Quick Answer:
If a fixture only drips after you use hot water, the leak is most likely coming through the hot side of the mixing valve or cartridge. Start by confirming the behavior with the hot and cold shutoffs, then inspect or replace the cartridge/seals on the hot sealing surface. If the problem continues or you’re not comfortable doing the work, call a licensed plumber.
Why This Happens
Most modern faucets and showers use a mixing valve or cartridge that controls hot and cold separately inside the same assembly. Heat and mineral deposits make hot-side seals, O-rings, or seats wear faster. After you run hot water the valve parts expand and the worn hot-side surface can leak until pressure and temperature settle back down. Cold-only paths aren’t affected the same way, so you see the drip only after hot water use.
Step-by-Step What to Do
1. Reproduce and observe
- Run hot water from the fixture until it gets hot, then shut the handle or lever off.
- Note whether the drip starts immediately after and how long it continues.
2. Compare hot-only vs cold-only shutoff behavior
- If you have separate shutoff valves under the sink or behind the fixture, close the cold shutoff and run hot only. Turn hot off and watch for a drip.
- Then open the cold and close the hot shutoff, run cold only, close it and compare. If the drip appears only after hot use or when hot remains connected, the hot-side path is the suspect.
3. Isolate the valve type
- Identify whether the fixture uses a cartridge, ceramic disc, compression stem, or ball valve. Single-lever cartridges and ceramic discs are common and have replaceable cartridges or seats.
4. Turn off water and relieve pressure
- Shut off both hot and cold supply valves and open the fixture to drain any pressure before disassembly.
5. Inspect and clean
- Remove the handle and cartridge or stem. Look for damaged O-rings, scored sealing surfaces, mineral buildup, or warped plastic parts. Clean deposits gently with vinegar or a manufacturer-recommended cleaner.
6. Replace worn parts that affect the hot side
- If only hot triggers the drip, replace the cartridge or the seals that form the hot sealing surface. In many cartridges you can replace O-rings or the whole cartridge cheaper and faster than attempting repairs to the valve body.
7. Reassemble and test
- Reinstall new parts, restore water, and test hot-only and cold-only behavior again. Confirm the drip no longer appears after hot use.
8. If it still drips
- Persistent dripping after you’ve replaced cartridges or seals usually means the valve body’s seat or sealing surface is damaged or corroded and requires professional repair or replacement of the valve assembly.
What Not to Do
- Don’t assume hot-only drips will go away—hot-side sealing issues typically worsen; if it persists, a plumber is appropriate.
- Don’t use glue, epoxy, or tape inside a valve as a permanent fix; these can prevent proper sealing and later repairs.
- Don’t overtighten valves or connections trying to stop a drip; overtightening can damage seats, threads, or plastic parts.
When to Call a Professional
- If you’ve confirmed the drip only follows hot use and replacing the cartridge/seals didn’t stop it.
- If the valve body is corroded, cracked, or the sealing seat is damaged—these require professional tools or valve replacement.
- If the leak is large, affects cabinets, or you are uncomfortable working on hot supply lines. Also call a pro if the fixture is part of a complex shower system or hidden mixing valve inside a wall.
Safety Notes
- Always shut off both hot and cold supplies and open the fixture to relieve pressure before taking anything apart.
- Hot water can scald—test carefully and avoid working on fixtures immediately after heavy hot use.
- Use the right tools and avoid forcing parts. If you encounter unexpected rusted or frozen fittings, stop and get professional help to avoid damaging the plumbing.
Common Homeowner Questions
- Dripping after filter install — If you recently changed plumbing accessories, check those connections first; a new filter or fitting can change pressures and reveal a weak hot-side seal.
- Showerhead drips after turned off — If the drip is at the showerhead, the shower valve cartridge or seat is likely the issue; testing hot vs cold shutoffs helps confirm it.
- Will replacing the cartridge fix it? — Often yes for cartridge-style valves, but if the valve seat or body is damaged you may still need a valve replacement or professional repair.
For more related articles, see the Dripping Showerhead After Shutoff hub.