Fixing Low Cold Water Pressure in Shower
Did your shower lose cold water pressure after cartridge replacement? Learn why this happens and how to restore proper flow safely.
Older two-handle showers often develop drips over time. Replacing cartridges inside the hot and cold knobs usually solves leaks, but sometimes new issues appear.
In this case, the homeowner replaced both cartridges to stop a severe drip. The leak was fixed, but when the water supply was turned back on, the pressure balance was off. The hot water had a strong flow, but the cold side lost almost all pressure. Even with the cold knob fully open, the water was too hot for comfortable use.
All main water valves in the basement were checked and confirmed open. Other fixtures in the home had normal water pressure. The problem seemed isolated to the shower cold line.
Question:
Why would a shower lose cold water pressure after cartridge replacement, and how can it be fixed?
Answer:
The most likely cause is a blockage inside the new cold cartridge or debris pushed into the shower valve during installation. When water is shut off and cartridges are replaced, sediment or old washer fragments can shift into the valve body. This restricts flow on one side only. Removing the cold cartridge, flushing the line, and reinstalling should restore pressure. If not, the cartridge may be defective and should be replaced again.
Other possible causes include a misaligned cartridge, a damaged O-ring, or scale buildup in the shower valve. Since the rest of the house has normal cold water pressure, the issue is isolated inside the shower valve.
For more details, check this Family Handyman shower repair guide. You may also want to watch this video on replacing shower cartridges.
I’m Chris Mayer, writing for Plumbing 101.
