One fixture or the whole house?
Start by checking several faucets, hot and cold, upstairs and down. The pattern tells you where to look.
- One faucet or shower only: a clogged aerator, showerhead or cartridge
- Hot water only: sediment in the water heater or a partly closed valve on it
- Everywhere: the pressure regulator, a partly closed main valve, a leak or buildup inside older pipes
- Neighbors too: a supply issue from the water utility
What you can safely check
Unscrew the aerator from a weak faucet and rinse out debris. Soak a showerhead in vinegar to dissolve scale. Make sure the main shutoff valve is fully open — valves are sometimes left partly closed after other work.
Pressure regulators
Many homes have a pressure-reducing valve where the main line enters. When one wears out it can drop pressure well below normal. A simple gauge on an outdoor hose bib shows the house pressure and whether the regulator is doing its job.
When professional help makes sense
If pressure is low throughout the house and the main valve is fully open, a plumber can test the pressure, replace a failing regulator and check for leaks or corroded galvanized pipe that has narrowed over the years.