Shower pressure worse after winterization

Shower flow reduced after winterization or seasonal shutoff reopening.

Quick Answer:

Most often this is caused by a seasonal valve left partly closed, an exterior cap still in place, or air trapped in the line. Start by confirming every seasonal valve you touched is fully open, check that any exterior or anti-freeze cap was removed, then flush the line with the showerhead off to push trapped air out.

Why This Happens

During winterization you normally shut off and/or cap exterior lines and sometimes use a shutoff or anti-freeze cap on interior shutoffs that control outdoor fixtures. If one of those valves was not reopened completely or a cap was left on, water flow is reduced. Another common cause is air trapped in the pipe after the line is opened again — air pockets can reduce or pulse the flow until they’re flushed out. If your problem looks different (for example, it began after home work), see **Shower pressure low after remodel** or, if the flow changes day-to-day, check **Shower pressure varies daily** for other possibilities.

Step-by-Step What to Do

1. Find and confirm every seasonal valve is fully open

  • Locate the shutoff(s) you used for winterization — these may be in a basement, crawl space, utility room, or behind an access panel near the shower. Some are labeled “seasonal” or “outside.”
  • Open each valve fully. For ball valves, the handle should be parallel to the pipe. For gate or globe valves, turn until it stops gently (don’t force beyond the stop).
  • If you’re not sure which valve controls the shower, open one at a time and test the shower between adjustments so you can identify the correct one.

2. Verify any exterior or anti-freeze cap was removed

  • Check outdoor hose bibs and any inline caps you installed. Remove plastic caps or threaded protective inserts that were used for winter protection.
  • If you used a brass or plastic isolation cap on an interior shutoff, remove it now and test flow again.

3. Flush the line with the showerhead off to clear trapped air

  • Turn off the showerhead (unscrew or close the head if it has a shutoff). If you remove the head, place a towel or bucket to catch water.
  • Open the shower valve(s) fully (hot and cold) and let water run for 1–2 minutes to force any air out. You’ll hear sputtering as air exits; keep the water running until it’s steady.
  • Replace or turn the showerhead back on and check pressure. If flow is still weak, repeat the flush a second time.

4. Check for debris or mineral buildup in the showerhead

  • If pressure improves with the head removed, the head might be clogged. Soak it in a vinegar solution or clean the screen and nozzles, then retest.
  • If removing the head makes no difference, the restriction is upstream (valve, cap, or supply line).

What Not to Do

  • Do not leave winter valves partially closed or caps in place — that will keep pressure low.
  • Do not force frozen valves open. If a valve is frozen or you feel it won’t move, stop and get professional help.
  • If you’re unsure what’s open or you can’t locate the shutoff, a plumber is appropriate — don’t guess and risk damaging the system.

When to Call a Professional

  • There’s no improvement after you confirm valves, remove caps, and flush the line.
  • You find a leak, wet insulation, a bulging section of pipe, or a valve that appears frozen or broken.
  • You can’t locate the correct shutoff or you’re uncomfortable working on the plumbing.

Safety Notes

  • When flushing, watch for sudden bursts of hot water that could cause scalding — start with cooler water if possible, and protect skin.
  • If antifreeze was used during winterization, flush thoroughly until there is no taste or odor and be careful about disposal; consult a professional if you’re unsure.
  • Do not apply excessive force to valves or fittings; broken parts can cause leaks and water damage.

Common Homeowner Questions

  • Why does it sputter even after I opened everything?
    Air pockets often take a minute or two of continuous flushing to clear; repeat the flush and run water steadily.
  • Can I remove the showerhead while the water is on?
    Yes — but point the spray into a bucket or drain and wear eye protection to avoid splashes.
  • What if the whole house has low pressure after winterization?
    That suggests a main supply issue or a partially closed main shutoff; call a plumber if you can’t restore full flow after checking main valves.

More posts