Weak flow at one tap or the whole house? Here's how to tell whether it's a clogged aerator, a failing regulator, or a bigger supply-line problem.
Weak water pressure is one of the most common calls we get — and the fix is almost never as simple as "turn up a valve." The first step is figuring out whether it's one fixture or the whole house, because that tells you where the problem lives. Here's how we diagnose and fix low pressure.
Isolate the problem: one fixture or the whole house?
Turn on the cold tap at a faucet that's been bugging you, then walk to another faucet on a different floor and run that one too. If the pressure is low only at a single fixture, the problem is local to that fixture. If it's low everywhere, you have a whole-house issue — and the cause is upstream.
One-fixture problems: start at the aerator
Nine times out of ten, low pressure at a single tap is a clogged aerator. The little screen at the end of the spout catches sediment, mineral scale, and debris — and in hard-water areas like Guelph and Brantford it builds up until the flow is a trickle. Unscrew the aerator (a cloth and pliers, gently), rinse it backward under the tap, and scrub the screen with an old toothbrush. If it's crusted with scale, soak it in vinegar for an hour. Screw it back on and the flow usually returns to normal.
The same principle applies to a showerhead — mineral scale is the usual suspect when a shower dribbles. Unscrew the head, soak it in vinegar overnight, and scrub the nozzles. If it's still weak, the showerhead itself may be flow-restricted or simply worn; a replacement is inexpensive.
The fixture valve
Every fixture has a shut-off valve (angle stop) under the sink or behind the toilet. If that valve is only partly open — sometimes from a previous repair — the flow is restricted. Check that the valves under the problem fixture are fully open (turn counterclockwise until they stop). A valve that won't turn, or that's crusty and weeping, is worth replacing.
Whole-house problems: check the obvious first
If pressure is low everywhere, walk through the easy causes before assuming the worst:
- The main shut-off valve. It should be fully open. A gate valve that's partly closed (or a gate that's broken off inside and stuck halfway) restricts flow to the entire house. If the main valve is a gate valve and it's stiff, don't force it — call us.
- The pressure regulator. Many homes have a pressure-reducing valve (PRV) where the water line enters the house. It keeps municipal pressure at a safe level for your plumbing. A failing PRV can stick low and starve the whole house. You can check the set pressure with a cheap gauge screwed onto a hose bib — it should read between 40 and 60 psi (50–55 is ideal). If it's well below that, the PRV needs adjusting or replacing.
- A partially closed valve you forgot about. It happens — a valve closed for a repair and not reopened. Check the main and any valves near the water heater.
When it's the pipes
If the valves and regulator are fine and the pressure is still low across the house, the problem is likely in the pipes — and the cause depends on the age and material of your home's plumbing.
Galvanized steel supply lines (common in homes built before the 1960s) corrode from the inside out. The inside of the pipe narrows with rust and mineral buildup until water barely flows — and it happens gradually, so you adapt to the low pressure until it's truly miserable. There's no fix for a corroded galvanized line except replacement; the good news is a modern PEX or copper re-pipe restores full pressure and lasts decades.
A hidden leak in the main supply line between the meter and the house is the other whole-house culprit. If your pressure dropped suddenly and your water bill climbed, check the meter with everything off — if the low-flow indicator is still spinning, water is leaving the system somewhere. A main-line leak wastes water you're paying for and starves the house.
The one to rule out first
Before you assume the pipes are bad, screw a pressure gauge onto a hose bib and read it. If the static pressure (everything off) reads 50–60 psi but the flow drops to a trickle when you open two taps, the problem is flow, not pressure — and that's usually a restriction (a corroded line, a clogged filter, a closed valve) rather than a supply problem. Reading the gauge tells you which direction to chase.
If you're not sure where to start, give us a call. We'll measure the pressure and the flow, isolate the cause in minutes, and tell you whether it's a five-minute aerator clean or a supply-line replacement — with a fixed price before any work starts.
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