Quick Answer:
A sudden drop in shower pressure is usually caused by a clogged showerhead, a problem with the shower valve or cartridge, a supply valve partly closed, or a wider water-supply issue. Start by checking other taps in the house and testing flow at the shower arm (with the head removed). Those two quick checks will tell you if the issue is local to the shower or affects the whole home.
Why This Happens
- Mineral scale or debris clogging the showerhead or built-in flow restrictor.
- A failing mixing valve or cartridge that limits flow when set to certain positions.
- Partially closed supply or main shutoff valves after recent work.
- Problems at the water heater (if only hot pressure is low) or a municipal supply pressure drop affecting multiple homes.
- Recent plumbing work that disturbed pipes or left debris, which can cause shower low pressure after plumbing repair.
Step-by-Step What to Do
1. Check other fixtures right away
- Turn on a cold tap (kitchen or laundry) and a hot tap and note if either has reduced flow. If several fixtures are weak, it’s likely a whole-house issue.
- Ask a neighbor if they have low pressure too—this can tell you if the municipality is the cause.
2. Test flow at the showerhead with the head installed
- Run the shower and watch for sputtering, steady weak flow, or air. Note whether the drop happened suddenly while you were showering or between showers.
- Try both hot and cold positions if the handle lets you isolate them.
3. Remove the showerhead and test the arm (the supply outlet)
- Unscrew the head from the shower arm by hand or with a cloth and adjustable pliers if needed. Be careful not to twist the arm.
- Run the water briefly from the open arm. If the flow at the arm is strong, the showerhead is clogged and needs cleaning or replacement.
- If the flow at the arm is weak, the problem is upstream (valve, supply pipes, or municipal supply).
4. Check shutoff valves and recent work
- Locate any local shutoffs for the shower (an access panel or valves near the tub). Ensure they’re fully open.
- If pressure dropped after any recent plumbing work, debris may be in the pipes or a valve may not be fully open.
5. Narrow down hot vs. cold
- Test hot-only taps elsewhere in the house. If only hot is weak, the water heater or hot-side plumbing is likely at fault.
- If only the shower’s hot side is weak, you may need help diagnosing the mixing valve—this is covered by issues like low pressure only on hot side at shower.
What Not to Do
- Don’t keep swapping showerheads without testing pressure at the arm; if pressure is weak there, a plumber is appropriate.
- Don’t force or hammer on the shower arm or valves to “free” them; that can break fittings and cause leaks.
- Don’t remove the mixing valve cartridge or make complex repairs unless you’re comfortable with plumbing and have shut off the water first.
When to Call a Professional
- If the arm flow is weak (you removed the head and still have poor pressure).
- If only one temperature side is affected and it points to a valve or water-heater issue.
- If the drop follows recent plumbing work and basic checks don’t find the cause.
- If you find a leak or you’re unsure how to safely access or operate shutoff valves.
Safety Notes
- Turn off water at the main if you discover a leak you can’t control.
- Be careful when removing the showerhead—use a cloth to protect finishes and avoid damaging the arm.
- Avoid standing on slippery wet surfaces while working; use a steady step stool if needed and keep the floor dry when possible.
Common Homeowner Questions
- Q: Why did pressure drop suddenly while I was showering?
A: Sudden drops are often caused by a clog, a valve shifting, or a temporary municipal issue. - Q: Can I clean the showerhead myself?
A: Yes—soak it in vinegar or disassemble and rinse to remove mineral buildup; test the arm first to confirm the head is the issue. - Q: Is low pressure and a leak related?
A: They can be related if a leak reduces supply pressure; always fix leaks promptly and call a plumber if you can’t locate the source.