Quick Answer:
If the tub spout leaks only when you run the shower after de-winterizing, first confirm any seasonal shutoffs are fully open and that air has been purged from the lines. Next, repeatedly cycle the diverter (the shower/tub switch) to free a stiff seal that may have dried or stuck during winter storage. If the leak continues or the diverter stays stuck, call a plumber — stiff seals can fail suddenly and leak into walls or under the floor.
Why This Happens
- Many homeowners close seasonal shutoffs or drain lines for winter. If a shutoff wasn’t fully reopened, trapped air can cause unusual pressure and brief leaks when water is restored.
- Rubber seals and O-rings in the diverter and spout can dry, shrink, or stick when unused for months. Cycling the parts can often free them, but a seal that is cracked or brittle will leak under pressure.
- High pressure or a partially open valve can change flow patterns and cause water to bypass a worn seal. If you notice leaks only under certain pressure conditions, that detail matters for diagnosis.
Step-by-Step What to Do
1. Confirm seasonal shutoffs are fully open
- Find any winter shutoff valves for the bathroom (often under the sink, in a crawl space, or near the main line). Slowly open them all the way.
- Open the tub faucet and let water run for a minute to help purge air from the line.
2. Purge air from the system
- With the tub and shower running, cycle hot and cold a few times. Listen for sputtering and wait until the flow is steady. This helps remove trapped air that can change valve behavior.
3. Cycle the diverter repeatedly
- Operate the diverter (pull, push, twist, or lift depending on your type) back and forth 10–20 times while water is running. This often loosens a stiff seal or deposits that formed during winter.
- Try cycling gently at first; don’t force parts that feel like they will break.
4. Check for persistent leaking patterns
- If the spout leaks only when the shower is on, note whether it’s when pressure is high or after the valve is fully opened.
- If the leak appears behind the wall, stains on ceilings below, or persistent dripping into a cavity, stop and call a pro rather than continuing to run water.
5. If you must disassemble, proceed cautiously
- Turn off the local shutoff or the main water before disassembling a spout or valve trim.
- Only remove trim you feel comfortable with. If parts are corroded or unclear, a plumber can avoid causing more damage.
What Not to Do
- Don’t assume winter leaks will resolve on their own—stiff seals can fail suddenly and cause more damage.
- Don’t force a stuck diverter or pry aggressively; you can break the trim or internal pieces.
- Don’t keep running water into a leaking wall or floor cavity while hoping it improves—stop and seek help if the leak continues.
- If it sticks or leaks after basic cycling and purge steps, a plumber is appropriate rather than prolonged DIY attempts.
When to Call a Professional
- If cycling the diverter and confirming shutoffs and purges don’t stop the leak.
- If you see water damage, mold, or leaking behind walls or under floors — these situations need prompt professional repair to prevent structural damage. For issues that point to leak paths through the structure, consider reading more on Tub spout leaks behind wall.
- If the leak only appears at higher flow or pressure and you can’t correct it at the fixture, a pro can test valves and pressure; see notes on Leak only when shower pressure high.
Safety Notes
- Turn off water supply before removing hardware to avoid flooding.
- If you smell gas or see electrical issues near the leak, evacuate and call the appropriate emergency services — don’t work near those hazards.
- Wear eye protection and use basic hand tools only if you know how. Otherwise hire a qualified plumber.
Common Homeowner Questions
- Will running the shower more fix a stuck diverter? Sometimes; gentle repeated cycling can free a seal, but it won’t fix a cracked or brittle seal.
- Can a partially open winter shutoff cause leaks? Yes — trapped air and unusual pressure can cause temporary leaks until the line is fully purged and valves are fully opened.
- How long should I try DIY fixes before calling a plumber? If basic checks and cycling don’t stop the leak within an hour, or if there’s any sign of water damage, call a professional.
For more related articles, see the Tub Spout Leaks When Shower Is On hub.