Why Is My Water Pressure Low? How to Find the Actual Cause

What should my water pressure be, and how do I check it?

Between 45 and 60 psi. EPA WaterSense recommends incoming service pressure in that band for efficient water use and proper system function, and calls it the optimal range for water-using fixtures and appliances [1][2].

To check it, get a water pressure test gauge from a hardware store. Turn off all water-using fixtures and systems in the house, screw the gauge onto a hose bibb and turn the water on fully [2]. EPA's technical sheet also lists the cold-water faucet for the washing machine hookup, or a cold-water faucet on the first floor, as places to attach it [1].

If the house has a pressure-reducing valve, take a second reading indoors. Florida's plumbing code exempts service lines to outside hose bibbs and hydrants from the pressure-reduction requirement [5], so an outside tap can read higher than the house actually gets.

Two readings change what comes next. If it is much lower than 45 psi, EPA says you may need to find and fix a leak [2]. If it is above 80 psi, you have the opposite problem — see the high-pressure question below [1][5].

Why is the water pressure low in the whole house?

Work down the supply line in this order: the street or the house, the main shutoff, the pressure-reducing valve, any filter or softener, the pipe itself, and a leak.

Street or house. The City of Tampa's test is to open an outside spigot: if the pressure there is good, the problem is in the home's plumbing [6]. If the drop was sudden and the neighbours lost pressure too, call the water utility first — a main break or a repair on the street affects everyone on that line.

The main shutoff, or a valve after a repair. A valve left partly closed reads like a failing supply, and opening it is the simplest fix on this list.

The pressure-reducing valve. If the house has one, its job is to hold pressure in the 45–60 psi range [2]. One that is set too low, has drifted or has failed gives you a weak house. EPA's annual maintenance checklist says to check your service water pressure and adjust or replace the valve if necessary [4].

Filters and the softener. The City of Tampa suggests bypassing a water softener to see whether the pressure improves; if it does, you may have a clogged filter [6]. A clogged sediment prefilter drops pressure across itself, which is what the gauges on a filter housing are there to show. Iron and manganese deposits also build up in pipelines, pressure tanks, water heaters and water softeners, which reduces the available quantity and pressure of the supply [3].

The pipe itself. Old galvanized steel narrows from the inside as it corrodes and collects deposits. Cleaning does not reverse that; repiping does.

A leak. Pressure much lower than 45 psi can mean a leak somewhere in the home [2]. EPA's check: read the water meter while no water is being used, read it again later with everything still off, and if the reading has changed you probably have a leak [2].

Why is the water pressure low in only one faucet or shower?

Because the restriction is at that fixture, not in the supply — so it is not a pressure problem, and no equipment needs buying. Check the aerator screen and the shutoff valves under the sink first.

The City of Tampa notes that customers with low pressure often find debris clogging their faucet aerator screens [6]. EPA suggests inspecting faucets for scaling or calcium buildup and using white vinegar or another cleaning product to remove buildup that may be restricting flow, and inspecting showerheads for scale the same way [2].

If a shower is still weak after the head is clean, the cartridge in the shower valve is the next suspect. A faucet that lost flow right after utility work on the street usually has sand or debris in its screen.

Is 80 psi water pressure too high?

Above 80 psi, yes. Florida's plumbing code requires a pressure-reducing valve with a strainer where static water pressure in a building exceeds 80 psi, to bring it down to no more than 80 psi [5], and EPA notes that most US plumbing codes set the same threshold [1].

EPA's technical sheet explains why: pressure in supply mains can reach 100 psi or more, and high water pressure can damage plumbing piping, fixtures and appliances, and can lead to increased water consumption, premature equipment failure and risk of leaks [1]. If your pressure is much higher than the 45–60 psi range, EPA suggests having a professional adjust or install a pressure-reducing valve to help keep it at 60 psi [2].

So a gauge is worth putting on even when nobody is complaining about pressure: if the house has had repeat leaks, high pressure is one of the first things to rule out.

One consequence worth knowing before it surprises you: a pressure-reducing valve creates a closed system, and EPA says to consult local plumbing codes on whether thermal expansion then needs to be addressed [1]. That is why a new valve and an expansion tank are often discussed together.

What should the water pressure be on a well?

EPA WaterSense says single-family homes supplied by groundwater wells should use a pressure tank set at 60 psi [1].

So on a well, low pressure points at the pressure tank, its pressure switch or the pump rather than at a utility — a different investigation from a city supply, and the point where the well contractor's part of the work begins. Iron and manganese deposits in pressure tanks and pipelines also reduce the available pressure [3].

Do I need a plumber for low water pressure?

Not always — if it is one aerator or showerhead, cleaning it may be all it needs. For anything else, the gauge reading decides what kind of job it is.

We measure before we quote. If the gauge reads well under 45 psi, we look for a leak or a valve that is not fully open. If it reads above 80, we talk about a pressure-reducing valve and thermal expansion, not about your shower head. If it reads in range and only one shower is weak, we will tell you it is a cartridge job and not a repipe.

The number is the part that makes the conversation honest, and it is the part you can get before anyone arrives.

Low pressure in Tampa Bay: is it the city or my house?

Start with one outside tap. The City of Tampa tells its water customers that if the pressure at an outside spigot is good, the problem is in the home's plumbing and a plumber is the right call; it also suggests bypassing a water softener to see whether the pressure improves [6].

The same page notes that customers with low pressure often find debris clogging their faucet aerator screens, and that people in apartments or condos who do not pay their water bill directly to the City should contact their building manager [6].

The spigot test works the same way in Clearwater and the rest of Pinellas, with one Florida catch: an outside hose bibb is exempt from the pressure-reduction requirement [5], so if the house has a pressure-reducing valve, a good reading at the spigot does not tell you what the house gets after the valve. Compare it with an indoor cold tap.

Two patterns we see locally. Houses built for one bathroom and remodelled to three often keep the original service line, so the gauge reads fine with everything closed but the flow drops when two fixtures run — a sizing problem, not a pressure problem. And in older block houses, a shutoff valve that was not fully reopened after a repair is a common cause.

FAQ

Sources

We review and cite. We do not reproduce a paper or a manual — follow the links for the originals.

1. [1]Service Water Pressure (WaterSense Technical Reference Manual, General Features) — U.S. Environmental Protection Agency, WaterSense · 2023Government or standards body · quoted: mains can reach 100 psi or more; high pressure can damage piping, fixtures and appliances; most US codes require a PRV above 80 psi; 45–60 psi recommended; well pressure tank set at 60 psi; consult local codes on thermal expansion after a PRV; where to attach the gauge
2. [2]Home Maintenance — WaterSense — U.S. Environmental Protection Agency · 2026Government or standards body · quoted: fixtures operate at their optimum at 45–60 psi; how to test at a hose bibb; much lower than 45 psi may mean a leak; much higher, have a professional adjust or install a PRV; water-meter leak check; vinegar on scale that restricts flow
3. [3]Iron and Manganese Removal — North Dakota State University Extension · 2025University extension · WQ1030, revised December 2025: deposits build up in pipelines, pressure tanks, water heaters and softeners, reducing available quantity and pressure
4. [4]Maintenance Checklist for a Water-Efficient Home — U.S. Environmental Protection Agency, WaterSense · 2024Government or standards body · once a year: check service water pressure and adjust or replace the pressure-regulating valve if necessary; inspect showerheads and faucets for scale
5. [5]Florida Building Code, Plumbing, 8th Edition (2023) — Section 604.8, Water Pressure-Reducing Valve or Regulator — Florida Building Commission · 2023Law / code · a pressure-reducing valve with strainer is required where static pressure within a building exceeds 80 psi; exception for service lines to sill cocks and outside hydrants; text confirmed on a public copy (UpCodes) because the ICC viewer loads by script
6. [6]Water Pressure Issue — City of TampaGovernment or standards body · open an outside spigot: good pressure there means the problem is in the home's plumbing; debris in aerator screens; bypass a softener to test for a clogged filter; apartments and condos go through the building manager