Water pressure affects every plumbing fixture in your home — how well your shower rinses shampoo, how fast your dishwasher fills, how quickly your toilet tank refills. Ideal residential water pressure is between 45–80 PSI (pounds per square inch). Outside that range — too low or too high — creates problems ranging from inconvenience to serious pipe and appliance damage.
Low Water Pressure
Causes
- Clogged aerators or showerheads — mineral deposits from hard water clog the small screens in aerators and showerhead nozzles, dramatically reducing flow from those fixtures
- Partially closed shut-off valves — the main shut-off or fixture-specific valves may not be fully open after a repair
- Pipe corrosion and buildup — galvanized steel pipes accumulate internal scale that narrows the water pathway over decades
- Municipal pressure issue — if your neighbors also notice low pressure, the problem is with the utility, not your home
- Slab or underground leak — water escaping through a pipe crack reduces pressure throughout the house
- Pressure regulator failure — a faulty pressure reducing valve (PRV) may be set too low or failing
Fixes
Cleaning aerators: Unscrew the aerator from the faucet tip (hand-tight, lefty-loosey). Soak in white vinegar for 30 minutes, scrub with an old toothbrush, and reinstall. Do the same for showerheads — fill a plastic bag with vinegar and rubber-band it over the showerhead overnight.
Adjusting the PRV: Your pressure reducing valve is usually located where the main supply enters the house, near the main shut-off. It has a screw on top — tightening it increases pressure, loosening decreases it. Check pressure at a hose bib with a pressure gauge ($10–$15 at any hardware store) before and after adjusting.
Replacing the PRV: If adjusting doesn't help, the PRV itself may need replacement. This is a plumber's job — a new PRV costs $50–$120 in parts; installation runs $100–$350 including labor.
High Water Pressure
High pressure feels great in the shower but silently damages your home. Chronic high pressure stresses pipe joints and fittings, causes water hammer (the banging noise when you shut off a tap quickly), reduces the lifespan of washing machine hoses, dishwashers, and water heaters, and can cause dripping faucets by forcing water past worn valve seats.
What's Normal vs. High
- 45–80 PSI: Normal residential range
- 80–100 PSI: High — install a pressure regulator
- 100+ PSI: Dangerously high — immediate plumber attention
Testing Your Pressure
Attach a pressure gauge to any outdoor hose bib or washing machine connection. Take the reading in the morning before significant water use. If it's above 80 PSI, you need a pressure reducing valve (PRV) or an adjustment of the existing one.
Expansion Tanks
If your home has a closed water supply system (backflow preventers mean water has no way to expand back toward the street), thermal expansion when your water heater heats water can cause pressure spikes. An expansion tank — a small tank installed on the cold water inlet to the water heater — absorbs this expansion. Many plumbing codes now require them. If your water heater is dripping from the pressure relief valve, a failing expansion tank is often the cause.