Common faults and leaks in drinking water pipes: causes and solutions

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Common pipe faults and leaks in potable water supply: causes and solutions

No water distribution system lasts forever without maintenance and attention. Whether it's a new building, where incorrect installation becomes apparent after a few months, or an older house, where years of operation have left their mark on every joint – pipe faults are among the most common and at the same time most unpleasant problems that households encounter. A dripping pipe under the sink is not yet a catastrophe. A leak in a poured floor or behind the bathroom tiling, however, can cause damage worth thousands of euros before you even notice it.

In this article, we will look at where and why faults occur, how to detect them before they cause serious damage, and what to do about them – whether it's a do-it-yourself repair or a case for a professional. We will focus mainly on modern materials that are commonly used today: multi-layer pipes, copper pipes HEPWORTH and classic plastic pipe systems.

Why leaks occur – basic causes

A leak is never random. Behind every drop of water stands a specific cause that can be identified and eliminated. From practice, it follows that the vast majority of faults fall into one of the following categories:

1. Installation errors

Installation errors are by far the most common cause of leaks – an estimated 60 to 70 % of all faults in new installations have their roots precisely here. Typical installation errors include:

Insufficiently crimped connection – with multi-layer pipes, it is true that if the crimping tool does not reach the correct position, the connection may look fine at first glance, but under pressure or thermal expansion, it will loosen. This usually becomes apparent only after the first cycle of heating and cooling.
Uncleaned or deformed pipe end – every cut must be perpendicular and without burrs. A skewed cut on a copper pipe prevents even crimping or compression and the result is a leak precisely at the joint.
Missing or incorrectly placed sealing – with threaded connections with an O-ring, it is enough for the sealing to shift or not fall correctly into the groove during installation, and the result is continuous dripping.
Insufficiently tightened threaded connections – this applies in both directions: over-tightened mounting nut on a plastic thread can tear the thread, while too loose a nut does not seal.
Lack of expansion compensation – if the pipe is not secured with sufficient space for thermal expansion, mechanical stresses develop in the joints, which will eventually result in a leak.

2. Corrosion and material degradation

Corrosion is a long-term process that becomes apparent later – sometimes even after years. Copper corrodes slowly, but with aggressive water with a low pH (below 6.5), the process is significantly accelerated. Classic galvanized steel pipes (still common in panel buildings) suffer from pitting corrosion from the inside, which leads to a significant reduction in the cross-section and eventually to the pipe wall breaking. With plastic pipes, it is more about UV degradation (if exposed to sunlight) or the aging of sealing O-rings.

A special chapter is galvanic corrosion – if two different metals are directly connected (for example, copper and steel without a dielectric transition), an electrochemical cell is created, which significantly accelerates corrosion. We have seen cases where such a connection corroded the pipe through in 5 years.

3. Excessive pressure and water hammer

A domestic water supply is designed for a working pressure that usually ranges between 2 and 6 bar. If the pressure in the network fluctuates or permanently exceeds 6 bar, it stresses all connections, fittings and the pipe itself. Particularly dangerous is a hydraulic shock – a sudden increase in pressure caused by the rapid closing of a valve or fitting. In old installations without shock absorbers, hydraulic shock can immediately tear an already weakened connection or fitting.

4. Mechanical damage

Pipes in the floor or in the wall are sometimes damaged during later construction work – drilling, cutting or even excessive loading of the structure. Plastic pipes can crack even from freezing, if they are not protected in unheated areas.

Failures according to pipe material type

Multi-layer pipes (PEX-AL-PEX)

Multi-layer pipes are now the dominant choice for new buildings. They are flexible, light, and with a quality laminated aluminum layer, they withstand pressure and temperature well. Despite this, they have their specific weaknesses.

The most common failure is unclamping of the crimped joint. This happens when fittings of incorrect diameter are used, or when the crimping tool is not properly adjusted or maintained. For multi-layer pipe 16×2 mm, the minimum insertion depth into the fitting is usually 20 to 22 mm – if the pipe is inserted less than that, the crimp is insufficient and the joint will loosen under pressure or during expansion.

Another problem is cracking of the central aluminum layer due to too sharp a bend. Each manufacturer specifies a minimum bending radius (for a 16 mm pipe, it is usually five times the diameter, i.e., at least 80 mm). If the pipe is bent more sharply, the aluminum will tear, weakening the pipe and eventually leading to cracking.

At higher temperatures, the plastic in the pipe is also at risk of creep – gradual deformation under long-term load. Therefore, it is important to distinguish the classes: multi-layer pipe 20×2 mm IVAR TURATEC is certified for PN10 at +70 °C, or PN10 at +95 °C, making it suitable for hot water distribution. If you were to use a pipe certified only for a lower temperature on such a line, long-term deformation of the joints and leaks could occur.

Copper pipes HEPWORTH

Copper pipes belong to the proven solutions with a long service life – up to 50 years or more with proper installation and good quality water. Problems arise in several typical situations:

Pinhole corrosion – localized corrosion that creates microscopic holes in the pipe wall. It is caused by aggressive water with low pH, high chlorine content, or certain minerals. It manifests as a chronically damp area or dripping without visible damage to the joint.
Poor soldering work – when soldering copper pipe HEPWORTH 15 mm, the surface of the pipe and fitting must be thoroughly cleaned and fluxed before soldering. If dirt or oxides remain on the surface, the solder will not fill the joint evenly, resulting in a leaky spot – sometimes invisible at first glance.
Overheated joint – if the pipe is overheated beyond the optimal temperature (approximately 250–350 °C for soft soldering), the flux burns off and the solder does not melt evenly. The result is a brittle joint with impurity inclusions.
Electrochemical corrosion at transitions – especially at copper–steel or copper–zinc transitions.

Copper pipe HEPWORTH 22 mm is commonly used for main house distribution lines. At this size, any soldering error is more noticeable – a larger diameter means a larger volume, higher flow, and higher pressure in case of a leak.

Plastic pipes (PP, PVC, PE)

Classic plastic pipes are particularly prone to failures related to material aging and improper use. Polypropylene (PP) pipes are joined by heat fusion – if the welding temperature is incorrect or the welding time is insufficient, the joint is not integral. A typical error is too short heating time, after which the pipe is pushed onto the fitting without the material softening sufficiently – the joint looks solid but will split under pressure.

How to recognize a fault in a hidden pipe system

Sometimes a leak is obvious at first glance – a visible drop, a wet stain on the ceiling or wall. Other times the situation is more complicated, especially when the pipe is embedded in the floor or in the wall. In such cases, the following symptoms are valuable:

Unexplained increase in water consumption – if your meter increases by tens of percent without a change in habits, look for a hidden leak. Check the meter with all outlets closed: if the meter is still turning, water is escaping somewhere.
Moisture on walls or floors – dark stains, peeling plaster, swollen floorboards, or mold in corners indicate long-term moisture.
Pressure drop – if the pressure drops significantly at multiple outlets simultaneously, it may indicate a leak on the main line.
Noises in the wall – a faint hum or noise in the pipe with all outlets closed is a typical sign of flow through a leak.
Results of pressure tests – every new pipe system should be subjected to a pressure test after installation (usually 1.5 times the working pressure for 30 to 60 minutes). If the pressure drops during the test, there is a leak in the system.

Most common faults with specific types of connections

Press-fit connections

Press-fit connections are now the standard for multi-layer pipes. They are fast, reliable and do not require open flame. Despite this, we encounter recurring errors in practice. The most dangerous one is the so-called unpressed connection – if a technician accidentally skips a connection during pressing, it looks the same as the others, but it leaks. Responsible pipe fitting manufacturers address this issue with special control grooves or color indicators that change after proper pressing.

Another problem occurs when the same location is pressed multiple times. If a connection is pressed, opened and pressed again, the O-ring may be shifted or damaged, leading to a leak. A pressed connection may be used only once – after opening, a new fitting must be installed.

Screwed and compression connections

Screwed connections with compression rings or O-rings are particularly prone to loosening due to vibrations and temperature cycles. In domestic water heating systems, connections go through several heating and cooling cycles every day, which gradually loosen the screwed connections. Therefore, the professional practice of adding thread sealing (PTFE tape or sealing compound) to each screwed connection is justified – but only where the fitting manufacturer prescribes it.

Soldered connections of copper pipe

We have already highlighted the issue of soldering errors above. We will add only a practical observation: when inspecting a soldered connection, its quality can be reliably assessed by a simple visual test – a properly made connection has a visible, even ring of solder around the perimeter. If the solder forms droplets or is missing in some places, the connection is incomplete.

Failures depending on the age of the installation

An experienced plumber knows what to expect when entering a house and knows how old the installation is. The results of years of field experience give a fairly clear picture:

New installation (0–2 years): problems are almost exclusively installation errors. Leaks are usually detected immediately after the first heating and pressurization, or during the first pressure test. Press-fit connections and screwed connections on valves are particularly risky.
Installation 5–15 years old: the first signs of wear on seals begin to appear (especially on valves), or galvanic corrosion at incorrect material transitions. Most modern multi-layer and copper systems are still trouble-free at this age.
Installation over 20–30 years old: if it is original galvanized steel pipe, a complete replacement must be expected. Corrosion from the inside is common at this stage, and patches will not help. With old copper systems, it depends on water quality – some last 40–50 years, while others reliably break down after 20.

More on how to choose the right material for a new installation can be found in the article How to choose pipe for potable water distribution: multi-layer vs. copper vs. plastic, where the materials are compared also in terms of long-term durability and maintenance-free properties.

Solving faults – step-by-step what to do

Visible leak at a valve or connection

If the leak is visible and accessible, the procedure is relatively straightforward: shut off the water supply, drain the system (by opening a tap at a lower level), and proceed with the repair. For a screwed connection, it is often sufficient to replace the sealing and tighten the connection again. For a pressed connection, the entire connection must be disassembled and a new fitting installed. For a soldered copper connection, the location must be heated, the solder melted, the pipe removed, cleaned, fluxed, and soldered again.

Important warning: never use permanent sealing or sealing compounds to cover a poor-quality connection. This is only a temporary solution that does not prevent further deterioration, but only delays the repair – and usually complicates future work.

Hidden leak in the floor or wall

Locating a hidden leak is the most challenging step. Today, thermal cameras (temperature differences at hot water leaks are clearly visible), acoustic detectors or pressure tests in sections are used to find it. After localization, a cut into the structure must be made, the damaged section replaced, and the structure resealed – always after a pressure test of the identified section.

In the case of hidden potable water distribution in the floor – for example, five-layer pipes embedded in anhydrite – we recommend considering complete removal and replacement with modern multi-layer pipes in protective sleeves during reconstruction. A protective sleeve (flexible hose) will allow possible pipe replacement in the future without demolition.

Repair of copper pipe with pinhole corrosion

Repairing a damaged location on a copper pipe due to pitting corrosion is not meaningful – if there is one location, others will appear in a few years. The correct solution is to assess the water quality (pH, hardness, chloride ions) and decide whether to replace the section or even the entire system with a material that is more resistant to the given water. Plastic or multi-layer pipes are significantly more resistant to aggressive water than copper.

Prevention of faults – how to avoid problems

Prevention is always cheaper than repair. This is doubly true for pipes, because repairs of hidden systems are not only expensive, but also constructionally demanding. A few proven rules:

Always perform a pressure test before covering – this is rule number one. Every new system before embedding or tiling must pass a pressure test. The recommended value is 1.5 times the working pressure, for 30–60 minutes. If the pressure drops by more than 0.1–0.2 bar, a leak must be found and repaired.
Correct material for the right conditions – the topic of material selection is discussed in detail in the article Multi-layer pipe vs. HEPWORTH: which is better for your system. Not every material is suitable for every application – a bathroom system behind tiling has different requirements than an outdoor supply or a technical room system.
Respect minimum bending radii – for multi-layer pipes, this usually means using a bending tool when forming larger arcs to avoid excessive compression of the pipe.
Proper support and compensation for expansion – pipes must be supported at prescribed intervals (for 16 mm multi-layer pipes, this is usually every 500–700 mm for horizontal runs) and must have space for thermal expansion. This is especially important for hot water – a 16 mm multi-layer pipe expands by about 5–6 mm per meter when heated from 10 to 70 °C.
Water quality check – in areas with aggressive or soft water, consider water analysis even before selecting the installation material.
Use of certified fittings and tools – each multi-layer pipe system has its own pressing system. Mixing fittings from different manufacturers can lead to leaks, as the dimensions of O-rings and gripping grooves are not always interchangeable.

The technical aspects of installation are discussed in detail in the article Installation of multilayer pipe step by step: tools, procedure, mistakes, where you will also find a detailed overview of common installation mistakes and how to avoid them.

When to fix it yourself and when to call a professional

Many homeowners hesitate whether to fix a problem themselves or call a plumber. The answer depends on the location, extent, and type of the problem:

You can fix it yourself: replacing the washer under a tap, sealing a threaded connection in an accessible location (e.g. under a sink), replacing a flexible hose connector to a faucet or toilet, repairing a dripping valve.

Call a professional: any problem in an embedded or inaccessible pipe, repairing a crimped or soldered connection, problems on the main supply pipe, situations where it is not clear exactly where the leak is, pressure problems throughout the house.

A special case is the reconstruction of pipe systems in panel buildings. Always verify ownership of the pipes and responsibility for their repair with the building manager or housing association – common risers are usually owned by the building management.

Pressure classes and their impact on reliability

The topic of pressure classes is discussed in detail in the article Pressure classes PN10 and temperatures +70 °C vs. +95 °C: what they mean for your system. Here we only remind you of the basic connection to problems: a pipe dimensioned for a lower pressure or temperature than the actual system parameters will gradually fail – first at the connections, later on the pipe itself. If you have a pressure above 4 bar in your house, we recommend using pipes with a reserve in the PN10 class, not PN6.

An interesting example from practice: in one new building, the hot water system was installed with pipes certified only for 70 °C, but the customer operated the tank at 80 °C for hygiene reasons (protection against legionella). After two years, leaks began to appear at the connections – long-term overheating caused softening of the plastic layers at the crimped fittings. The solution was to replace the pipes with ones certified for 95 °C.

System documentation – underestimated prevention

One of the most valuable things you can do after installing a new system is to create its documentation – photographically or schematically mark the pipe routes before they are covered. In practice, we repeatedly encounter cases where the owner after 10 years does not know where the system runs, and during drilling into the wall, the drill hits the pipe. Documentation is literally an investment that pays off once.

The ideal procedure is to photograph all pipe routes before pouring the floor and before plastering the walls, mark the positions of connections and valves on a simplified floor plan, and store this document together with the technical documentation of the house.

Most frequently asked questions (FAQ)

What to do if I find out that the water meter is moving even when all taps are closed?

The first step is to close the main water shut-off valve and record the state of the meter. If the meter stops after closing the main valve, the problem is before the meter – call the network manager or water utility. If the meter stops after closing the main valve, but moves when it is opened, you have a leak in your own system after the meter. The next step is to systematically close section valves (if you have them) and locate the section where the leak occurs. If you do not have section valves or the system is not accessible, contact a plumber with a thermal camera.

Can I use self-vulcanizing tape or epoxy sealant to repair a cracked pipe?

Yes, but only as a temporary emergency solution – for example, until the plumber arrives or until you obtain the material for the repair. No tape or sealant can replace a proper permanent repair. On pipes with drinking water, only materials certified for contact with drinking water are allowed. A permanent solution always means replacing the damaged section or connection.

Why is it still dripping after I repaired the connection, even though I replaced the gasket?

The most common causes are: an uneven or damaged seating surface (e.g. deformed metal at the valve), an unsuitable gasket (wrong material or size), insufficient tightening or over-tightening (broken thread), or the gasket slipped out of the groove during installation. Try replacing the gasket again, this time carefully checking the condition of the surfaces and the correct placement of the gasket before tightening.

How long does it take for a mistake in the installation of multilayer pipes to become apparent?

This depends on the type of mistake. An uncrimped connection or a completely omitted crimp will become apparent immediately upon the first pressurization. An insufficiently crimped connection (the jaw did not reach the correct position) may become apparent after the first or second temperature cycle – that is, after several days to weeks of operation. Therefore, a pressure test after installation is mandatory before covering, and also after a trial operation of the system for at least a few days before the final floor pouring.

What is the difference between a leak at the connection and a crack in the pipe itself?

A leaky connection is usually manifested by dripping or moisture precisely at the fitting or valve, while the pipe itself between the connections is dry. A crack or hole in the pipe creates a wet streak along the pipe or a leak point on its surface outside the connection. Cracks in pipes are less common and usually have a specific cause: freezing, excessive bending, mechanical impact, or significantly excessive pressure.

Is it necessary to replace the entire system if a leak appears at one point?

Not always. If the installation is relatively new (up to 15 years) and it is an isolated connection, only the damaged parts are repaired. If the installation is old, made of galvanized steel, or leaks appear at multiple points simultaneously, the more economical and lasting choice is to completely replace the system with modern piping. An old system at this stage is "beyond the limit" – every patch is only a temporary solution and the overall repair costs exceed the price of reconstruction. More about dimensioning a new system can be found in the article Dimensioning pipes for drinking water: how to calculate diameter and length.

Conclusion

Leaks and failures in drinking water pipes are common, but in most cases predictable and preventable. The key is quality material suitable for operating conditions, professional installation with attention to each connection, and pressure testing before covering. If a problem does occur, it is important to react in time – a hidden leak that is ignored causes much greater damage than one that is addressed immediately.

For new buildings or complex system reconstructions, we recommend looking at the range of multilayer pipes IVAR TURATEC – for example, the multilayer pipe 18×2 mm is suitable for most domestic drinking and hot utility water systems – and consider combining it with the proven copper piping HEPWORTH for sections where traditional material is preferred. The right combination of materials, professional installation, and thorough documentation are the foundation of a system that will last you trouble-free for many years.

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.