Quick Answer:
If your bathroom sink is noticeably slow only first thing in the morning, it’s usually a mild partial clog or settling of debris in the trap or stopper overnight. Test the drain at different times, clean the stopper, and, if needed, remove and inspect the P‑trap before calling a plumber.
Why This Happens
- Hair and soap scum can settle and pack into the P‑trap or around the pop‑up stopper overnight, which can make the drain slower after a long idle period.
- Standing water or debris that moves during daytime use may temporarily clear or shift, so the drain seems faster later in the day.
- Vent or minor partial clogs farther down the line can cause slow drainage at certain times, especially if air gets trapped.
- New fixtures or recent work sometimes change flow patterns; see Slow drain after installing new faucet for what to check if you recently had work done.
Step-by-Step What to Do
1. Observe and compare
- First thing in the morning, run a measured amount of water (for example, a 1‑liter jug) and time how long it takes to drain using a phone or timer.
- Repeat the same test mid‑day after regular use. This direct comparison helps confirm whether the problem really is time‑of‑day dependent.
2. Clear the stopper and immediate debris
- Remove the pop‑up stopper or lift out the strainer and clean away visible hair and gunk. This often restores flow quickly.
- Flush with hot tap water for a minute to help push soap scum forward.
3. Flush the drain
- Boil water safely and pour it slowly into the drain in two or three stages (do not pour boiling water on some plastic fittings—use caution). This can break up soft clogs and move residues.
4. Inspect and clean the P‑trap
- Place a bucket under the P‑trap, loosen the slip nuts, and remove the trap to check for trapped hair and debris. Clean it and reseal carefully.
- Keep the area dry and have a towel ready. Tighten the nuts snugly but don’t overtighten plastic fittings.
5. Check for venting or downstream issues
- If the trap is clean and the sink is still slow only in the morning, run other fixtures and listen for gurgling noises; that can indicate a vent or deeper line issue.
- If you recently shaved or used heavy soap and see similar slow behavior, check the article about Slow drain after shaving for related causes.
6. Re-test at the same times
- After cleaning, repeat the morning vs midday drainage test to confirm whether the problem is resolved.
What Not to Do
- Do not judge based on one use — repeated tests at the same times are important before deciding it’s a persistent problem.
- Do not pour commercial drain cleaners down the sink as a first step; they can damage pipes and create hazardous fumes.
- Do not force metal tools down the drain or use an aggressive auger without experience—this can damage fixtures or finishes.
When to Call a Professional
- Multiple fixtures are slow or you have frequent backups.
- There is sewage smell, water backup, or gurgling from vents.
- After cleaning the trap and stopper the sink is still slow, or you’re not comfortable taking the P‑trap apart.
Safety Notes
- Wear gloves and eye protection when cleaning traps and handling debris.
- Use a bucket under the trap to catch spills and protect floors from water damage.
- If you use any chemicals despite the advice, follow label directions carefully and ventilate the area. Consider a professional if you’re unsure.
Common Homeowner Questions
- Is it normal for a sink to be slow only in the morning? Short answer: Yes, often it’s due to settled hair or soap in the trap that shifts with daytime use.
- Will hot water fix it permanently? Short answer: Hot water can help clear soft buildup temporarily but won’t remove solid hair clogs; cleaning the stopper or trap is usually needed.
- Can I fix this myself? Short answer: Many homeowners can clear the stopper or clean the P‑trap safely; call a plumber if the problem persists or involves multiple fixtures.