Quick Answer:
If a single fixture has good pressure in the morning but is weak at night, the problem is most likely an intermittent restriction or something that uses or affects that branch during the evening. Start by tracking the time-of-day pattern, check moving parts such as a pull-down hose or weight, and clean the aerator and cartridge for intermittent debris before assuming whole-house demand is the cause.
Why This Happens
When pressure changes only at certain times, it usually means something local to that fixture is changing between those times. Common causes:
- Intermittent blockage that shifts with water flow or temperature (sediment, mineral flakes, or a loose piece of debris).
- A kinked or pinched pull-down hose or a weight that moves and presses the hose against a port when the spray head is stowed.
- Another device or appliance on the same branch turning on at night — a timed valve, irrigation system, or circulating pump — stealing flow or changing pressure regulation.
- Valve or cartridge issues that let small debris lodge temporarily and then clear after sitting (this is why cleaning the cartridge helps).
If valve work was done recently at the fixture, also consider related valve issues; for more on that, see Low pressure after valve replacement. If a toilet on the same branch behaves oddly at other times, compare notes with fixtures like a toilet — for a related read, see Toilet fills slowly but others are normal.
Step-by-Step What to Do
Step 1 — Track the time-of-day correlation
- Keep a simple log for several days: note pressure at the fixture at the same morning and evening times (for example, 7am and 9pm).
- Test other nearby fixtures at the same times to see if the issue is isolated to one branch or affects multiple outlets.
Step 2 — Check for something else using that branch
- Ask household members about timers or automatic devices (irrigation, hot-water recirculators, dishwasher, washing machine) that might run in the evening.
- Turn off suspected timed devices and compare the fixture’s pressure again at night.
Step 3 — Inspect the pull-down hose and weight
- Extend the spray head and look for kinks where the hose bends. With the spray head stowed, gently move the hose to see if a weight or fitting shifts and pinches the line.
- Operate the handle and spray head while watching the hose movement; an intermittent restriction often shows when the hose rests in a certain position.
Step 4 — Clean the aerator and cartridge
- Remove and inspect the aerator for trapped debris. Soak in vinegar if mineral scale is present and rinse thoroughly.
- If the faucet has a cartridge or ceramic disc assembly, follow the manufacturer steps to remove and rinse it. Small particles can lodge and cause pressure to fluctuate.
Step 5 — Check supply stops and simple valves
- Confirm the shutoff under the sink is fully open and not partially closed or loose.
- Operate the shutoff a few times to feel for rough movement or intermittent closing that could affect flow at certain times.
Step 6 — Simple test to reproduce the issue
- At a time when pressure is normally poor, run the fixture for a minute and then shut it off for a few minutes. Try again to see if the pressure returns — patterns like this suggest debris shifting or a timed device cycling.
What Not to Do
- Don’t assume it’s ‘demand’ if only one fixture is affected—look for an intermittent restriction (hose/weight) first.
- Don’t remove or alter pressurized parts without shutting off the water supply first.
- Don’t replace major equipment (pressure regulator, whole-house components) before confirming the problem is not local to one fixture.
When to Call a Professional
- Pressure issues persist after you’ve cleaned the aerator/cartridge and checked the hose and valves.
- You find signs of corrosion, damaged supply lines, or a stuck valve you can’t safely operate.
- Multiple fixtures show the same time-of-day pressure drop, suggesting a larger system or supply problem.
- There’s active leaking, water damage, or you’re uncomfortable disassembling the faucet cartridge.
Safety Notes
- Shut off the local supply valve before removing cartridges, aerators, or working on connections.
- Use basic hand tools and avoid using excessive force on plastic parts; they can crack and cause leaks.
- If you suspect electrical components (timers, pumps), switch off power before inspecting those devices and call an electrician if unsure.
Common Homeowner Questions
- Why does only one faucet lose pressure at night? — It’s usually a local, intermittent restriction or a timed device on the same branch, not whole-house demand.
- Will cleaning the aerator and cartridge likely fix it? — Often yes; many intermittent problems are caused by small debris that lodges and then clears.
- Can I test this without tools? — Yes: track times, run the fixture alongside others, watch the pull-down hose, and ask household members about timers before disassembling anything.
For more related articles, see the Low Pressure at Single Fixture hub.