common mistakes in flanging that cause leaks
Crushing is a process that achieves a permanent and reliable seal of the joints, but even the smallest mistake in the procedure can lead to costly leaks. Experienced installers know that 90% of problems arise not due to the quality of the material, but due to human error during the actual installation.
Improper pipe surface preparation
The most common cause of leaks is insufficient cleaning of the PEX pipe ends before fitting installation. If scratches or dirt remain on the plastic layer, the crushing ring will not make even contact with the metal, creating a microscopic gap.
Technical standards require the pipe end to be perfectly flat and free of any damage that could disrupt the contact between the crushing ring and the fitting body.
Interchange of crushing rings and incorrect tools
Each brand uses a different chemical composition of steel for crushing rings, so you cannot interchange rings between different manufacturers or pipe types. Using an incorrect crushing tool or setting an incorrect deep crushing depth will result in the ring either not compressing sufficiently or the pipe cracking.
- Using a Rehau ring on a Wavin fitting will immediately cause a loss of seal under pressure.
- Setting the crimper to a smaller diameter than 17 mm will not ensure the required pressure for deformation.
- Using an old, worn-out crimping tool will lead to uneven compression of the edge.
For the proper function of the system, always verify compatibility with products such as Elbow PRESS 90° - for PEX pipe - 17x17, where manufacturing tolerance is critical.
Error in insertion depth measurement
When the pipe is inserted into the fitting, it must reach the exact stop point, which is often marked on the body or measured according to a table. If the pipe is inserted too deeply, it may hit the internal disc and prevent sealing, or conversely, if it is inserted only partially, the crimping ring will crimp an empty space.
Practice shows that installers often ignore measurement and rely on feeling, which with T-piece systems such as T-piece PRESS - for PEX pipe - 17x1/2"Fx17 leads to inevitable leaks during the first water filling.
Incomplete deformation of the crimping ring
The crimping ring must be deformed so that it surrounds the pipe over the entire circumference, with the formation of two precise grooves. If the tool does not complete the cycle or the battery is only partially charged, the deformation will be inaccurate and the seal will lose its integrity.
Unlike threaded connections, where you can seal with tape, here the rule applies: if the ring does not reach the final position, the joint is non-functional and the entire piece must be replaced.
Exceeding the temperature limit during installation
When working in extreme conditions, for example in winter, the PEX pipe may be too cold and brittle, increasing the risk of micro-cracks during insertion. On the other hand, if crimping is done in a hot environment without control, the material may behave differently and the crimping depth may change.
It is recommended to store fittings and pipes in a room with room temperature for at least 24 hours before installation to ensure their optimal elasticity and strength during crimping.
Incorrect storage and handling of joints
Connections are sensitive to mechanical impacts, which can damage the crimping rings even before installation. If the fitting Insert PRESS - for PEX pipe - 17x17 is damaged during transport, the crimping process may not work properly and leaks will occur.
- Store fittings in a dry environment where they are not exposed to moisture and corrosion.
- Do not rely on visual inspection; always check the condition of the crimping ring with a magnifying glass.
- Do not reuse fittings for multiple installations, as the metal has already lost its properties.
Exceeding the maximum crimp depth and its consequences
One of the most common, yet rarely documented errors is "over-crimping," which occurs when the installer incorrectly sets the depth of the crimping tool or uses an incorrect size of the jaw. The crimping ring deforms beyond the designed limits, leading to the rupture of the internal sealing (if the fitting contains one) or excessive compression of the PEX pipe's plastic core.
Whenever the maximum allowable deformation depth is exceeded, the metal ring loses its flexibility and is no longer able to compensate for the system's thermal expansion. This means that even during the first heating of the water, a crack in the joint gap may occur. In such a case, it is not possible to achieve a seal by adjustment; the entire construction must be replaced.
Visual inspection of correct deformation
The correctness of crimping cannot be verified by measuring only the outer diameter, as deformation also occurs inside the joint. The key indicator is the shape of the ring surface after the process is completed. A properly crimped ring should have a smooth, even surface without visible folds or "bumps." If you see noticeable protrusions on the ring, it is a sign of incomplete compression or incorrect pipe placement before crimping.
Ignoring the material's temperature condition before installation
Materials such as PEX (cross-linked polyethylene) are sensitive to ambient temperature. At low temperatures (below +5 °C), the plastic pipe behaves brittlely and during insertion into the fitting, a microscopic crack may occur, which will manifest as a leak during subsequent crimping. Conversely, at extremely high temperatures, the material may soften too much and during crimping, a solid mechanical connection will not be formed.
Installers often underestimate this factor and work in inaccessible rooms or outdoors without any material heating. We recommend always storing pipes and fittings in the working room for at least 24 hours before starting work, so they reach equilibrium temperature with the surrounding environment.
Insufficient quality control of compression rings
Compression rings are made of high-quality steel, but even this steel is not immune to corrosion or mechanical damage during transport. If the ring is damaged (e.g., cut edges or scratches), the compression will be non-functional. The ring may not close into its final position, causing the compression tool to stop the process prematurely, yet the system will still be leaky.
It is essential to perform a visual inspection of each ring before installation. If you notice any anomaly on the ring's surface, immediately discard it and use a new piece. Using a damaged ring is a risk that is never worth taking.
| Error | Cause | Consequence |
|---|---|---|
| Surface dirt | Scratches, oil, dust | Microscopic gaps, leakage |
| Incorrect insertion depth | Pipe not inserted fully to the stop | Compression of empty space, leakage |
| Over-compression | Tool set too deep | Loss of elasticity, cracking |
| Combination of brands | Different chemical composition of steel | Immediate loss of tightness |
Visual inspection of ring deformation
Checking the final shape of the compression ring is critical, as it is the only visual confirmation of a correct mechanical connection. A properly formed compression should have a smooth surface without visible folds, which indicate incomplete deformation or incorrect pipe positioning before compression.
Frequently asked questions
Can I fix a leaking compression joint without replacement?
No, if the joint is leaking, you must completely redo it with a new piece, as the compression ring has already deformed and its original shape accuracy cannot be restored.
How long should I wait after compression before turning on the water?
Tightness is immediate, but we recommend testing the system only after the pipe has fully cooled down or heated up, in the case of hot water systems, to avoid thermal deformations.
Is it possible to use a universal compression tool for all brands?
Yes, there are universal tools, but they must be calibrated for specific sizes and brands; otherwise, incorrect deformation of the ring and subsequent leakage may occur.
Following these simple rules during installation and carefully checking each step will save you time and money on repairs caused by leaks in the heating system.
Do you have a question about this topic?
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