A compression fitting is a common and essential component used in plumbing systems to connect two pipes or a pipe to a fixture. These fittings are widely favoured for their simplicity and effectiveness in forming watertight connections without the need for soldering. However, despite their reliability, they are not immune to leaks. Leaks in compression fittings can occur due to various reasons, such as wear and tear, improper installation, or material degradation. Recognising the signs of a leaking compression fitting and understanding its common causes are pivotal in addressing the issue efficiently.

Tee Compression Fitting

How Do Compression Fittings Work?

The mechanism behind a compression fitting is relatively straightforward. When the compression nut is tightened, it presses the olive against the pipe and the body of the fitting. This pressure deforms the olive slightly, causing it to grip the pipe tightly and create a watertight seal. The effectiveness of this seal depends on the correct installation and the condition of the fitting components. A typical compression fitting comprises several key components:

  1. The compression nut, which tightens onto the fitting.
  2. The olive, also known as a ferrule, which is a small ring made of brass or copper that gets compressed to create a seal.
  3. The body of the fitting, which houses the pipe or tube. Each component plays a vital role in ensuring a secure and leak-free connection. Understanding these parts is crucial for diagnosing and fixing any leaks that may occur.

Common Causes of Leaks in Compression Fittings

Leaks in compression fittings can arise from several issues:

  1. Improper Installation: If the fitting is not tightened correctly, it can lead to leaks. Over-tightening can also be problematic, as it may damage the olive or the pipe.
  2. Wear and Tear: Over time, the components of the fitting can wear out, especially if exposed to harsh conditions or high water pressure.
  3. Corrosion and Material Degradation: In some cases, the materials of the fitting can corrode or degrade, particularly in areas with hard water or aggressive chemicals.
  4. Movement and Stress: Pipes that are subject to movement or stress may cause the compression fitting to lose its seal over time.

Step-by-Step Guide to Fixing a Leaky Compression Joint

The significance of promptly addressing leaks in compression fittings cannot be overstated. Even minor leaks can lead to significant problems over time, including water damage to structures, increased water bills, and the potential for mould growth.

What You Need

  • Adjustable Spanner x 2
  • Replacement Olives (Ferrules)
  • PTFE Tape or Joint Compound (if necessary)
  • Cloth

Step 1 – Turn the Water Off

The foremost step in addressing a leaking compression fitting is ensuring safety. This involves turning off the water supply to the area where the fitting is located. Locate the nearest shut-off valve and turn it to the off position. If a local shut-off valve is not available, you may need to turn off the main water supply to the house.

Always confirm that the water is completely turned off by opening a tap near the work area to release any residual pressure in the pipes.

Step 2 – Identify the Source of the Leak

The first step in the repair process is to identify exactly where the leak is originating. Wipe the area dry with a cloth and observe closely. Look for water seeping from the connection between the pipe and the fitting. Sometimes, the source of the leak might be obvious, but in other cases, it might require close inspection.

Step 3 – Tighten the Compression Fitting

Often, a leak can be fixed simply by tightening the compression fitting. Use a pair of grips and an adjustable spanner for this task – the grips to hold the body of the fitting in place and the spanner to tighten the nut. Turn the nut clockwise, but be careful not to over-tighten, as this can damage the olive or the pipe. A good rule of thumb is to tighten it until it feels snug and then give it a quarter turn more.

Step 4 – Seal the Fitting

If tightening the fitting does not stop the leak, you might need to apply PTFE tape or a joint compound to the olive and the threads of the compression nut to ensure a watertight seal. Wrap the PTFE tape around the threads in the direction that tightens the nut (usually clockwise). If using a joint compound, apply it evenly on the threads before reassembling the fitting.

Step 5 – Replace Damaged Components

If the leak still remains, you may need to replace damaged components. Carefully remove the compression nut and slide it along the pipe, then remove the old olive. Replace it with a new olive of the correct size and reassemble the fitting. Make sure everything is aligned correctly before tightening.

Step 6 – Test for Leaks

Once the repair has been completed, it’s crucial to test for leaks to ensure the issue has been effectively resolved. Gradually turn the water supply back on to the area where the repair was made. Observe the compression fitting closely as the water pressure builds up. Allow the water to run for a few minutes and check for any signs of leakage. Pay attention to any drips or moisture around the fitting. It’s essential to do this cautiously to avoid sudden pressure surges that could exacerbate any potential leaks.

Troubleshooting Persistent Leaks

If, after your repair and testing, the leak persists, consider the following steps:

  1. Recheck the Tightness: Sometimes, a slight additional tightening can resolve the issue. However, be cautious not to overtighten.
  2. Inspect for Misalignment: Ensure that the pipe is correctly aligned with the fitting. Misalignment can cause uneven pressure and result in leaks.
  3. Examine for Pipe Damage: Check the pipe itself for any damage or wear, as this could be the cause of the leak rather than the fitting.
  4. Seek Professional Help: If you’ve retried the repair process and the leak continues, it might be time to call a professional plumber. Persistent leaks may indicate a more complex issue that requires expert intervention.


In this article, we’ve covered the essential steps to fix a leaking compression fitting and regular maintenance of your plumbing system is key to preventing future leaks and ensuring the longevity of your fittings and pipes. Periodically check your plumbing fittings, especially compression fittings, for any signs of wear, corrosion, or leaks. Early detection of potential issues can save time, money, and prevent the hassle of dealing with more severe water damage down the line. A proactive approach to plumbing maintenance is always more beneficial than a reactive one.

How to Fix a Leaking Compression Fitting Infographic
How to Fix a Leaking Compression Fitting Infographic

Plumbing Wizard Tips

“Always turn off the water supply before attempting any repair on a compression fitting to ensure safety and prevent further leakage!”

“Regularly check and replace worn-out olives or ferrules in the fitting, as these are often the culprits behind leaks!”

“If a leak persists after tightening, consider applying PTFE tape or joint compound to the threads for an extra seal!”

Frequently Asked Questions

How do I stop my compression fittings from leaking?

To stop a compression fitting from leaking, ensure it is properly aligned and tightened securely, but not over-tightened. If the fitting continues to leak, check and replace any damaged components, such as the olive or ferrule. The key is to ensure all parts are in good condition and properly assembled.

What is the most common cause of leaking compression fittings?

The most common cause of leaking compression fittings is improper installation, which can include misalignment, incorrect tightening, or the use of worn-out components. Over time, wear and tear or corrosion can also lead to leaks.

Should I put PTFE tape on compression fittings?

No, PTFE tape is not normally used on new compression fittings but if you find that the joint is still weeping after tightening, a couple of wraps of tape won’t hurt.

Do compression fittings need sealant?

Compression fittings do not typically require sealant but if the joint is still weeping after it has been tightened, a little compound will probably finish the seal.

Can you over tighten a compression fitting?

Yes, you can over tighten a compression fitting, which may damage the fitting or the pipe. Over-tightening can lead to deformation of the olive or ferrule, causing it to lose its ability to effectively seal, and potentially leading to leaks. It’s important to tighten the fitting just enough to create a seal without applying excessive force.


Lee Pearce is not just a master plumber; he’s a veritable Plumbing Wizard. With over 30 years of experience in the trenches of pipes and drains, Lee has become the go-to sage for DIY plumbing, saving homeowners thousands in potential call-out charges. As the founder of Plumbing Wizard, he’s dedicated to demystifying the complexities of home plumbing, offering easy-to-follow advice that stands the test of time and pressure. His online blog is a treasure trove of tips, tricks, and tutorials that empower everyday individuals to take charge of their home’s plumbing health. Lee’s practical wisdom is not just about fixing leaks; it’s about imparting confidence and self-reliance. When he’s not writing or elbow-deep in a plumbing project, Lee is passionate about educating the next generation of DIYers, ensuring that practical skills are passed down and preserved.

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