Low water pressure in the house: how to find the actual cause
The first question is not "how do I boost the pressure." It is "how much of the house is affected." One fixture, one bathroom or the whole building each point at completely different problems.
Published 2026-08-30 by Floriano Plumbing Service · Serving all of Connecticut · (888) 809-6756
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Step one: narrow it down
Walk the house and check hot and cold separately at each fixture. Then place your result in one of these three buckets.
- One fixture, hot and cold. Almost always the aerator, the cartridge or the angle stop at that fixture.
- One fixture, hot only. Look at the water heater side - a partly closed valve, sediment, or a failing mixing valve.
- The whole house. Now you are looking at the main shut-off, the pressure reducing valve, the service line, or corroded supply piping.
The eight causes we see most
- Clogged aerators. Unscrew the tip of the faucet and look. Mineral grit is extremely common in hard water areas.
- A partly closed main shut-off. After any plumbing work, check the valve is fully open. It happens more than you would think.
- A failing pressure reducing valve. These have a service life. When they drift, whole-house pressure drops.
- Corroded galvanised pipe. Old steel supply lines close up from the inside. Pressure falls gradually over years.
- A hidden leak. Water escaping before it reaches your fixtures. Check the meter with everything off.
- A partially blocked or damaged water service line. Between the street and the house.
- Water heater sediment. Reduces hot-side flow specifically.
- Municipal supply pressure. Occasionally the street pressure itself is genuinely low, which changes the fix entirely.
The meter test
Turn off every tap and water-using appliance in the building, then look at the meter's low-flow indicator. If it is still creeping, water is going somewhere. That is a leak, and finding it is more urgent than the pressure complaint.
What the repair usually looks like
Aerator and cartridge work is a same-visit job. A pressure reducing valve replacement is a couple of hours. Corroded galvanised supply lines are the big one - at that point you are looking at a partial or whole-house repipe, and the honest comparison is repipe cost against the next few years of leak repairs and drywall.
Frequently asked questions
What is normal household water pressure?
Most homes sit comfortably between 45 and 70 psi. Much above 80 and you start damaging fixtures and appliances, which is what a pressure reducing valve exists to prevent.
Why is only my hot water pressure low?
That isolates the problem to the hot side: a partly closed valve at the heater, sediment in the tank, a scaled tankless heat exchanger, or a failing mixing valve.
Can low water pressure mean a leak?
Yes. A leak between the meter and the house is one of the classic causes of whole-house pressure loss, and it usually shows up on the bill at the same time.