Quick Answer:
After a city water outage, sediment and mineral bits often move through the pipes and collect in aerators, shower screens, and valve seats. First flush and clean the aerator and showerhead screen. If the shower still drips when the valve is off, the cartridge or its seat may be scratched or scored and will likely need professional service.
Why This Happens
When supply pressure drops or is shut off, loose particles that normally sit in the mains or in your pipes can shift. When flow resumes those particles travel and can hang up in small openings such as:
- aerator screens on sinks
- showerhead strainers or screens
- the valve body around the cartridge or ceramic seats
Even a small nick or scratch on a valve seat or cartridge sealing surface can allow a slow drip when the valve is closed. If you also recently did work on the plumbing, check related fixtures such as Dripping started after remodel for other causes.
Step-by-Step What to Do
1. Run and observe several fixtures
- Open cold and hot taps briefly at different points in the house to help flush the main and pipe runs. Watch for cloudy water or sand that clears.
- If you see sediment coming out, continue flushing until water runs clear.
2. Flush and clean the aerator and showerhead screen
- Unscrew the sink aerator and showerhead or remove the shower screen if accessible.
- Rinse the parts under strong running water. Use a soft brush to remove visible debris.
- Reinstall and test the shower valve. Many drips stop after this step.
3. Test the valve carefully
- Turn the valve on and off slowly to see whether the drip appears while operating or only when closed.
- If the drip returns immediately after closing, sediment may have scratched the sealing surfaces.
4. Inspect the cartridge if you are comfortable
- Shut off water to the fixture (use local shutoffs or the main) before removing the trim and cartridge.
- Look for scoring, grooves, or visible debris on the cartridge or the seat area inside the valve body. Clean any loose grit, but don’t force or file the parts.
- If surfaces appear damaged, the cartridge or seat may need replacement or professional refinishing.
5. Special checks
- If the problem affects only one location, consult guidance for a single fixture—see Drip only upstairs shower for related troubleshooting steps.
- If flushing and inspection don’t stop the drip, plan for service rather than attempting aggressive DIY fixes.
What Not to Do
- Don’t keep cycling the valve rapidly after an outage without first flushing aerators and screens; that can grind sediment further into seats.
- Don’t try to hammer, file, or reshape valve seats without proper tools and knowledge—this can make leaks worse.
- If dripping persists, a plumber is appropriate; don’t keep attempting high-risk repairs if you’re unsure.
When to Call a Professional
- If the drip continues after you’ve flushed fixtures and cleaned screens.
- If you find a scored cartridge or damaged seat—these parts often require replacement or specialized repair.
- If the leak is behind the wall, causing damage, or you cannot shut off the water safely.
Safety Notes
- Shut off the water supply before removing cartridges or internal valve parts to avoid uncontrolled flow.
- Be cautious of hot water scalds when flushing hot lines—run cold first and use gradual tests.
- If electrical outlets, appliances, or finished surfaces are exposed to leaking water, stop and call a professional to prevent damage and hazard.
Common Homeowner Questions
- Why did this start after the outage? Sediment and pressure changes move debris into small openings; when flow resumes it can lodge in screens or scratch seats.
- Will cleaning the aerator fix the drip? Often yes for minor sediment; if the drip continues the valve seat or cartridge may be damaged.
- Can I replace the cartridge myself? You can if you have the right parts, shutoffs, and comfort level; if the seat is scratched or the job is behind a wall, call a plumber.
For more related articles, see the Dripping Showerhead After Shutoff hub.