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Why is my water pressure low?

A shower that trickles, a sink that takes forever to fill. Where the low pressure shows up tells you a lot about the cause.

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Takes about a minute. Tell us what's happening, what kind of building it is, and the town or neighborhood.

Narrow it down first
  1. One fixture or all of them? Check cold and hot at several taps.
  2. Just you, or the whole building? Ask a neighbor.
  3. Sudden or gradual? Sudden drops can mean a leak, a closed valve or a building problem.
  4. Hot only? Then look at the water heater or the hot-water system.

01In short

Low pressure at one fixture is usually that fixture: a clogged aerator or showerhead, or a worn cartridge. Low pressure everywhere in a house often means old galvanized pipes narrowed by corrosion, a partly closed main valve, a failing pressure regulator or a leak. In apartment buildings above about six stories, water comes from a roof tank or booster pumps, and the top floors have the least pressure.

Why top floors get less pressure in tank buildingsDiagram D2
  • Cold water
  • Hot water
  • Drain / waste / sewer
  • Vent
Schematic of water supply and drainage in a ten-story New York apartment building City water enters the basement. A house pump lifts water through an up-feed pipe to a roof tank. Gravity then feeds a down-feed riser that branches to each floor, so pressure is lowest on the top floors closest to the tank. In some buildings, lower floors are fed directly by street pressure. A drain stack collects waste from every floor and runs down to the building sewer, with a vent through the roof. Configurations vary; some buildings use booster pumps instead of a tank. STREET 10987654321 BASEMENT roof tank house pump lowerpressure higherpressure 12345678
  1. 1City water enters at street pressure. In NYC that is typically enough to reach about six stories
  2. 2House pump lifts water from the basement
  3. 3Up-feed line to the roof tank
  4. 4Roof tank stores water; gravity creates the pressure below
  5. 5Down-feed riser: one shutoff often serves a whole vertical line of apartments
  6. 6In some buildings, lower floors are fed directly from street pressure (dashed)
  7. 7Drain stack: shared by every apartment stacked above
  8. 8Vent through the roof

Simplified, not to scale.

02Common signs

  • Weak flow at one tap or showerhead
  • Weak flow everywhere, worse when two fixtures run
  • Pressure that changes during the day
  • Rusty or brown water along with weak flow
  • Hot water weaker than cold

03Possible causes

Where it shows up and what it may mean
PatternPossible causes
One fixture onlyClogged aerator or showerhead, worn cartridge, partly closed fixture valve
Whole house, gradualCorroded galvanized supply pipes, mineral buildup
Whole house, suddenMain shutoff partly closed, failing pressure-reducing valve, leak, utility work
Hot water onlySediment in the water heater, valve or mixing valve problem
Top floors of a buildingRoof tank level, house pump or booster pump problem
Whole buildingPump failure, tank problem or city main work
Home on a wellPressure tank, pressure switch or well pump problem

Corrosion inside old galvanized pipe narrows the opening over decades.

04What you can safely check

  • Unscrew and rinse the faucet aerator or showerhead
  • Make sure the main shutoff and fixture valves are fully open
  • Check the water meter for movement with everything off (a hidden leak)
  • Ask neighbors or the super whether the building has a problem

05When to call a plumber

  • Pressure is low throughout the house
  • You see rusty water or leaks at threaded joints (galvanized pipe)
  • A pressure-reducing valve or well equipment needs adjusting or replacing
  • The building's pump or tank system is involved

A plumber measures static and flowing pressure, checks valves and the pressure regulator, and identifies pipe material. Old galvanized piping is often the cause in older homes; see pipe repair & repiping.

06By building type

Prewar & high-rise buildings
Roof tanks or booster pumps supply upper floors; top floors get the least pressure. Report building-wide drops to management.
Brownstones & older houses
Galvanized supply pipes narrow over decades; repiping restores flow.
Suburban houses
Pressure-reducing valves and, on wells, pressure tanks are common causes.

07Local considerations

In New York City, street pressure typically reaches about six stories; taller buildings use roof tanks or pumps. More than half of NYC homes are in buildings constructed before 1947, so galvanized supply pipe is common.

Renting in NYC? Building owners are generally responsible for plumbing repairs in rental apartments. Tell the super or managing agent; if repairs aren't made, you can contact 311. In co-ops and condos, the proprietary lease or declaration decides who fixes what.

08Frequently asked questions

Why is my top-floor apartment's pressure so weak?

In buildings with roof tanks, pressure comes from gravity and is lowest on the floors closest to the tank. Some buildings add small booster pumps for top floors. Ask management.

Will replacing galvanized pipes fix low pressure?

If corrosion inside the pipes is the cause, yes. A plumber can confirm by checking flow at different points.

Sources & review

Last reviewed . General information, not legal or engineering advice. Rules change and individual buildings differ.

  1. CooperatorNews, Water pressure in high-rises
  2. NYC Rent Guidelines Board, 2023 Housing Supply Report (NYC HVS 2023)

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