When people think about plumbing, they often imagine long pipes hidden behind walls. In reality, many water changes start with the small, visible parts right at your sink or shower.
Fixtures—like faucets and showerheads—contain internal parts that wear over time. Inside many faucets are cartridges that control flow and temperature. As these age, they can cause changes in pressure, uneven hot and cold mixing, or odd tastes from materials breaking down.
Aerators, the small screens at the end of faucets, are especially important. They collect debris, sediment, and mineral buildup. When water suddenly looks cloudy, sprays unevenly, or releases particles, a clogged aerator is often the reason. Cleaning or replacing it can immediately fix the issue.
Flex lines—the short hoses connecting fixtures to the wall—are another common source of changes. Older flex lines can degrade internally, affecting taste or releasing small particles into the water stream.
In showers, shower bodies and valves control pressure balance. When these wear out, you may notice sudden temperature swings, weak flow, or delayed hot water.
None of these issues come from the city supply. They happen at the very last stage of water delivery—inside your unit.
Before assuming a larger problem, it’s always worth asking:
Is it happening at one faucet or all of them?
Does removing the aerator change anything?
Is the issue hot water only?
Often, the explanation is much closer than people think.
In older buildings, what you can’t see matters just as much as what you can.
Many NYC and NJ buildings still contain original plumbing from decades ago. Over time, pipes change internally—even if they look fine on the outside. Materials used in the past behave differently than modern ones, especially as they age.
As water moves through older pipes, it can pick up:
Rust particles
Mineral residue
Metallic tastes
Temporary discoloration
This is especially noticeable after water sits unused for several hours. Morning discoloration is often a sign of water interacting with internal plumbing overnight—not a city issue.
Behind the walls, pipes may:
Narrow slightly from buildup
Release sediment during pressure changes
React differently to temperature shifts
When nearby construction or hydrant use changes water flow, older pipes are more likely to release material. That’s why older buildings often show visible changes first—even when the city supply hasn’t changed.
This doesn’t mean the water is unsafe. It means the building’s internal system is aging and responding to normal system activity.
Understanding this helps renters and homeowners know when an issue is structural—and when it’s simply part of living in an older building.
Brownstones and prewar buildings behave differently from newer apartments—and for good reason.
Many of these buildings have layered plumbing histories. Pipes may have been replaced in stages over decades. One section could be original, another upgraded in the 1980s, another modernized recently.
This creates mixed plumbing eras inside the same building.
What does that mean in real life?
Water may behave differently on different floors
One unit may see discoloration while another doesn’t
Hot water delays may vary by location
In brownstones especially, vertical risers serve multiple floors. Changes on one floor—like fixture replacements—can affect pressure and flow elsewhere.
Prewar buildings often rely on shared hot water systems. This explains why hot water may look darker or take longer to clear than cold water.
Newer buildings tend to have more uniform materials and layouts, which leads to more predictable behavior. Older buildings are perfectly livable—but they’re less uniform.
Unpredictability does not equal danger. It means responses vary.
Once people understand this, many “mystery” water issues start making sense.
When something changes at the tap, it’s natural to assume the problem is the city. In reality, most tap issues originate inside the building or unit.
Before assuming a city-wide problem, it helps to check a few things:
Is the issue happening at every faucet, or just one?
Is it hot water only or both hot and cold?
Do neighbors see the same thing?
Does the issue clear after running water briefly?
Has there been recent plumbing work in the unit or building?
If only one fixture is affected, the cause is almost always local. If the whole building sees the issue, it’s usually internal plumbing or recent maintenance.
City-wide issues tend to:
Affect many buildings at once
Be acknowledged publicly
Resolve through flushing or maintenance
Most individual tap changes don’t fit that pattern.
Knowing what to check first saves time, reduces stress, and helps you ask the right questions—whether that’s to a superintendent, plumber, or building manager.
Your tap is the end point of many systems:
City supply
Building infrastructure
Unit-level plumbing
Understanding how they interact makes water changes far less mysterious.
KnowYourTap.org helps you figure out where to look before assuming the worst.