Quick Answer:
If your sink next to the shower runs fine but the shower gives a weak stream, start by removing the showerhead and running water from the bare shower arm for 10–15 seconds. If the flow from the arm is strong, clean or replace the showerhead. If the flow from the arm is weak, the problem is likely the shower valve, cartridge, or the stop valves feeding that fixture and will need more hands-on attention or a plumber.
Why This Happens
- Mineral buildup or debris inside the showerhead can restrict spray passages while nearby fixtures remain unaffected.
- The shower valve or cartridge can be partially blocked or worn, reducing flow only at that outlet.
- Dedicated shutoff (stop) valves to the shower or tub may be partly closed or failing, limiting flow downstream.
- Plumbing supply lines that feed only the shower can have a problem (scale, pinch, or partial blockage) while the rest of the house is fine.
Step-by-Step What to Do
1. Compare fixtures
- Turn on the nearby sink and any other fixtures on the same bathroom supply to confirm they have normal pressure.
- Don’t assume a whole-house issue when only the shower is weak.
2. Remove the showerhead and test the arm (10–15 seconds)
- Unscrew the showerhead by hand or with a wrench (protect the finish with a cloth).
- Turn the shower on and run water from the bare shower arm for 10–15 seconds.
- If flow is strong from the arm: the showerhead is the likely cause — clean or replace it.
- If flow is weak from the arm: stop here and move to valve and stop checks.
3. Clean or replace the showerhead
- Soak the head in a vinegar solution or use a commercial descaler to remove mineral deposits, then rinse and test.
- If cleaning doesn’t restore flow, replace the showerhead — modern heads are inexpensive and simple to swap.
4. Check the shower stop valves and supply
- Locate any shutoff (stop) valves for the shower or tub—often behind an access panel or in a nearby closet.
- Ensure they’re fully open. If a valve is hard to turn or appears damaged, it can restrict flow even when “open.”
- If you have two-handle controls, check both hot and cold supplies separately by briefly opening and feeling flow from the arm.
5. Inspect the valve or cartridge
- A failing cartridge or valve seat can block flow. If the shower arm flow was weak, this is a common cause.
- Replacing a cartridge is a common plumbing repair but requires turning off the water, removing trim, and matching the exact part.
- If you’re not comfortable disassembling the valve, call a pro rather than forcing parts and causing damage.
What Not to Do
- Don’t assume the whole house has low pressure—test the shower arm first rather than drawing that conclusion.
- Don’t force or overtighten fittings when removing the showerhead; you can damage threads or finishes.
- Don’t keep trying to fix a weak flow from the arm yourself if it remains weak after the basic checks—if flow is weak there, a plumber is appropriate.
When to Call a Professional
- If the bare shower arm has weak flow after testing, and you’re not able to locate or access the valve or stops.
- If the valve or cartridge appears corroded, stuck, or you don’t have the right replacement part.
- When access to the plumbing requires removing tiles, cutting into a wall, or complex valve work—these are best left to a plumber.
- For related situations, check guidance on Shower pressure suddenly dropped or Tub spout pressure weak but sinks fine where applicable.
Safety Notes
- Turn off water at the main or the fixture’s stop valves before taking apart valves or cartridges.
- Protect finishes by using a cloth when using tools on fittings and avoid excessive force.
- If you suspect a gas water heater issue or scalding risk when testing hot water, stop and call a professional.
Common Homeowner Questions
- Why did this happen suddenly?
Mineral scale or debris can accumulate over time and suddenly change flow when a passage becomes mostly blocked. - Can I clean the valve myself?
You can inspect stops and clean accessible parts, but cartridge replacement is more involved; know your limits. - Will replacing the showerhead fix it?
Yes if the arm flow is strong. If the arm flow is weak, replacing the head won’t help.