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Plumbing depends on the building

Shared risers, roof tanks, house traps, sump pumps: what your plumbing looks like, and who is responsible for it, depends on the kind of building you live in or manage.

NYC apartmentsRentals, co-ops, condosBrownstones & rowhousesCast iron, house trapsHigh-rise buildingsRisers, tanks, pumpsTwo- to four-familySmall landlordsSuburban housesSump pumps, lateralsCo-ops & condosWho fixes what
§ 01

Building types compared

General characteristics only. Any individual building may differ because of renovations, original design and maintenance history.

How plumbing typically differs by building typeEducational comparison; not an assessment of any specific property.
Building typeTypical configurationCommon maintenance concernsAccess considerationsShared infrastructureCommon service needs
Brownstone / rowhouseStreet-pressure supply; cast-iron stack; house trap in cellarScale and rust in cast iron; galvanized supply; possible lead service lineCellar access; finished interiorsUsually noneMain line clearing, repiping, sewer repair
Prewar apartment buildingHouse pump + roof tank above ~6 stories; vertical risers and stacksRiser leaks; stack clogs; aging valvesInside walls between units; board or agent approvalRisers, stacks, central hot waterStack cleaning, riser/valve work, leak tracing
Postwar apartment buildingPump systems; risers; mixing valvesShower valves; pressure balancing; valve replacementBuilding rules; scheduled shutoffsRisers, central plantValve and fixture work, leak detection
High-risePressure zones via roof tanks or booster pumps; pressure-reducing valvesLeaks between floors; pressure complaintsFreight elevators, insurance certificatesEverything verticalLeak detection, PRV and valve work
CondoVaries with building ageIn-unit fixtures and branch linesBoard approval, certificatesCommon elements per declarationIn-unit repairs; leak responsibility questions
Co-opVaries with building ageAs building type; proprietary lease defines the splitAlteration agreementsPer proprietary leaseRepairs; renovation plumbing
Suburban houseMunicipal water or private well; sewer lateral or septicWater heater; sump pump; roots in lateral; frozen pipesGenerally easyNoneWater heaters, sump pumps, sewer laterals, main water line
§ 02

How water reaches the top floor

Water supply and drainage in a ten-story apartment buildingDiagram 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. Some buildings use booster pumps instead of a roof tank, and zoning differs by building.