How to choose pipe for potable water distribution: multi-layer vs. copper vs. plastic

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How to choose a pipe for potable water distribution: multilayer vs. copper vs. plastic

Choosing the right pipe for potable water distribution is one of those decisions where it pays to stop and think it through from the very beginning. It's not just about the price per meter. It's about what will work worry-free behind the drywall or in the wall groove for the next thirty years – or, on the contrary, what will cause your bathroom to flood and require the entire distribution system to be replaced in five years. I've seen both.

Today's market offers three basic material groups: multilayer pipes (composite, with an aluminum core), copper pipes (straight rods or so-called soft coils like HEPWORTH), and plastic pipes (PP, PEX, PVDF). Each group has its place, its advantages and limitations. The goal of this article is to give you a sufficiently detailed picture so that you can make the decision yourself – or at least be able to have an intelligent conversation with the plumber.

Why the material matters more than most people think

A potable water distribution system is not just "a pipe for water." It is a system that must meet several demanding requirements at once. It must be hygienically safe – that is, it must not release substances into the water that would be harmful to health. It must be pressure-resistant and thermally resistant – after all, hot utility water circulates at 55–65 °C, and at an unfortunate boiler setting, even higher for a short time. It must withstand mechanical stress – expansion due to temperature changes, vibrations from pumps, and possible water hammer in the pipe. And finally, it must be installable under the specific conditions of your construction.

Hygiene and material safety are a separate chapter, which we will address in more detail in the article Hygiene and material safety of potable water pipes: what you need to know. Here we will focus on the practical comparison of materials in terms of installation, durability, price, and suitability for different situations.

Multilayer pipe: a composite that has won plumbers over

Multilayer pipe (in English composite pipe or multilayer pipe) is today probably the most widespread material for new single-family homes and renovations of apartments in Slovakia. And that for good reasons.

It typically consists of five layers: an inner layer of PE-RT or PE-Xb (in contact with water), an adhesive layer, an aluminum core (welded solid or corrugated), another adhesive layer, and an outer PE sheath. The aluminum core is key – it reduces oxygen diffusion (important for heating), dramatically reduces thermal expansion (close to that of metal), and gives the pipe shape memory: it bends and holds the shape.

Dimensions and parameters of multilayer pipes

In practice, the following dimensions are most commonly used for household potable water distribution:

16 × 2 mm – the smallest common dimension, ideal for individual outlets (basin, shower, bidet). Inner diameter 12 mm.
18 × 2 mm – a compromise dimension, suitable for shorter sections or groups of outlets.
20 × 2 mm – the basic supply dimension, suitable for connecting branches and main lines in an apartment.
25 × 2.5 mm and larger – for horizontal main lines in a house, or in the case of a large number of outlets.

On atria.sk, for example, you can find multilayer pipe IVAR TURATEC 16 × 2 mm in a coil of 200 m, which is certified for potable water and achieves PN10 classes at temperatures of +70 °C and +95 °C. For a thicker distribution line, multilayer pipe 20 × 2 mm in a coil of 100 m is available, or 18 × 2 mm in a coil of 200 m. For larger orders (entire house, apartment core), it pays to buy coils – the price per meter drops and waste is minimal.

What do the parameters PN10 and temperatures +70 °C / +95 °C mean?

The abbreviation PN (Pressure Nominal) indicates the nominal pressure in bars that the pipe can withstand at a reference water temperature of 20 °C. PN10 therefore means 10 bar. This is more than sufficient reserve for a typical household distribution system with municipal pressure of 3–6 bar. More interesting is the dual temperature classification: the same pipe can operate at 70 °C long-term (hot water circulation, seasonal operation) and at 95 °C short-term (protection against thermal shock). More on this topic can be found in the article Pressure classes PN10 and temperatures +70 °C vs. +95 °C: what they mean for your distribution system.

Advantages of multilayer pipe in practice

Shape memory – it bends manually or with a bender without fittings in curves. The real savings in fittings in the distribution is significant.
Low thermal expansion – compared to PP, it is about 4× lower, so expansion compensation is simpler.
Compact installation – thin wall (typically 2 mm) means a large inner diameter at a small outer dimension.
Simple installation with compression fittings – does not require open flame, no smoke is produced, even an experienced layperson can manage it (although we recommend a professional).
Resistance to corrosion – plastic surfaces are not prone to corrosion, the aluminum is protected inside.

Limitations of multilayer pipe

Requires precise compression – a poorly inserted fitting or incorrectly compressed joint will cause a leak.
The aluminum core is susceptible to galvanic corrosion when in direct contact with another metal (e.g. copper) without the correct transition fitting.
Visible distribution is not the most aesthetically pleasing – it is usually laid under plaster or in channels.
Bending with too small a radius can cause the aluminum core to crack – the minimum bending radius must be observed according to the dimension (for 16 × 2 mm typically min. 5× outer diameter = 80 mm).

Copper pipes: a classic with good reason

Copper has been used in plumbing for hundreds of years and still dominates in many countries (UK, Germany, Switzerland, Austria) for potable water distribution. It has properties that no plastic can fully replace.

HEPWORTH – soft copper pipe on reels

The term HEPWORTH is used in practice as a trade name for soft copper pipe supplied on reels (in contrast to hard copper rods). It is a full copper pipe made from food-grade certified copper Cu-DHP, but since it is annealed, it can be bent manually or with a bender – similar to multilayer pipe.

On atria.sk you can find HEPWORTH 15 mm pipe on 50 m reel and HEPWORTH 22 mm pipe on 50 m reel. The 15 mm dimension corresponds to a typical outlet line (equivalent to 1/2"), while 22 mm is a common supply size for bathrooms and kitchens (equivalent to 3/4").

Properties of copper pipe

Copper has several exceptional properties:

Natural antibacterial effects – copper inhibits the growth of bacteria including Legionella pneumophila. This is important especially in hot water circulation systems or in long stagnant sections.
Thermal resistance – copper can operate without problems at 95 °C long-term, and also with steam or hot water at higher temperatures. It has no competition in this regard.
Stiffness and mechanical strength – copper pipes are stiffer, more resistant to mechanical damage, and better able to withstand shock loads.
Recyclability – copper is 100% recyclable without loss of properties. From an environmental perspective, copper is very favorable in terms of long-term life cycle.
Long service life – a properly installed copper system can function for 50–70 years. No living plumber has yet seen a copper pipe that has reached the end of its service life.

Disadvantages and limitations of copper pipe

Higher price – copper is a commodity metal with a world price that fluctuates. Compared to multilayer pipe, the price per meter is higher, sometimes even 2–3×.
Installation requirements – soldering (soft soldering) requires experience, proper flux and an open flame. A faulty joint can show up immediately or after years. An alternative is crimping with crimp fittings, but this requires special crimping tools for copper.
Corrosion in aggressive water – water with low pH (below 7.0) or high chloride content can cause corrosion of copper pipe. In Slovakia, water quality is generally favorable, but in some regions (well water supply, mountainous areas) it is necessary to check the water chemistry.
Condensation on cold pipes – cold water in a warm environment causes condensation on the outside of copper pipes. Insulation is required.
Galvanic corrosion – direct connection of copper and steel pipe without a dielectric fitting causes galvanic corrosion. This must be considered in combined pipe systems.

A more detailed installation procedure for copper pipe can be found in the article Installation of HEPWORTH copper pipe: soldering or crimping.

Plastic pipes: PP, PEX and others

Under the term "plastic pipe" there are several different materials with quite different properties. It is important to distinguish between them, as the layman's idea of a "plastic pipe" includes both very high-quality materials and less suitable solutions.

Polypropylene (PP-R, PP-H)

PP-R (polypropylene random copolymer) is a common material for hot and cold water distribution. It is installed using fusion welding – with a special welding tool with Teflon inserts. The joint is strong and, when properly done, practically reliable for the entire lifetime. However, the high thermal expansion is a drawback – in hot water distribution, the pipe can expand by 10–15 mm per meter when heated from 20 to 60 °C. This requires expansion loops or compensators, otherwise the pipe may crack or detach from the wall. Another drawback is the thicker wall – with an outer diameter of 20 mm, the inner diameter is only 13.2 mm (wall thickness 3.4 mm), which is less than in multilayer pipe 20 × 2 mm (inner diameter 16 mm).

Cross-linked polyethylene (PEX)

PEX (cross-linked polyethylene) exists in three variants according to the manufacturing process: PEX-a, PEX-b, PEX-c. It has better heat resistance than PP, high flexibility and good resistance to pressure shocks. It is installed using crimp or clamp fittings. Pure PEX (without an aluminum insert) has, however, a problem with oxygen diffusion – air passes through the pipe wall, which is a problem in heating (boiler and radiator corrosion), less significant in potable water. Another issue is that PEX does not retain its shape after bending – fittings or spring supports are needed in every bend.

When to choose plastic and when not to

Pure plastic piping (PP or PEX without an aluminum insert) is suitable for:

Visible pipe runs, where the lightness and aesthetics of white PP are appreciated.
Extensive pipe runs, where low material cost is a priority.
Applications where expansion is not an issue (cold water, short sections, free laying).

On the contrary, pure plastic piping is not recommended for:

Circulation pipe runs of hot water embedded in the structure (expansion will cause cracking and separation).
Applications with frequent temperature shocks (boiler with electric after-heating, solar collectors).
Systems where the customer desires long-term warranty certainty without repairs.

Direct comparison: table of key properties

Property	Multilayer (PE-Al-PE)	Copper (HEPWORTH)	PP-R (plastic)
Max. temperature (long-term)	95 °C (PN10)	>100 °C	60–70 °C (PN10)
Max. operating pressure	10 bar (20 °C)	15–20 bar	10–16 bar
Thermal expansion	Low (2.6 × 10⁻⁵/°C)	Very low (1.7 × 10⁻⁵/°C)	High (~15 × 10⁻⁵/°C)
Flexibility	Excellent, retains shape	Good (soft Cu)	Low (rigid)
Installation	Crimping fittings	Soldering / crimping	Welding (hot tool)
Corrosion resistance	Excellent	Good (pH 7+)	Excellent
Antibacterial properties	No	Yes (Cu ions)	No
Price per meter (approximate)	Medium	Higher	Lower
Lifespan	30–50 years	50–70+ years	25–40 years

Which material for which situation? Practical scenarios

Scenario 1: Apartment renovation – pipes behind drywall

This is a classic case. An apartment in a panel building, you are renovating the bathroom, and the pipes will run behind a new drywall partition or under a new floor. What do we recommend? Multilayer piping. Reasons: easy installation without open flame (no fire hazard or insulation damage), shape memory allows routing without unnecessary fittings, low expansion prevents cracking when heated, and in case of a leak (faulty installation), it can be repaired with a related crimp fitting without replacing the entire section. Dimension 16 × 2 mm for individual branch lines, 20 × 2 mm for the supply to the bathroom from the main vertical pipe.

Scenario 2: Single-family house – complete house piping from the inlet to the outlets

New construction of a single-family house with underfloor heating, 3 bathrooms, kitchen. Here it pays to consider a combination: main inlet from the water meter to the manifolds – multilayer 20 mm or 25 mm (or copper 22 mm, if you want longer lifespan). Branches to individual outlets – multilayer 16 mm. If the house is in an area with good water quality and the investor wants to invest in quality, copper piping provides long-term satisfaction and antibacterial protection. The material cost will be higher, but with a 50-year lifespan, the total cost ends up being similar.

Scenario 3: Garden house or seasonal buildings

The situation is different here – the piping must withstand seasonal disconnection and possible freezing of water in the pipes. PEX or soft copper piping can better withstand occasional freezing than rigid PP (pressure wave from ice expansion cracks PP, PEX and copper expand better). Multilayer piping can also withstand one freeze, but repeated freezing may damage the aluminum core.

Scenario 4: Renovation of an old installation made of galvanized steel

Old apartment cores, panel buildings from the 70s and 80s – galvanized steel piping. During renovation, it is practically always replaced with one of the modern solutions. Be careful with galvanic corrosion when connecting new piping to the old steel remnants: copper piping connected directly to steel without a dielectric fitting will accelerate corrosion of the steel section. Multilayer piping is less problematic in this respect, but even with it, the correct transition fittings must be used.

Dimensioning: which pipe diameters do you really need

Correct pipe sizing is key to comfortable water flow. A pipe that is too thin will cause pressure and flow to drop significantly when multiple outlets are used simultaneously (shower + sink + WC). A pipe that is too thick is unnecessarily expensive and in long sections of cold water, stagnation and microbial deposits are a risk. A detailed methodology can be found in the article What pipe diameter do I need for domestic water supply and in Pipe sizing for drinking water: how to calculate diameter and length. Here we provide practical recommendations:

Single outlet (sink, bidet, WC cistern, shower): 16 × 2 mm multilayer or Cu 15 mm
Group branch (2–3 outlets in the bathroom): 20 × 2 mm multilayer or Cu 22 mm
Horizontal distribution per floor (up to 4 bathrooms/kitchen): 20–25 mm multilayer or Cu 22 mm
Main supply from the water meter / riser (whole house, apartment building): 25–32 mm or Cu 28 mm

Installation: when to do it yourself and when to call a plumber

Multilayer pipe with compression fittings may seem like "installation for everyone". Technically, this is true – the principle is simple: insert the pipe fully into the fitting and compress it with a compression plier. However, practice shows that the most common errors are:

The pipe is not inserted fully to the stop – the joint may leak under pressure or after a few months.
The end of the pipe is not properly calibrated after cutting (cutting tools deform the diameter) – the joint does not seal.
Compression was performed with the wrong jaw profile (each manufacturer of fittings has its own compression profile – U, B, TH…).
The pipe is not supported at sufficient intervals, causing stress and strain on joints and connections due to the position of the pipe.

A detailed step-by-step installation procedure including the necessary tools can be found in the article Installation of multilayer pipe step by step: tools, procedure, errors. Soldering copper pipe is recommended to be left to professionals or at least to complete practical training – a poorly soldered joint may fail even after years, when the pipe is already embedded and repairs are costly.

Hygienic safety: what to consider when choosing

Every material coming into contact with drinking water must meet European standards – primarily EN 1422, EN ISO 15874 (PP), EN ISO 15875 (PEX), EN 1057 (copper), and related hygienic certificates. In Slovakia, technical conditions of the Ministry of Health also apply. Practically, this means: buy only materials with proven certification for drinking water (the label or technical sheet should explicitly state "drinking water" or "potable water"). Do not buy unbranded products from hardware stores without documentation.

Another aspect: water stagnation. In long dead-end sections (long supply to rarely used outlets), bacterial growth is a risk in plastic pipes at temperatures of 25–50 °C. Copper pipe mitigates this problem. In multilayer and plastic pipes, solve it by circulation, shortening dead-end sections, or regular flushing.

Detailed comparison of multilayer and copper HEPWORTH

Since these two types are the most common choice in practice for new drinking water supply systems, we give them special attention. A broader view is also provided in a separate article Multilayer pipe vs. HEPWORTH: which is better for your system – here we summarize the most important points.

From the perspective of long-term reliability, copper is slightly better – its history is centuries long and countless copper systems have been operating without repairs for 60+ years. Multilayer pipe has a shorter history (it became widespread in the 90s), but test data predict a lifespan of 50+ years with proper installation.

From the perspective of practical installation, multilayer pipe is better – it does not require open flame, is more tolerant to common installation errors (to a certain extent), and is clearly preferred in densely populated areas (where a torch poses a risk of fire to insulation or wood).

From the perspective of hydraulic losses, copper is better – a smoother inner surface and a larger internal diameter for the same outer size reduce hydraulic resistance. In practice, this is not decisive for a typical home system, but it is noticeable in long sections and higher flows.

Common mistakes in the selection and installation of drinking water pipes

Over the years of practice, we keep seeing the same mistakes. We list them so you can avoid them:

Too small diameter on the main supply – in a new build, the plumber saves on the main pipe (e.g. 16 mm instead of 20–25 mm) and the customer has a pressure problem for the rest of the system's life when multiple outlets are used simultaneously.
Mixing materials without transition fittings – copper pipe directly on steel, or multilayer pipe on old copper without a dielectric fitting.
Burying without pressure testing – the system is buried and after months a wet stain appears. A pressure test (at least 1.5× working pressure for 30 minutes) is mandatory before covering the pipes.
Ignoring expansion in PP pipes – a hot water PP system without expansion loops bends and breaks wall fixings after the first heating.
Uncalibrated cut of multilayer pipe – a deformed end of the pipe from a cutter does not fit properly into the fitting and the joint does not seal.
Not insulating cold water pipes in warm areas – condensation damages the surrounding structure and increases cooling energy losses of the water.

Read more about typical faults and their causes in the article Common faults and leaks in drinking water pipes: causes and solutions.

Most frequently asked questions (FAQ)

Can I combine multilayer and copper pipe in one system?

Yes, the combination is common and functional, but you must use the correct transition fittings designed for copper–multilayer transition. Without them, galvanic corrosion is a risk at the contact point. A typical example is copper riser pipe in an apartment building and multilayer horizontal distribution in the apartment. You also need to pay attention to the direction of water flow: copper → multilayer is acceptable, but multilayer → copper with hot water may release microscopic aluminum ions into the water, which is not ideal.

Is multilayer pipe safe for drinking water?

Yes, provided it is a product with certification for drinking water (e.g. KTW, WRAS, ACS or their equivalents). The inner layer of PE-RT or PE-Xb is inert, does not release any harmful substances into the water, and plasticizers or other additives are not used in polyethylene. The aluminum core is not in contact with water, so there is no risk of aluminum release.

What is the difference between soft HEPWORTH and rigid copper pipe in rods?

Soft (annealed) copper pipe – HEPWORTH – is supplied in coils, can be bent manually or with a bender, which saves on fittings. Rigid copper pipe in rods (3 m) is stiff and cannot be bent – each direction of the route requires a fitting (elbow, T-joint). Soft pipe is more suitable for renovations and complex routes, rigid pipe for straight long runs in industry or technical rooms.

Which pipe better withstands freezing?

Soft copper pipe and PEX withstand single freezing relatively well – they expand and return to their original shape after thawing. PP pipe cracks when frozen. Multilayer pipe can withstand one freeze, but repeated freezing may damage the aluminum core, causing a leak. For seasonal buildings with a risk of freezing, we always recommend complete system drainage or PEX pipe with sufficient pipe insulation.

How much does a drinking water system cost in a typical apartment and where is it worth saving?

In an apartment with two bathrooms and a kitchen, the cost of the water system material (pipe + fittings + fastening) ranges from 150 to 400 € depending on the material and dimensions. The plumber's labor is usually several times higher than the material cost. Therefore, do not save on the quality of the pipe and fittings – the difference between cheap and quality material is just a few tens of euros, but repairing a leak behind drywall costs hundreds. You can save on route optimization (shorter pipe = less material) and by doing simple tasks yourself (helping with trench digging, installing fastening clips).

How long will the IVAR TURATEC multilayer pipe last?

The multilayer pipe IVAR TURATEC is designed for a service life of 50 years under correct operating conditions (temperature up to 70 °C at PN10, or short-term up to 95 °C). This is in line with European standards for multilayer pipes (EN ISO 21003). The key condition for long service life is correct installation of fittings, compliance with the minimum bend radius, and protection against UV radiation in outdoor installation.

Conclusion: how to make the right decision

Selecting a pipe for the distribution of potable water is not a decision where there is one clearly correct and all other incorrect materials. Each of the three basic types – multilayer, copper, and plastic – has its justified use in specific conditions.

If you are renovating an apartment or building a new family home and are looking for the best ratio of price, ease of installation, and reliability: multilayer pipe is today the standard recommended option. Use IVAR TURATEC 16 × 2 mm for branch lines and IVAR TURATEC 20 × 2 mm for group and main lines. If maximum long-term reliability, antibacterial properties, and no compromises are your priority: copper pipe HEPWORTH – for example HEPWORTH 15 mm for branch lines – is an investment that will pay off in decades of trouble-free operation.

Pure plastic PP pipe is suitable for visible piping or where cost is the primary factor and installation conditions allow – mainly for cold water and shorter-term applications. When deciding on pipe sizes and specific routing, review other topics in our Knowledge Centre – from sizing, through installation procedures, to common customer questions in the article Frequently asked questions about potable water piping.

Do you have a question about this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.