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How to fix a toilet supply line leak

We'll tighten the connections or replace the supply line—and tell you when to call a plumber.

How-to · Home plumbing
10–20 min
What you'll need
  • Braided stainless supply line (12 or 20 inch, standard)
  • Two adjustable wrenches
  • Towels

At a glance

  • Shut off the water at the wall valve before working on the supply line.
  • Locate the leak—at the wall valve, at the fill valve, or along the hose.
  • Tighten the nuts a quarter turn with two wrenches; do not overtighten.
  • Replace a cracked, corroded, or bulging supply line with a new braided stainless line.
  • If the valve or fill valve connection will not seal, call a plumber.
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Steps

Goal: Shut off water, locate the leak, fix the connections or replace the line, and know when to call a plumber.

  • Shut off the water at the wall valve. Flush the toilet to drain the tank.
  • Good: No water flows. Proceed to Locate the leak.
  • Bad: Valve will not shut off—call a plumber.

Locate the leak

Goal: Identify where the water is escaping.

  • Dry the supply line, wall valve, and fill valve connection. Turn the water back on briefly. Watch where water appears.
  • Good: You see the leak source. Proceed to Tighten connections or Replace supply line based on location.
  • Bad: Cannot locate—call a plumber.

Tighten connections

Goal: Stop leaks at the wall valve or fill valve.

  • Shut off the water. Use two wrenches to tighten the supply line nuts a quarter turn. Do not overtighten. Turn the water on and test.
  • Good: No drips at either connection. Proceed to Verification.
  • Bad: Still leaks—replace the supply line or call a plumber.

Replace supply line

Goal: Fix leaks from a damaged supply line.

  • Shut off the water and flush to drain. Place a towel under the connections. Unscrew the nuts at both ends. Install a new braided supply line. Hand-tighten, then snug a quarter turn. Use the washers that come with the new line.
  • Good: No drips when the water is on. Proceed to Verification.
  • Bad: Connections will not seal—the fill valve or wall valve may be damaged. Call a plumber.

When to get help

Call a plumber if:

  • The wall valve will not shut off.
  • The fill valve connection is stripped or damaged.
  • You see water behind the wall.

Do not force fittings—you can damage the pipe. For other plumbing fixes, see Fix a toilet that runs or How to unclog a drain.

Verification

  • No drips at the wall valve or fill valve when the water is on.
  • The toilet tank refills normally after flushing.
  • No water on the floor around the toilet.

Reviewed by Blackbox Atlas

Frequently asked questions

Why does my toilet supply line leak?
Common causes: loose nuts at the wall valve or fill valve, a worn rubber washer, or a cracked or corroded supply line. Older plastic lines crack with age; braided stainless lines last longer.
Can I fix a toilet supply line leak myself?
Yes. Most supply line leaks are fixable by tightening the connections or replacing the line. Shut off the water at the wall first. If the valve or fill valve is damaged, call a plumber.
When should I call a plumber for a supply line leak?
Call a plumber if the wall valve will not shut off, the fill valve connection is stripped or damaged, or you see water behind the wall. Do not force fittings—you can damage the pipe.

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