlet
- A partially closed shutoff valve on the water heater
- Scale buildup in hot water pipes, which happens faster with Arizona’s hard water
- For tankless water heaters, a clogged inlet filter screen or scale in the heat exchanger
If low hot water pressure affects every faucet in your home, have your water heater inspected and flushed. Tankless units in hard water areas typically need regular descaling.
Sudden vs. Gradual Pressure Loss
How quickly the problem appeared is an important clue:
- Sudden pressure loss often points to a water main break, a city supply issue, a failed pressure regulator, or a valve that was accidentally closed.
- Gradual pressure loss over months or years usually means mineral buildup in pipes and fixtures, aging galvanized pipes, or a pressure regulator slowly wearing out.
If you notice a sudden drop throughout your home, check with neighbors and your water utility before calling a plumber. It may be a temporary issue on the city’s side.
How to Diagnose Low Water Pressure Step by Step
Follow these steps to determine whether the low water pressure issue is isolated to a fixture, widespread throughout your home’s plumbing, or coming from the municipal water supply.
Step 1 — Single Fixture or Whole House?
Start by determining where the problem occurred. If low pressure only affects one fixture, such as a kitchen faucet or toilet, the issue is usually local. Check the fixture’s shutoff valve, inspect the supply line for kinks, and look for mineral buildup in the aerator or fixture components.
- For low water pressure in a kitchen faucet, remove the aerator from the faucet tip and rinse out debris or soak it in vinegar before reinstalling.
- For a toilet with low water pressure, make sure the shutoff valve behind the toilet is fully open and inspect the fill valve inside the tank for debris.
- If pressure is low throughout the house, continue to Step 2.
Step 2 — Check the Main Shutoff and PRV
Next, verify that your main shutoff valve is fully open. In Arizona, it’s commonly located in a ground-level utility box outside the home or in the garage near where the water line enters the home.
Locate the pressure-reducing valve (PRV), the bell-shaped device installed on the main water line. If accessible, check whether the adjustment screw has moved, and note its current position before making any changes. If the shutoff valve and PRV appear normal, continue to Step 3.
Step 3 — Rule Out a Leak or Municipal Issue
Check your water meter with all fixtures turned off. If the meter continues moving, a leak is likely diverting water and reducing pressure throughout the house.
If the meter remains still, contact your water utility and ask whether there are active water main breaks, maintenance projects, or pressure issues in the area.
If there is no utility problem and pressure remains low throughout the home, it’s time to call a licensed plumber for a professional diagnosis.
Common Mistakes Homeowners Make With Low Water Pressure
Many homeowners make well-intentioned fixes that fail to address the real cause of low water pressure.
Installing a Whole-House Filter Without Accounting for Pressure Drop
A whole-house or under-sink low-pressure water filter can worsen existing pressure problems when a dirty cartridge restricts flow. If your home already has borderline pressure, replace filter cartridges every 3–6 months and verify that incoming pressure is adequate before installing a filtration system.
Cranking Up the PRV Without Understanding the Risk
Increasing pressure at the PRV may seem like a quick fix, but excessive pressure can strain pipes, fixtures, and appliances. If pressure keeps dropping, replace the regulator instead of continuing to adjust it.
Ignoring the Problem Because “It’s Not That Bad”
Mineral buildup, pipe corrosion, and slow leaks often cause a gradual decline in pressure. These problems worsen over time and drive up repair costs when ignored.
When to Call a Plumber for Low Water Pressure
If you’ve ruled out simple fixes and pressure is still low, the issue may require professional diagnosis.
Signs the Fix Is Beyond DIY
Some pressure problems involve leaks, aging pipes, or supply line issues that homeowners cannot safely confirm without the right tools.
- Pressure is low throughout the house, even with all valves fully open.
- The water meter moves when all fixtures are off.
- The PRV was replaced recently, but the pressure keeps dropping.
- The home has galvanized steel pipes and was built before 1970.
- Pressure drops when multiple fixtures run at once.
What a Plumber Will Do (and What It Costs)
A licensed plumber will compare pressure at the meter and inside the home, inspect the PRV, check accessible joints for corrosion, and use a pipe camera if they suspect an internal blockage. Costs vary by project, home size, and pipe material.
Low Water Pressure FAQs
What is normal water pressure for a house?
Normal residential water pressure ranges from 40–80 PSI, with 60 PSI considered ideal. Pressure below 40 PSI can cause low water pressure in the house and affect fixture performance.
Why is my water pressure low only in the morning?
Morning pressure drops often occur during peak demand when many neighbors use water at the same time. If pressure remains low all day, the cause is likely inside your home’s plumbing.
Can a clogged water filter cause low pressure?
Yes. A dirty filter cartridge can restrict water flow and reduce pressure throughout the house, especially if pressure is already borderline.
Why is my kitchen faucet pressure low, but my shower is fine?
A clogged faucet aerator is usually the culprit. Remove the aerator, rinse out debris, and reinstall it before investigating other causes.
How do I know if my pressure regulator is bad?
A failing PRV often causes sudden pressure drops, fluctuations, or a steady decline in pressure. Most pressure regulators last about 10–15 years before replacement becomes necessary.