why my crimped joint is not sealing and how to fix it

Crimped joints are key components of modern heating systems, but even a minor mistake during pipe preparation or improper handling of the tool can lead to water leakage and subsequent damage. This article focuses on practical diagnostics of sealing issues in crimped joint systems and provides proven methods for their repair.

How to correctly identify a leaking crimped joint

The first sign of a problem is often a visible water droplet on the fitting body or a damp spot on the wall where the pipe is located, indicating a rupture of the sealing rubber. If the leak appears immediately after a pressure test, the cause is usually a mechanical error during installation, while a delayed leak may indicate material fatigue or corrosion.

Visual inspection should include a thorough analysis of the surface of the crimped ring, where the presence of oil stains or cracks immediately indicates a failed seal. Technicians often use the "dry cloth" method, running the entire circumference of the joint; if the cloth becomes wet immediately, it indicates a critical leak requiring immediate repair.

Causes of seal failure during installation

The most common cause of leakage is insufficient preparation of the pipe end, when a cutting mark or dirt remains on the PEX pipe, which disrupts contact with the sealing profile. Another frequent error is the use of an unsuitable crimping tool that does not achieve the specified pressure or has worn jaws, leading to inaccurate compression.

• Inadequate deburring of the pipe edge after cutting, causing a fold in the sealing rubber.
• Contamination of the internal space of the fitting with dirt or sand from the installation environment.
• Use of crimping pliers with an incorrect matrix size for the given fitting diameter.
• Failure to maintain the minimum compression time, leading to unstable shaping of the metal ring.

Step by step: Repair procedure for a leaking joint

Repair always begins by draining the water from the system and disconnecting the boiler's power supply to ensure safety when working under pressure. Next, it is necessary to remove the old crimping ring using a special cutter or grinding wheel, making sure not to damage the fitting body or the surrounding pipe.

After removing the old ring, it is necessary to check the condition of the sealing rubber inside the fitting; if it is damaged, the entire piece must be replaced, as repairing the seal alone is not possible. The pipe must be cut precisely again, cleaned of edges, and ensured to be fully inserted to the stop, which guarantees the correct position of the seal before new crimping.

Why is it necessary to replace the entire fitting?

In the case of more severe damage, such as a crack in the body of the brass elbow or deformation of the internal threaded profile, the only solution is to replace the entire piece. Attempts to repair such damage by gluing or soldering are extremely risky and not recommended under high temperatures and pressure in heating systems.

We recommend always using high-quality components such as Elbow PRESS 90° - for PEX pipe - 17x17, which have guaranteed durability and corrosion resistance. These fittings are designed to withstand long-term thermal stress without loss of sealing, which is crucial for the safety of the entire system.

Selection of replacement parts and materials

When replacing a leaking joint, it is critical to use the same type of fitting and the same crimping ring to maintain compatibility with the existing system. An incorrect type of ring, for example, made of a different material or with a different hardness, can cause either misalignment of the seal or its rupture during a pressure test.

For complex radiator connections, we recommend using T-piece PRESS - for PEX pipe - 17x1/2"Fx17, which allows safe and secure branching of the pipe without the need for additional threaded connections. Choosing the right material is the foundation for the long-term functionality of the system.

Prevention of future leaks and quality control

Prevention involves regular inspection and calibration of crimping pliers according to the manufacturer's instructions, which prevents under-crimping or excessive deformation of the rings. Regular testing of the entire system's tightness, including visual inspection and pressure testing, should be part of annual heating system maintenance.

• Regular inspection of crimping pliers and replacement of worn matrices.
• Thorough cleaning of the pipe before each new connection.
• Use of original crimping rings from the fitting manufacturer.
• Verification of the pipe insertion depth using a measuring tool before crimping.

Analysis of the crimped ring diameter measurement

Checking the final diameter of the compressed ring with a caliper is the only objective way to verify whether sufficient plastic deformation of the metal has occurred; if the measurement falls outside the tolerance, the joint is not safe, even if it does not leak.

Compression geometry and edge rounding

A regular shape of the compressed ring with a smooth rounding at the edges indicates a correct deformation process of the material, whereas sharp edges or irregularities indicate incorrect pliers positioning or damage to the fitting.

Frequently asked questions

Can I just tighten a leaking compressed joint?

No, a compressed joint cannot be tightened or repaired by additional compression, since the compression process is permanent and one-time. If the joint is leaking, you must completely reconnect it by replacing the ring and possibly the entire fitting.

What should I do if I used the wrong compression ring?

You must immediately drain the system, remove the old ring, and install the correct type of ring that matches the diameter and brand of the fitting. An incorrect ring will not provide sufficient sealing pressure and the system will leak.

How long will a repaired compressed joint last?

A repaired joint, if performed according to the technical instructions and using new parts, will last as long as the original joint, i.e., several decades. The key is a clean process and the use of quality materials, such as PRESS Insert - for PEX pipe - 17x17.

Correct diagnosis and thorough repair of a leaking compressed joint will allow you to keep your heating system running smoothly and avoid costly repairs in the future.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.