Quick Answer:
High water pressure can push small, worn seals and diverter paths to leak only when the shower feels strong. Measure your house pressure if you can; if it’s high, that explains why a small defect only shows up under stronger flow. Test by reducing flow to see whether the leak stops — if it does, pressure is the likely culprit.
Why This Happens
Plumbing fixtures are designed for typical household pressures. When pressure rises above the normal range, tiny gaps in seals, cartridges, or diverters that normally hold back water can be forced open. That makes leaks appear only at higher flow settings. Small issues that are hard to notice at low flow become obvious when the shower is on full blast.
Two common patterns:
- Diverter or tub-spout leaks: a worn diverter or seat lets water escape when pressure builds.
- Valve cartridge or seal leaks: worn cartridges may hold under low flow but fail under high pressure.
Related reading that may help with similar symptoms: Tub spout leaks when washer runs and Leak only upstairs bathroom.
Step-by-Step What to Do
1. Observe and isolate
- Run the shower at high pressure and note where the leak appears (tub spout, handle trim, ceiling below, etc.).
- Turn the shower down to a lower flow setting and check whether the leak decreases or stops.
2. Measure house pressure if possible
- Use a simple pressure gauge on an outdoor hose bib or a laundry hookup. Read the gauge with all indoor fixtures off for an accurate static reading.
- Typical comfortable pressure is about 40–60 psi. Readings consistently above 70–80 psi are high and can stress fixtures and seals.
3. Test with reduced flow to confirm pressure is the trigger
- Lower the shower flow (use the shower’s lower setting, move the handle toward low, or open another faucet to lower system pressure) and watch the leak point.
- If the leak stops or becomes insignificant when flow is reduced, pressure is likely making a small defect visible.
4. Simple temporary steps while you decide next moves
- Use lower flow settings for now to limit water damage.
- Place a bucket or towels under the leak to protect finishes.
- Note any stains or water travel paths for the plumber, especially if water shows up downstairs or in ceilings.
What Not to Do
- Don’t ignore high pressure — pressure can damage fixtures, plumbing joints, and appliances over time.
- Don’t assume tightening visible screws or applying a quick sealant will fix a pressure-related leak permanently.
- Don’t delay getting help if pressure is high or fluctuating; if pressure is high/unstable, a plumber is appropriate to diagnose and correct it.
When to Call a Professional
- If your pressure gauge shows consistently high or wildly fluctuating readings.
- If you see water damage, staining, or leaks that run into ceilings or walls.
- If reducing flow stops the leak but you want a permanent fix — replacing cartridges, diverters, or installing/adjusting a pressure reducing valve is best done by a pro.
- If you can’t find the leak source or it returns after simple checks.
Safety Notes
- Shut off the water at the shower or the home’s main valve if a leak gets large or risks damaging floors and ceilings.
- Turn off electricity to affected areas if water reaches outlets, switches, or fixtures before touching anything.
- Work on valves and cartridges with care — slippery conditions and sharp edges can cause injury. Stop and call a pro if you’re unsure.
Common Homeowner Questions
- Q: Can high pressure ruin shower seals?
A: Yes. Sustained high pressure shortens the life of seals and cartridges and makes small leaks worse. - Q: Will reducing flow fix it permanently?
A: Reducing flow is a good temporary measure but doesn’t repair worn parts or fix an overpressure problem long-term. - Q: Can I lower house pressure myself?
A: You can adjust a pressure reducing valve if you have one and know how, but if you don’t, call a plumber to avoid mistakes that affect the whole house.
For more related articles, see the Tub Spout Leaks When Shower Is On hub.