Why Is My Water Pressure Low? Common Causes in Calgary Homes

Short answer: Start by checking whether it is one fixture or the whole house. One slow tap or shower is usually a clogged aerator or a scaled-up showerhead, often a five-minute fix. Low pressure everywhere points to a partly closed main valve, a failing pressure-reducing valve, scaled or aging pipe, or a leak on the service line.

That first clue tells you a lot before anyone opens a wall. Work through the checks below in order.

Flow chart for low water pressure: first ask if it is one fixture or the whole house. One tap or shower points to a clogged aerator or showerhead, often a five-minute fix. The whole house points to a partly closed main valve, a failing pressure-reducing valve, scaled or aging pipe, or a leak on the service line. — Start with one fixture or the whole house. A clogged aerator or showerhead is often a five-minute fix. Whole-house causes include a partly closed main valve, a failing pressure-reducing valve, scaled or aging pipe, and a leak on the service line.

Narrow it down

What you notice	Likely cause	What to do
One tap or shower only	Clogged aerator or showerhead, or a worn fixture cartridge	Unscrew and clean the aerator or soak the showerhead in vinegar
Hot water only, everywhere	Sediment in the water heater or a partly closed valve on the heater	Check the valve, then have the tank flushed
Whole house, came on suddenly	Main valve partly closed after work, or a failing pressure-reducing valve	Check the main is fully open. Call if it is
Whole house, getting worse over months	Scale or corrosion narrowing older pipe, or aging Poly-B	Book a pressure diagnosis
Pressure drops with no taps running, sound of running water, soggy yard	A leak, possibly on the service line	Call us, and call 311 if water is pooling outside

One fixture: the five-minute fixes

Aerator. Unscrew the tip of the faucet, rinse out the screen and soak it in vinegar if it is crusted. Calgary's hard water scales these up over time.
Showerhead. Soak it in vinegar overnight, then scrub the nozzles.
Fixture shut-off. Make sure the valve under the sink is fully open.

If that does not fix it, the cartridge inside the faucet or shower valve may be worn. That is a small repair.

The whole house: what to check

The main shut-off. If anyone has worked on the plumbing lately, the main may not have been opened fully.
The pressure-reducing valve. Many homes have one just after the main. When they fail, pressure can drop or swing. Normal household pressure is generally in the 40 to 60 psi range, and a plumber can test it with a gauge.
Aging pipe. Scale and corrosion narrow old pipe, and it usually gets worse, not better. Grey Poly-B is a separate reason to look. Here is how to check for it.
A leak. The City of Calgary lists a drop in water pressure, noise on the service line when no taps are running, and water pooling on the ground as signs of a service line leak. The homeowner is responsible for repairs on their side of the property line.

Safe to do yourself, and when to call

Safe to do yourself: cleaning aerators and showerheads, checking that fixture valves and the main are fully open.

Call a plumber: if the whole house is affected, the pressure keeps dropping, you hear water running when nothing is on, or you see water where it should not be.

Common questions

Why did my water pressure suddenly drop?

Check whether neighbours are affected, since City work can lower pressure for a while. If it is just your house, look at the main valve and the pressure-reducing valve, and watch for signs of a leak.

Can a water softener lower water pressure?

A clogged or undersized softener can. If the drop started after one was installed, have it checked.

Is low water pressure a sign I need to repipe?

Sometimes. If it is house-wide and has been getting worse for months, the pipe itself is often the cause. Here are five signs it is time.