Pipes & water supply

Shutoff valve won't fully stop the water

A valve that still lets water through when closed usually has worn internal seals or a damaged seat, and this should be addressed before you rely on it during an emergency.

Difficulty
Moderate
Time
30–45 minutes
DIY cost
$10–$30
Pro cost
$120–$250

Symptoms

  • Water still trickles or flows past a valve that's fully closed
  • Valve turns smoothly with no resistance issues
  • Problem noticed only when trying to do a repair downstream
  • Valve is old or rarely operated

Likely causes

  • CommonWorn washer or seal inside the valveLike other faucet-type seals, the internal washer that blocks flow when closed can wear out over years.
  • CommonDebris lodged in the valve seat preventing a full sealSediment or mineral particles can sit right where the valve needs to close tightly, keeping it from sealing completely.
  • PossibleCorroded or damaged valve seatPhysical damage to the seat surface can prevent a full seal even with a good washer.
  • Less commonValve simply worn out and needing full replacementSome older valve types degrade to a point where individual part replacement isn't practical.

What to do

  1. Confirm the issue by fully closing the valve and checking if water still flows at a downstream fixture or opening.
  2. If it's a valve you can access easily (like an appliance or fixture stop), shut off water further upstream (like the main) to relieve pressure safely.
  3. Disassemble the valve to inspect the washer or seal for wear, replacing it if degraded.
  4. Check the seat for visible debris or damage, cleaning out any sediment you find.
  5. Reassemble and test again; a valve that still won't fully stop water after cleaning and reseating likely needs full replacement.
  6. For a valve you were relying on for an upcoming repair, replace it with a modern quarter-turn ball valve, which is more reliable long-term than older compression stops.
  7. Test the new valve fully closed and reopened several times before considering the repair complete.

Tools and parts

  • Adjustable wrench
  • Screwdriver
Quarter-turn ball valveSearch: “quarter turn shutoff valve replacement”

When to call a pro

Call a plumber if you need the main water shut off to safely replace a valve, or if the valve continues to fail after replacement.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.