If only one faucet has low pressure, the cause is usually a clogged aerator or cartridge at that fixture. If the whole house has low pressure, check that the main valve is fully open, then look at the pressure-reducing valve, hidden leaks, or aging galvanized pipes narrowed by corrosion. Utility-side problems can also lower pressure across a neighborhood.
Reviewed by Ron Olsen, Master Plumber, certified in Washington
What Lowers Water Pressure
- Clogged aerator or shower head
- Mineral buildup restricts the flow at one fixture.
- Partly closed valve
- The main valve or a fixture shutoff valve may not be fully open.
- Failing pressure-reducing valve
- A worn PRV can drop the pressure for the whole house.
- Corroded pipes
- Galvanized steel pipes narrow inside as they corrode.
- Leaks
- A hidden leak diverts water and lowers pressure.
What You Can Safely Check
- Check whether the problem is one fixture, hot water only, or the whole house.
- Unscrew and clean faucet aerators and shower heads.
- Make sure the main valve and the fixture shutoff valves are fully open.
- Ask neighbors whether they have low pressure too.
- If only hot water is weak, the problem may be at the water heater.
When to Call a Plumber
Call a plumber if the whole house has low pressure, if the pressure dropped suddenly, or if you have older galvanized pipes. A plumber can test the pressure, replace a failing pressure-reducing valve and look for leaks.
The repair is usually part of pipe repair & repiping, which explains what the plumber does and what affects the cost.
Galvanized Pipe by City
What our city pages say about galvanized pipe:
- San Leandro, CA: Original steel pipe rusts from the inside, cutting pressure and turning water brown.
- Birmingham, AL: With a median home built in 1965, corroded drain stacks and narrowed supply lines cause slow drains, leaks and low pressure.
- Minneapolis, MN: With a median home built in 1951, corroded supply lines and drain stacks are common.
- Chicago, IL: Older homes may still have galvanized supply piping or a lead service line, which can reduce pressure and should be evaluated for replacement.
- Grand Rapids, MI: With a median home built in 1953, corroded drain stacks and narrowed supply lines cause slow drains and weak pressure.
- Rochester, NY: With a median home built in 1938, corroded stacks and narrowed supply lines cause leaks, clogs and weak pressure.
- Atlanta, GA: Early-1900s homes in in-town neighborhoods may still have galvanized lines with low pressure and pinhole leaks.
- Kansas City, MO: Early-1900s homes often have corroded drains and supply lines that cause slow drains and low pressure.
Other Pipe Repair & Repiping Problems
Low Water Pressure Questions
What is normal household water pressure?
Most homes run between about 40 and 80 psi. A plumber can measure it with a gauge on an outdoor spigot.
Why is only my hot water pressure low?
Sediment in the water heater, a partly closed valve at the heater, or scale in the hot water lines can restrict the flow.