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How to Repair a Leaking Toilet Supply Line (Step by Step)

recently fixed toilet water supply line after leak

A leaking toilet supply line is a common plumbing issue that can cause water damage and increase your utility bills. Whether you’re a seasoned DIYer or a newbie, learning how to repair a leaking toilet supply line can save you time and money. 

In this step-by-step guide, we will show you everything you need to know to fix a toilet and restore functionality by repairing the leaking water supply line. We’ll also cover how to prevent the toilet supply line and water tank from leaking and why it’s happening. 

So, roll up your sleeves, and let’s dive into the world of plumbing repairs!

Reasons Why Your Toilet Supply Line Is Leaking

Toilet supply lines are prone to leaks due to various factors. Here are some common causes of toilet supply line leaks:

close up of toilet water supply line leak
  • Old or worn-out supply lines: Over time, supply lines can become worn out, leading to cracks, leaks, and other damage. 
  • Corrosion: Corrosion can occur due to exposure to chemicals in the water, leading to rust and other forms of damage.
  • Loose fittings: If the fittings connecting the supply line to the toilet tank or shut-off valve are loose, water can leak through the gaps, causing a leak.
  • High water pressure: When the water pressure is too high, it can cause the supply line to burst or leak.
  • Improper installation: If the fittings are not tightened properly, they can cause leaks.

How to Repair a Leaking Toilet Supply Line: Step-by-Step Guide

Here’s a step-by-step guide on how to repair a toilet water supply line leak:

Step 1: Turn off the Water Supply

The first step to fixing a leaking toilet supply line is to turn off the water supply. Locate the shutoff valve, usually found on the wall behind the toilet. Turn it clockwise until it stops.

Step 2: Drain the Water From the Toilet Tank and Bowl

Once the water supply valve is shut off, you should drain the water from the toilet tank and toilet bowl. To do this, simply flush the toilet a few times and hold down the handle until all the water has drained out.

Step 3: Disconnect the Supply Line From the Toilet Tank

Using an adjustable wrench or pliers, disconnect the supply line from the toilet tank by turning the nut counterclockwise until it comes loose. Be sure to have a bucket or towel handy to catch any remaining water that may come out.

Step 4: Inspect the Supply Line

Once the supply line is disconnected, inspect it for any damage or signs of wear and tear. Look for cracks, corrosion, or any visible leaks. If the supply line is damaged, it will need to be replaced.

If it has one small hole, some flex tape on the area can prevent leaking until you can afford a new line.

Step 5: Replace the Supply Line

If the whole line is damaged, you’ll need to replace it with a new one. Measure the length of the old supply line to ensure you purchase the correct replacement. 

Once you have the new supply line, connect it to the fill valve on the toilet tank by turning the nut clockwise until it’s hand-tight. Use pliers or an adjustable wrench to tighten it a bit further.

Step 6: Reconnect the Water Supply

plumber attaches toilet water supply line leak

Once the new supply line is in place, it’s time to reconnect the water supply. Turn the shut-off valve counterclockwise until it’s fully open, and allow the tank to fill up with water.

Step 7: Test for Leaks

Finally, turn the water supply back on and test for leaks by flushing the toilet a few times and inspecting the area around the valve and supply line for any water drops. If you notice any leaks, tighten the nuts a bit further until the leak stops.

Repairing a toilet water supply line leak is an easy fix that can save you time and money. By following these steps, you’ll have your toilet back up and running in no time! 

Remember to turn off the water supply before starting any repairs, inspect the supply line for any damage, and test for leaks before using the toilet again.

How To Prevent a Leaking Toilet Supply Line

A leaking toilet supply line can be a frustrating and potentially costly problem. Luckily, there are several ways to stop a leaking toilet supply line. Here are some steps you can take to prevent it:

  • Tighten fittings: Check the fittings connecting the supply line to the toilet tank and shut off the valve. If the fittings are loose, tighten them with a wrench until they are snug.
  • Replace washers: If the fittings are tight and the supply line is still leaking, the problem could be a worn-out washer. Turn off the water supply and remove the nut from the end of the supply line. Replace the old washer with a new one.
  • Replace supply line: Sometimes, your toilet supply line is poorly installed or just old. In such cases, tightening fittings and replacing washers won’t prevent a leaking line. Follow the steps above to replace the line.
  • Install a pressure regulator: If your home’s water pressure is too high, consider installing a pressure regulator. A pressure regulator can help regulate the water pressure and prevent leaks.

Preventing a toilet supply line from leaking water can be a simple DIY task. Start by checking and tightening the fittings and replacing the washer if necessary. 

If those steps don’t work, replacing the supply line or installing a pressure regulator can be effective solutions. By taking these steps, you can prevent water damage and save money on your utility bills.


Having your toilet supply line leaking can be a frustrating and potentially costly problem. However, by following the steps outlined in this article, you can quickly and easily repair the toilet water supply line leak and prevent further damage. 

Whether you need to tighten the fittings, replace a washer, install a new supply line, or adjust the water pressure, fixing the problem can save you money and protect your home from water damage. 

With these tips, you can confidently tackle any toilet supply line leak and keep your bathroom running smoothly.

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