Frequently asked questions about pipes for potable water distribution

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Common questions about potable water piping – answers from practice

Everyone who has ever dealt with the renovation of plumbing or the construction of a new building will sooner or later come across a heap of questions for which they are not sure of the answer. Which material to choose? What diameter is correct? What does PN10 mean? Can multilayer piping be bent around a corner without fittings? Can the same pipe be used for cold and hot water? These questions are not trivial – a wrong choice may only become apparent after several years, when the pipe is already embedded in the wall and the repair will cost several times more than the whole material cost.

This article collects the most frequently asked questions that our customers ask – by phone, by email, or directly at the store. The answers are supported by technical standards, decades of practical experience, and real examples from our work. You will also find graphical diagrams that will help you understand the relationships that are hard to describe with words alone.

If you are looking for a deeper insight into a specific topic, our Knowledge Center contains further specialized articles, for example How to choose piping for potable water distribution: multilayer vs. copper vs. plastic, or Piping sizing for potable water: how to calculate diameter and length. Here, we focus on practical questions that actually arise before purchase and during installation.

1. What is potable water piping made of and why does it matter?

The material of the piping is not just a technical formality. It directly affects the quality of the water flowing through it, the lifespan of the entire distribution system, the ease of installation, and the final cost. Today, three main material groups are commonly used for potable water distribution:

Copper – a classic, proven, bacteriostatic material suitable for both cold and hot water, joined by soldering or compression. Rigid, requires fittings in every bend.
Multilayer piping (PEX-Al-PEX or PE-Al-PE) – a combination of plastic and an aluminum insert, flexible, non-corrosive, easy to install, shape-stable after bending. Suitable for most domestic distribution systems.
Plastic piping (PP, PEX, PE) – cheap, light, low-maintenance, but not always shape-stable; some types are unsuitable for continuous temperatures above 70 °C.

From a hygiene perspective, all materials used in potable water distribution must have the appropriate certifications, especially compliance with regulations for contact with drinking water. Copper has natural antibacterial properties, and multilayer piping is inert – it does not chemically react with water. More on this topic can be found in the article Hygiene and material safety of potable water piping: what you need to know.

2. What is multilayer piping and why is it so popular?

Multilayer piping (in English: multilayer pipe, abbreviated in practice as MLP) has an inner plastic layer (PEX or PE), an aluminum foil in the middle, and an outer plastic layer again. These three layers are firmly bonded together with adhesive glue. The result is a pipe that combines the advantages of both worlds – the shape stability of aluminum and the chemical resistance of plastic.

In practice, this means: bend it by hand into the desired shape, and when you let go, it will stay in place. You don't need to reach for a fitting every time you make a turn. On long straight sections, it can be guided in a track or behind drywall without the need to fix it every 30 cm (linear expansion is significantly lower than with pure plastic).

Typical dimensions you will encounter in domestic distribution: 16×2 mm, 18×2 mm, 20×2 mm – the first number is the outer diameter, the second is the wall thickness. The inner diameter can be calculated easily: 16 − 2×2 = 12 mm inner diameter for a 16×2 pipe.

Concrete examples: Multilayer pipe IVAR Turatec 16×2 (200 m reel) is suitable for cold water to taps and for floor heating; Multilayer pipe IVAR Turatec 20×2 (100 m reel) is typically used for main horizontal distribution or risers when higher flow demand is expected.

3. When to choose copper piping and when multilayer piping?

This is probably the most common dilemma. Short answer: both solutions are reliable and both have their ideal conditions of use. Longer answer:

We recommend copper when:

you want maximum rigidity and dimensional stability (e.g., at taps where the pipe protrudes from the wall and must support the faucet without sagging),
you are dealing with an external or semi-external distribution where the aesthetics of visible piping are important,
you have hard water with high pH and prefer a proven material without concerns about oxygen diffusion,
you are renovating an older copper distribution – material compatibility is simpler.

We recommend multilayer piping when:

you need a quick and clean installation without soldering (a cutter, a deburring tool, and a crimping pliers or compression fittings are enough),
the pipe will run under the floor, in monolithic concrete, or in masonry grooves – flexibility and resistance to moisture are clear advantages here,
you want to minimize the number of joints and fittings on long sections (thanks to flexibility),
you are dealing with a distribution combined with floor heating – the same material, the same fittings.

A comparison of both materials is dedicated to a separate article in our Knowledge Center: Multilayer piping vs. HEPWORTH: which is better for your distribution.

4. What does the marking PN10 and temperatures +70 °C / +95 °C mean?

PN is an abbreviation from the Latin Pressio Nominalis – nominal pressure. PN10 means that the pipe is designed and certified for a maximum working pressure of 10 bar (1 MPa). For domestic water installations, this value comfortably covers the typical pressure in the distribution network (usually 3–6 bar) as well as pressure surges when a tap is suddenly closed.

The temperatures +70 °C and +95 °C indicate at what temperature the given pressure parameter is guaranteed. The pipe IVAR Turatec 18×2 has PN10 at +70 °C and PN10 at +95 °C – in practice, this means that it can withstand 10 bar for a long time at 70 °C, and the same at higher temperatures close to 95 °C. This is an important parameter for hot domestic water (HDW), where the temperature in the tank or during circulation can reach 60–70 °C, and even 80 °C during disinfection heating.

Important practical note: PN does not remain constant at different temperatures. Pure plastic pipes (PP, PEX) have significantly lower allowable pressure load at high temperatures. This is exactly why multi-layer pipes with an aluminum layer outperform purely plastic solutions when used for both cold and hot water – aluminum "holds" the shape and prevents material deformation under pressure and temperature.

A more detailed explanation of pressure classes can be found in the article Pressure classes PN10 and temperatures +70 °C vs. +95 °C: what they mean for your distribution system.

5. What pipe diameter do I need for my household?

This is a question where customers often guess instead of looking at specific numbers. The basic logic is simple: the more outlets and the higher the simultaneous consumption, the larger the diameter of the supply line. But be careful – an unnecessarily large diameter is also not good (longer time for hot water to flow, larger volume of stagnant water in the pipe).

Practical recommendations for a family house with standard equipment (4–6 outlets):

Main supply to the house: min. DN15 (outer diameter 22 mm for copper or 20 mm for multi-layer pipe), recommended DN20 for a larger house or if the supply is longer than 10 m.
Horizontal distribution (main branches): DN15, or DN12 (16 mm multi-layer) for shorter branches with 1–2 outlets.
Connection to an individual outlet (tap, WC, sink): DN10 or DN12 – that is, 15 mm HEPWORTH or 16 mm multi-layer pipe.

Practical example: a three-room apartment after renovation, bathroom + WC + kitchen = 7 outlets. The main distribution is run in 20 mm multi-layer pipe, branches to the bathroom and kitchen in 18 mm, and connections to taps and cisterns in 16 mm. This structure ensures sufficient flow even with simultaneous use at two points without significant pressure drop.

A detailed calculation of dimensions including pressure losses and Reynolds number can be found in the article Dimensioning pipes for potable water: how to calculate diameter and length.

6. Can multi-layer pipe be used underground or in a concrete floor?

Yes, and this is one of its biggest advantages. Multi-layer pipe is commonly laid directly into the concrete mix of the floor (with or without protective casing, depending on specific conditions), into grooves in masonry, and underground. Key conditions:

No joints in the body of the structure: joints (fittings, crimped or compression) must be accessible. The entire section laid in concrete or underground must be from one piece of pipe without interruptions.
Protective casing underground: when laid underground outside the building, corrugated protective casing is recommended to protect against mechanical damage and to allow pipe replacement without excavation.
Depth of laying: minimum 80 cm below ground level (below the frost line in Central Europe), usually 100–120 cm for garden connections.
Soil pH: in aggressive soils (low pH, high sulfate content), additional protection is advisable; however, multi-layer pipe is more resistant to common soil conditions than copper, which can corrode from the outside in acidic soils.

Example from a project: renovation of a family house, the customer wanted to run cold water from the technical room through the entire foundation to the garden. We used multi-layer pipe 20×2 in a 200 m coil (in this case we took 100 m from the coil) – the entire 14 m section under the foundation without a single joint. Result: clean, reliable distribution with minimal risk of failure.

7. Is copper HEPWORTH pipe suitable for potable water?

Yes, and it is among the traditional, proven solutions. Copper has a long history of use in potable water supply – decades of practical experience, hundreds of millions of meters installed worldwide. Its bacteriostatic properties (copper inhibits the growth of certain bacteria including Legionella pneumophila) are even an advantage in hygienically sensitive systems.

HEPWORTH pipe 15 mm is the most commonly used size for connections to sinks, WC, and kitchen taps. HEPWORTH 22 mm is used for main horizontal distribution or in cases where higher flow is required.

Practical note: Copper is not suitable in the presence of soft water with a low pH (below 7.0). In such water, copper gradually leaches into the drinking water and causes corrosion of the pipe walls. In areas with softened or mountain water, multilayer pipe is a better choice. Before investing in copper piping, find out the water quality in your area – local water utility will provide the information.

8. How are different types of pipes connected – what fittings do I need?

This is a practical question, and sometimes customers buy the pipe and forget about the fittings, or buy fittings incompatible with the pipe. Basic rule: the fitting system must be designed for the specific type of pipe and its outer diameter.

For multilayer pipe, there are two main connection methods:

Compression (screw) fittings: the pipe is inserted into the fitting and the nut is tightened. Simple, removable, suitable for visible and accessible piping. No special tools are required.
Press fittings: the pipe is inserted into the fitting with O-rings and the joint is compressed using a pressing pliers. Solid, permanent, suitable for embedding in walls. Requires a pressing tool (can be borrowed or an installer can be called).

For copper HEPWORTH pipe, you have two options:

Soft soldering: back soldering with a capillary fitting, solder and soldering iron. A proven method, requires skill and caution (fire near wood, insulation). The result is strong and durable.
Pressing (press fittings): a modern alternative without fire, fast and reliable. Increasingly popular especially in renovations of older houses, where the risk of fire during soldering is undesirable.

A detailed step-by-step guide can be found in the articles Installation of multilayer pipe step by step: tools, procedure, mistakes and Installation of copper HEPWORTH pipe: soldering or pressing.

9. Can I combine different types of pipes in one system?

Yes, combining is common and sometimes the most sensible choice. For example, during the renovation of an older house with an existing copper piping system, you can continue from a certain point with new multilayer pipe. Or you can have a copper riser and switch to multilayer pipe from the floor distributor to individual rooms.

When combining, the correct transition fitting is essential – special fittings with a copper or brass thread on one side and a compression or press fitting for multilayer pipe on the other side are available. These transition fittings are a standard part of the product range at any good wholesale store.

What you must never combine: different press fitting systems (e.g., one manufacturer may not be compatible with the profile of another manufacturer) and different diameters without the appropriate reducer.

10. How to properly bend multilayer pipe?

Multilayer pipe has a recommended minimum bend radius, which depends on the outer diameter. Approximate values:

16 mm pipe: minimum bend radius 50–80 mm (bend by hand, without spring)
18 mm pipe: minimum bend radius 60–90 mm
20 mm pipe: minimum bend radius 80–100 mm

When bending by hand (without tools), the rule is: slowly, evenly, without sudden changes. The pipe must not be broken or have sharp bends – this would significantly reduce the cross-section and damage the aluminum layer. For smaller diameters (16–18 mm), most experienced installers can do it by hand. For larger diameters, a bender is recommended – a manual one with a spring or a mechanical one with a roller.

Common mistakes from practice: a customer tries to bend cold pipe to 90° without tools and too quickly – the result is flattening at the bend. A flattened pipe must be replaced with a new piece – it is not just an aesthetic flaw, but a real reduction in cross-section and risk of increased pressure resistance.

11. How long does pipe for drinking water last?

With proper installation and normal water quality:

Copper: 50–100 years. Historical copper piping systems from the 50s–60s are still functional in many houses. The main enemies are aggressive water (low pH) and mechanical damage.
Multilayer pipe (PEX-Al-PEX): manufacturers guarantee 50 years under specified conditions (temperature, pressure, water quality). In practice, experience beyond 25–30 years is not yet available, as this material became widespread in the 90s, but all signs indicate that the guarantees are realistic.
Plastic pipe PP/PEX: 25–50 years, depends on material quality and operating conditions.

The lifespan of the pipe is shortened by: frequent temperature shocks (rapid alternation of hot and cold water), aggressive water, mechanical damage during installation, and unsuitable chemical cleaners.

12. What to do if I have a leaking connection or a small leak in the piping?

First rule: never seal a leak and hope it will hold. Moisture behind the drywall or in the wall will cause mold and eventually structural damage. Every leak must be addressed.

With compression fittings: try to gently tighten the nut. If that doesn't help, disassemble the fitting, check the olive and O-ring (replace with a new one), shorten the pipe by a few millimeters (if it was inserted insufficiently), and reassemble the fittings. With crimped fittings and soldered joints, disassembly is not possible – you need to cut out the damaged section and insert a new piece with fittings.

More about the causes and solutions for leaks can be found in the article Common faults and leaks in potable water piping: causes and solutions.

Most frequently asked questions by customers (FAQ)

Can I use multilayer pipe for potable water without any certification and without worrying about health?

Yes, but only if it is a product with the appropriate hygiene certificates for contact with potable water. Quality manufacturers like IVAR include these certificates as standard with the technical documentation. Always confirm before purchase that the product is explicitly certified for potable water – not all multilayer pipes are the same, and some cheap imports may not have certification or may have it only on paper. Purchasing from a verified e-shop or wholesaler minimizes this risk.

What is the difference between a 200 m and 100 m coil of pipe – why buy a larger coil?

Simply: fewer joints. On long sections where you would have to make a joint in the middle (e.g., in the floor or behind plaster), a larger coil allows you to run the entire section from one piece. Every joint is a potential weak point – not because it is of poor quality, but because it is an additional component that could fail over time. For larger renovations or new builds, a 200 m coil is more economical per meter and helps minimize the number of joints.

Is it possible to save on pipe and buy less than I calculated?

Experience clearly says: never plan for so-called "exactly". Always add at least 10–15 %, ideally 20 %, to the calculated length as a reserve. Reasons: during bends you will use more pipe than on a straight section, in case of a mistake during cutting or installation you will need a replacement piece, and any future expansion of the piping (an additional tap, a renovated bathroom) will be appreciated when you still have some of the same pipe left.

Can I use potable water pipe for technological water (garden irrigation, cooling circuits)?

Technically yes – pipe certified for potable water will function without problems in technological applications. The reverse question is: pipe certified ONLY for technological purposes must not be used for potable water. For garden irrigation or cooling circuits, you can safely use the same multilayer pipe as inside the house – it is even advantageous because you don't have to combine different materials and fittings.

How can I tell that the pipe in the wall is damaged or leaking when I can't see it?

The most common signs of hidden leaks: unexpected increase in water consumption on the water meter (compare monthly bills), damp spots on the plaster or drywall, warping of wooden flooring, mold in room corners, pressure drop when all taps are closed. For certainty, you can close the main shut-off valve and watch the water meter – if it is turning, you have a leak. In case of suspected major problems, a thermal camera (rental or a chimney sweep/technician with equipment) will help by showing temperature anomalies in the wall.

Is it necessary to insulate potable water pipe?

For cold water: insulation is not required for internal piping, but when running through unheated areas (basement, attic, exterior) thermal insulation is essential to prevent freezing. For hot domestic water (HDW): insulation of the piping is very energy efficient – without it, HDW will cool down during stagnation in the pipe and every time you use it, you have to let several liters of cold water run before hot water arrives. Insulation with a minimum thickness of 20–30 mm (foam insulation, lambdavalue approx. 0.04 W/mK) reduces heat losses in HDW piping by 60–80 %.

Conclusion: What to take away from this article

The distribution of potable water is infrastructure that is not focused on in a typical household until it stops working. That is exactly why it is worth doing it right the first time – choosing the right material, the right diameter, the right joining method, and the right length. Customers who take the time to think it through and possibly consult never end up saving on the wrong things.

If you have read all the way to here and still have questions about a specific dimension or application, also check out other articles in our Knowledge Center – you will find detailed material comparisons, dimension calculations, installation procedures, and hygiene requirements there. And if you are looking for a specific product, in the category pipe for potable water distribution you will find a complete range including IVAR Turatec multilayer pipes and HEPWORTH copper pipe in various diameters and lengths.

Do you have a question about this topic?

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