Low water pressure in a house comes down to one of three things: a restriction at a single fixture (a clogged aerator or showerhead), a restriction affecting the whole home (a partially closed valve, a failing pressure-reducing valve, or corroded pipes), or a supply problem (a leak, or low pressure from the utility). Ten minutes of testing tells you which one you have. Normal household pressure is 40–60 psi; below 40 feels weak and below 30 means something is wrong.
Below is a quick diagnostic to narrow it down, then the fix for each cause — including the ones you can do yourself in an afternoon and the ones that signal a leak you need to find fast.
Step 1: Is it one fixture, or the whole house?
- One faucet or shower is weak, the rest are fine → the problem is at that fixture. Skip to “Single-fixture causes.”
- Only hot water is weak → the problem is in the water heater or its shutoff valve. See “Hot water only.”
- Everything is weak → the problem is at the main supply, the pressure regulator, or the pipes. See “Whole-house causes.”
- Pressure dropped suddenly → check whether a valve was bumped closed, whether the utility is working nearby, and whether your water meter is spinning with everything off (a leak).
Step 2: Measure your actual pressure
Buy a hose-bib pressure gauge ($10–$15) and screw it onto an outdoor spigot, ideally the one closest to where the water enters the house. Make sure nothing is running, then open the spigot fully.
- 40–60 psi: normal. If it still feels weak, you have a flow problem (a restriction), not a pressure problem.
- Below 40 psi: low. Check the main valve and pressure regulator first.
- Above 80 psi: too high — that’s a different problem that damages appliances and needs a pressure-reducing valve.
Then test flow: time how long a fixture takes to fill a one-gallon bucket. A kitchen faucet should manage it in about 30–40 seconds. If pressure is normal but flow is weak, something in the pipe or fixture is restricting it.
Single-fixture causes
1. Clogged aerator or showerhead
Unscrew the aerator from the faucet tip (or the showerhead from its arm), soak it in white vinegar for an hour, scrub the screen, and reinstall. With Tampa Bay’s hard, mineral-heavy water, this needs doing once or twice a year. It’s the fix for most single-fixture complaints.
2. Partially closed fixture shutoff valve
Check the valves under the sink or behind the toilet. They should be fully open (counterclockwise). Valves get nudged during cleaning or repairs.
3. Failing cartridge or clogged supply line
A faucet cartridge can clog with debris or scale, especially after the water was shut off for repairs. Pulling the cartridge and flushing it (or replacing it) restores flow. Braided supply lines can also kink or collapse internally.
Hot water only
4. Sediment in the water heater or a closed heater valve
Check that the cold-water inlet valve on top of the heater is fully open. If it is, the tank has probably accumulated sediment that’s restricting the outlet, or the dip tube has broken. Flushing the tank helps; if the heater is over 10 years old, the restriction is often scale in the outlet nipple and it’s time to talk about replacement.
Whole-house causes
5. The main shutoff valve isn’t fully open
Find your main valve (usually where the water line enters the house, or at the meter near the street). A gate valve with a round handle should be turned counterclockwise until it stops; a ball valve with a lever should be parallel to the pipe. A valve left half-closed after a repair is one of the most common causes of sudden whole-house low pressure.
6. A failing pressure-reducing valve (PRV)
If your home has a bell-shaped PRV on the main line, it can fail closed or clog internally after 10–15 years. Symptoms: pressure is fine at the street but low at the house, or pressure fluctuates wildly. Some PRVs can be adjusted with the screw on top (clockwise increases pressure); a failed one needs replacing.
7. Corroded or scaled pipes
Galvanized steel supply pipe — standard in homes built before the 1960s and common through the 1970s — rusts from the inside, narrowing a three-quarter-inch pipe to the diameter of a pencil over decades. The tell-tale signs are pressure that has declined gradually over years, rusty water after the house sits, and flow that’s worse on the second floor or at the far end of the house. There’s no cleaning fix; the answer is repiping, either the worst sections or the whole house.
8. A leak somewhere in the system
Turn off every fixture and appliance, then watch your water meter for five minutes. If the low-flow indicator (a small triangle or star) spins, water is leaving the system somewhere. In slab-foundation homes across Tampa Bay, that’s often a supply line leaking under the concrete — you may also notice a warm spot on the floor, a higher water bill, or the sound of running water when nothing is on. This one is urgent: a slab leak undermines the foundation and feeds mold.
9. The utility or a neighbor
Ask neighbors if their pressure dropped too, and check your utility’s website for main breaks or maintenance. Homes at the end of a line or on high ground get lower pressure to begin with. If the utility confirms your pressure at the meter is low and can’t improve it, a booster pump at the house is the solution.
When to call a plumber
Call right away if the meter spins with everything off, if you find a warm or damp spot on a slab floor, or if the pressure drop came with discolored water — those point to a leak or pipe failure that gets more expensive every day it runs. Also call if you have a PRV that needs replacing, if you suspect galvanized or polybutylene pipe, or if you’ve cleaned the fixtures and the flow is still weak. A plumber can measure pressure at the meter and at the house in a single visit and tell you exactly where the drop is happening.
Frequently Asked Questions
What is normal water pressure for a house?
40 to 60 psi is the normal range, with 50 psi a comfortable target. Below 40 psi feels weak at showers and faucets; above 80 psi is too high and shortens the life of water heaters, faucets, toilet fill valves, and appliance hoses. Florida’s plumbing code requires a pressure-reducing valve when supply pressure exceeds 80 psi.
Why is my water pressure low all of a sudden?
The most common causes of a sudden drop are a main or fixture shutoff valve that was partially closed, a utility main break or maintenance nearby, a failed pressure-reducing valve, or a new leak — check your water meter with everything off. A sudden drop in hot water only usually points to the water heater.
How do I increase water pressure in my house?
First confirm what you have with a hose-bib gauge. If pressure is normal but flow is weak, clean aerators and showerheads and check for restrictions. If pressure is genuinely low, open the main valve fully, adjust or replace the pressure-reducing valve, and if the utility’s supply pressure is simply low, install a booster pump.
Can a water leak cause low water pressure?
Yes. A leak large enough to affect pressure — typically a slab leak, a failed underground service line, or a burst pipe in a wall — also shows up as a spinning meter with all fixtures off and a rising water bill. Treat that combination as urgent.
Does low water pressure mean my pipes are corroded?
It can, if the pressure has declined gradually over years, you have galvanized steel pipe, and you see rusty water after the house sits unused. Corroded pipe narrows from the inside and can’t be cleaned; repiping the affected runs is the fix.
Pressure still weak — or is the meter spinning?
Llona Plumbing is a licensed, family-run plumber (License #CFC1431902) serving Tampa, St. Petersburg, Clearwater, Brandon, New Port Richey and the rest of Hillsborough, Pinellas, Pasco and Hernando counties. If your whole house has low pressure, your meter moves with everything off, or your home still has galvanized or polybutylene pipe, call (813) 477-1870 — we answer 24/7, we give you a straight price before work starts, and a licensed plumber shows up with the parts to handle pressure testing, leak detection and repiping in one visit. Water damage compounds by the hour, so don’t wait on a problem that’s getting worse.
