Low flow appears limited to the hot-water side
Normal cold flow with weak hot flow points beyond the showerhead toward the hot-water system, mixing valve, or hot-side plumbing.
Why this result fits
- Cold flow is normal or clearly stronger.
- The restriction appears when the control moves toward hot.
- A showerhead-only blockage would ordinarily affect both temperatures.
What to do now
Stop if temperature is unstable
End the test if the water becomes unexpectedly hot or alternates sharply between hot and cold.
Note other hot-water symptoms
Briefly record whether bathroom or kitchen hot taps are also weak and whether hot water is discolored or slow to arrive.
Contact maintenance
Report the hot-versus-cold difference without opening the valve, heater, or access panel.
Stop and escalate if
- Water becomes dangerously hot or temperature fluctuates sharply.
- The water heater or nearby piping is leaking.
- Hot water is discolored, has an unusual odor, or is unavailable throughout the unit.
What not to do
- Do not open or adjust the mixing valve.
- Do not service the water heater.
- Do not remove anti-scald or pressure-balancing components.
Message you can send to maintenance
Cold shower flow is normal, but flow becomes weak when I select hot water. [Other hot fixtures are/are not] affected. I stopped testing and have not opened the valve or water heater.
Help prevent a repeat
- Report hot-water changes early.
- Keep the area around any accessible water heater clear so leaks can be noticed safely.
If this does not match
Sources and review date
- Troubleshooting water pressure and flow — Portland Water Bureau
Content last reviewed: under the Apartmentwise methodology.