Step-by-step installation of PPR pipes – welding, tools, procedure

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Step-by-step installation of PPR pipes – welding, tools, procedure

PPR pipes are now the standard for cold and hot water supply in single-family homes, apartments, and also in commercial buildings. The reason is simple – the material is durable, hygienically safe, cost-effective, and with proper installation, it can last for decades without any maintenance. However, the phrase "with proper installation" is key. I have seen many reconstructions where the plumber connected the pipes quickly, without sufficient heating, or without understanding what actually happens during polyfusion welding. The result – leaky joints, deformed sockets, and in the worst case, a pipe that collapsed under pressure even before commissioning. This article will show you the entire process from selecting tools to pressure testing, just as an experienced plumber with years of practice would show you.

If you are just deciding whether to go for PPR at all, I recommend reading our article PPR vs. copper vs. PEX – comparison of materials for water supply systems, where all three most commonly used systems are compared in detail. If you need help with selecting the diameter, check out What PPR pipe diameter do I need – calculation based on pressure and flow.

What is polyfusion welding and why it works

PPR stands for polypropylene random copolymer – a thermoplastic that softens and becomes pliable when heated to a certain temperature. This very property is the basis of polyfusion welding (also known as hot tool welding or socket fusion welding). It is not gluing or mechanical joining – the pipe and fitting literally merge into one piece of material at the correct temperature. Once the joint cools down, there is no boundary, just one continuous polypropylene section.

The welding temperature is around 260 °C. At this temperature, the surface of the pipe and the inside of the fitting melt to a depth of several tenths of a millimeter. When you press them together, the molten material mixes and after cooling, a homogeneous, strong joint is formed. Three factors are crucial: the correct temperature of the tool, precise heating time, and immediate, direct pressing without rotating.

The welding zone (yellow) is where the material of the pipe and fitting interpenetrate. After cooling, this joint is stronger than the pipe itself – a well-made PPR joint is never the weakest point of the installation.

Required tools and materials – what to prepare before starting

One of the most common mistakes I see in amateur installations is underestimating the preparation of tools. People come to the site with a polyfusion welder, but forget to bring degreaser, a level, or even a measuring tape. Then they improvise and the result reflects that. Here is a complete list of what you need:

Polyfusion welder (thermostatically regulated) – the basic tool, without which you cannot proceed. It must be equipped with heating sleeves (mandrels) in the sizes of the pipes you are going to weld. The sleeves must be clean and not stuck – contaminated sleeves are a direct path to faulty joints.
PPR pipe cutters – for cutting pipes. For home use and diameters up to 63 mm, we recommend our Standard Cutters up to 63 mm. They provide a clean, perpendicular cut without burrs, which is essential for a quality joint. Any slanted cut will show up as a weak point when inserted into the fitting.
Marking tool for insertion depth – a marker or scribe to mark the depth to which the pipe must be inserted into the fitting. Without this marking, you risk inserting the pipe too little or too much.
Surface degreaser – isopropyl alcohol or special PPR cleaner. Every surface must be clean, dry, and free of grease before welding.
Tape measure and pencil – accurate measurement is fundamental. A pipe cut 5 mm too short means the entire section has to be redone.
Level and laser level – horizontal and vertical alignment of pipes is important not only for aesthetics, but also functionally (venting, draining condensation).
Stand or workbench for the welder – the welder must be stable and secure. A freely placed welder on an unstable base is a safety risk.
Brushes and paper towels – for cleaning the heating sleeves between welds.
Stopwatch or watch with a second hand – heating times are precise and must be followed.

For larger diameters (over 63 mm), special push-fit welders are used and the procedure is slightly different, but for a typical apartment installation (sizes 20, 25, 32 mm), standard equipment is sufficient.

Heating time table according to pipe diameter

Heating times are standardized and their non-compliance is the most common cause of faulty joints. Too short a time = the material does not melt deeply enough. Too long a time = the material overheats, the socket of the fitting deforms, and the joint loses its geometry. These values are valid at ambient temperature of about 20 °C and welder temperature of 260 °C:

Pipe diameter (mm)	Heating time (s)	Joining time (s)	Cooling time (min)
16	5	4	2
20	5	4	2
25	7	4	2
32	8	6	4
40	12	6	4
50	18	6	4
63	24	8	6

Important note: at low temperatures (below 10 °C, for example during winter installation in an unheated boiler room), extend the heating times by 50 %. Cold material conducts heat away more quickly and without compensation, the joints will not fuse properly.

Step-by-step installation procedure

We will now move on to the actual work procedure. I will describe it as I would explain it to an assistant on my first job – specifically, without skipping any „obvious“ steps, because it is precisely these that people most often fail at.

Step 1 – Preparation and measurement

Before making any cut, draw a layout diagram – where everything goes, what fittings you will need (90°, 45° elbows, T-pieces, reducers, straight couplings). Calculate the lengths of individual sections. Remember: the length of the pipe is measured from end to end, including the depth of insertion into the fitting. The depth of insertion depends on the diameter:

⌀20 mm → insertion depth approx. 14 mm
⌀25 mm → approx. 16 mm
⌀32 mm → approx. 18 mm
⌀40 mm → approx. 20 mm
⌀50 mm → approx. 22 mm
⌀63 mm → approx. 24 mm

If you cut the pipe without considering the insertion depth, your entire layout will end up shorter than expected and you will run into problems when connecting to the last point (e.g. a radiator or valve). This is a basic, but very common mistake.

Step 2 – Cutting the pipe

Always cut the pipe at a right angle – the cut must be 90° to the pipe axis. A slanted cut will cause the pipe to not insert evenly into the fitting, the material will melt unevenly and a weak spot will form. Professional pipe cutters up to 63 mm STANDARD are optimized for this – align them correctly and make sure the pipe lies perpendicular to the jaws. Do not press too quickly – slow, even pressure gives a cleaner cut than a sudden push.

After cutting, check the cut – it must not be jagged, slanted or have scratches. If it is, cut the piece again. Do not just throw away the cut-offs – short pieces can be useful for filling gaps and test joints.

Step 3 – Marking the insertion depth

Take a marker or scribe and mark the insertion depth on the end of the pipe (see the values above). This mark will tell you during joining whether the pipe is inserted deeply enough. It is a simple step, but without it you are working blindfolded.

Step 4 – Cleaning the surface

Wipe the outside of the pipe end and the inside of the fitting socket with a cloth dampened with isopropyl alcohol or special PPR cleaner. Let it dry – usually 30 seconds is enough. No grease, sweat or dust must remain on the surfaces that will be heated. A greasy surface will prevent proper melting and the joint will look good but will fail during the first pressure test or when hot water is used.

Step 5 – Heating

The polyfusion welder must be heated to 260 °C (±10 °C). Most quality welders have a thermostat and an indicator light or display. Wait until the welder actually reaches the working temperature – at least 5–10 minutes after turning it on, not less.

Push the end of the pipe onto the outer mandrel (nose) of the heater and the inside of the fitting onto the inner part (socket) of the heater. Do both simultaneously, evenly, without rotating. Start the stopwatch and observe the heating time according to the table. During heating, do not touch the material, do not move the pipe or fitting, do not apply additional pressure – let the heat do the work.

Step 6 – Joining

After the heating time has elapsed, smoothly and quickly remove both parts from the heater – the movement must be straight, not rotational. Immediately push them together: insert the pipe into the fitting with one straight motion without rotating all the way to the marked line. The entire joining process must be completed within the time limit (4–8 seconds depending on the diameter). If you hesitate, the material will harden on the surface and the joint will be defective.

When the pipe is inserted to the mark, a uniform „bead“ of molten material should appear around the entire circumference of the joint. This is a positive sign – molten material extruded outward means there was enough material and the joint is full. If the bead is not uniform or is missing, the joint is suspicious.

Step 7 – Cooling and fixing

Hold the joint in a straight position without movement for the entire cooling time (2–6 minutes depending on the diameter). This is the moment where most people make a mistake – they release the joint too early and a slight movement changes the geometry of the connection. Result: a small angular deviation that is not visible during installation, but the pipe will not fit straight into the fittings.

During cooling, do not cool the joint with water or otherwise artificially – let it cool naturally. Forced cooling creates internal stress in the material.

Installation of Ball Valves and Fittings in PPR System

Every plumbing system requires shut-off devices – at least one main shut-off after the water meter and shut-offs for individual branches. In PPR systems, either PPR ball valves with weldable necks or transition pieces for threaded fittings (external/internal thread G1/2", G3/4", G1") are used. For shutting off the entire supply (e.g., at the water inlet to the house or after the water meter), the robust Ball Valve, 50 (99912650) is ideal – for a DN50 diameter, which corresponds to a standard water supply pipe in family homes.

When installing a ball valve into a PPR system, the same principles apply as with a regular joint. In addition, it is important to:

Mount the valve in the correct position – most ball valves are designed for horizontal or vertical piping. Check the flow direction (arrow on the valve body).
During welding, open the valve fully – this prevents overheating of the internal ball seal during heat transfer from the welding process.
Close or open the valve fully only after the joint has completely cooled down (at least 30 minutes after installation).
Use Teflon tape or threaded sealant for threaded transitions – never force it. Over-tightening the thread in a PPR fitting may crack the neck.

If you are interested in the broader topic of fittings in PPR systems, please see our article Ball Valves in PPR Systems – Selection, Installation and Maintenance.

Securing and Routing of PPR Pipes

PPR pipes must be properly secured – not too tight (the material expands thermally and needs space), nor too loose (vibrations and gravity will cause sagging). Maximum distances between supports (clamps) according to diameter:

⌀20 mm: every 1.0 m (horizontal), every 1.5 m (vertical)
⌀25 mm: every 1.2 m / 1.7 m
⌀32 mm: every 1.5 m / 2.0 m
⌀40 mm: every 1.7 m / 2.3 m
⌀50 mm: every 2.0 m / 2.7 m

The thermal expansion of PPR is relatively high – about 0.15 mm/(m·K). For hot water (60 °C) and a 10 m long pipe, this means an expansion of about 67 mm compared to cold water (15 °C). Therefore, in long runs, compensating bends or expansion loops are introduced – typically a "U" shape made from standard elbows, where the free length of the loop absorbs thermal movement. Without compensation, stress accumulates at fixed supports and joints will crack – not immediately, but after several years of cyclic loading.

Working in Confined Spaces and Common Practical Situations

In jobs, I often encounter the situation where people have mastered the technique perfectly in open space (in a workshop, on the floor), but when they have to work in a shaft or behind a bath, the results are poor. In confined spaces, it is difficult to keep the axes aligned and hard to hold the welder. Here are a few practical tips:

Premount as much as possible on a table – if the route allows, weld as much as possible into preassembled units outside the wall. Then, insert the complete assembly into the shaft and weld only the final joints.
Use extension attachments – some welders allow for cable extensions so that the heating element can reach deeper into the shaft.
Mark the position on the wall beforehand – level the route before drilling, not after installation. PPR pipe goes in once and precisely.
Allow enough time for cooling – in confined spaces, it is tempting to continue immediately, but a joint hidden from view cools down more slowly (poor heat dissipation). Expect a 20–30 % longer cooling time.
Check the joint alignment using a level – a small digital inclinometer at the end of the welded pipe will show whether the route is straight before embedding the pipe into the wall.

Pressure Test for Leak Tightness After Installation

After completing the entire installation and before covering or embedding into walls, a pressure test must be performed. This is a legal requirement for family homes and apartments, and without it, you cannot be sure the installation is leak-tight. Procedure:

Close all end points (where radiators will be, leave the pressure gauge open).
Fill the system with water and bleed it – open all the highest points until water flows out without bubbles.
Using a hand pump, increase the pressure to 1.5 times the working pressure (typically 6 bar working pressure at 9 bar test pressure).
Let the pressure act for at least 30 minutes – monitor the manometer. A pressure drop of more than 0.6 bar indicates a leak.
Visually inspect every joint – water droplets, moisture, condensation on the joints.

If you find a leaky joint, depressurize and drain the system, uncover the problematic joint, and replace it. A leak-tight PPR joint cannot be repaired – it must be cut out and a new one welded in. For more on this topic, see our article Leak Tightness of PPR Joints – Most Common Installation Errors and How to Fix Them or What to Do If PPR Pipe Leaks or Cracks – Repair Without Replacement.

Common Mistakes and How to Avoid Them

After years of job experience, I have compiled a list of mistakes I repeatedly see – regardless of whether it is an experienced plumber or a skilled DIY enthusiast:

Rotating the pipe during joining – the most common mistake of beginners. The movement must always be straight, never rotational.
Insufficient heating (short time) – the joint looks good, but during the pressure test or when hot water is first used, it separates.
Overheating (long time or too high temperature) – the material melts, the neck deforms, and after insertion, it is no longer round.
Fatty or wet surfaces – degreasing seems unnecessary until you see a joint where the molten material has separated from the fitting surface.
Moving the joint during cooling – even slight realignment "just a few degrees" during the first minute of cooling creates a fatigue crack in the material.
Dirty heating elements – burned material residue on the heating element transfers to the new joint and disrupts it. Clean the heating elements after each welding with a hot cloth while the tool is still hot.
Installation at low temperatures without compensation – in winter, allow the material to acclimate for at least an hour in an environment above 10 °C before installation or extend the heating times.

Thermal insulation of PPR pipes

Many installations are technically flawless but physically poorly designed – hot water cools down in non-insulated pipes before reaching the tap, cold water condenses moisture on the surface of the pipe. Insulation is not a luxury, it is part of a proper installation.

For hot water (temperature above 50 °C), use mineral wool or rigid PUR insulation with a thickness of at least 20–30 mm for standard diameters. For cold water in warm areas (basement in summer, utility room) 9–13 mm foam insulation (e.g. Armaflex) is sufficient. Insulation also protects the pipes from mechanical damage when covered with drywall or embedded in walls.

The topic of thermal and pressure resistance is discussed in more detail in the article Thermal and pressure resistance of PPR pipes – what you need to know before buying.

Most frequently asked questions (FAQ)

Can I weld PPR pipes without a professional welding tool, for example with a hot air gun?

No. A hot air gun cannot evenly heat the inside of the fitting and the outside of the pipe simultaneously to the correct temperature of 260 °C. The result may look similar, but it will be metallurgically unconnected – the joint will separate under the first pressure load or after heating the water. For PPR welding, you need a real polyfusion welding tool with a thermostat and the correct collars. Welding tools can be borrowed from tool rental services and for a one-time home installation, this is a reasonable choice.

What is the maximum working pressure of PPR pipes?

It depends on the PPR pipe class (PN10, PN16, PN20, PN25) and the temperature of the medium. At cold water (20 °C), PPR PN20 can withstand 20 bar, but at hot water 70 °C the resistance drops to about 8–10 bar. In apartment distribution systems, the working pressure is around 3–6 bar, so PN16 or PN20 is the standard for hot water. For heating systems with temperatures above 70 °C, use only PN25.

How long should I wait after welding before I can fill the system with water?

I recommend waiting at least 2 hours after the last joint at room temperature before pressurizing the system. The actual cooling of the joint takes 2–6 minutes, but in a complete installation, some joints are heated again during the assembly of other parts and the overall thermal state of the system takes a long time to equalize. Professional plumbers usually wait 30–60 minutes after completing the entire installation, longer at low temperatures.

Can I connect PPR directly to steel or copper pipes?

Yes, but not by direct welding. Transition fittings with a metal threaded insert (brass internal or external threaded sleeve) are used to connect different materials. These fittings have a PPR neck on one side (for welding) and a metal thread on the other side (for threaded connection to steel or copper pipes). Always use sealing – Teflon tape, thread sealant or sealing compound according to the thread size – for threaded connections.

What to do if the collar sticks to the fitting during installation?

This can happen if the collar was dirty or if the fitting overheated. Never pull the fitting by force – you will damage the collar and possibly the welder. Leave the welder turned on, wait 1–2 minutes – the heat usually releases the stuck joint. If not, carefully use a wooden wedge from the side (never a metal tool that could scratch the Teflon coating of the collar). After the incident, clean the collar and check the surface.

Can I run PPR pipes underground or in the floor?

Yes, PPR is suitable for running in a concrete subfloor or underground provided it is properly protected. Always protect the pipe with a protective sleeve (flexible pipe or corrugated pipe) in concrete to allow for thermal expansion. For underground laying outside the building, ensure a minimum burial depth of 60 cm (frost zone) and use thick-walled PN20 or PN25 pipe. Underground joints must be reliable, as leaks are only discovered after the foundation gets wet.

Conclusion

Installation of PPR pipes is a process that can be mastered even without years of experience, provided you understand the process and have the right tools. The key is in the details: a clean cut, degreasing, precise heating time, direct joining without turning and patience during cooling. None of these steps is complicated, but each of them must be done correctly.

If the topic of tools seems too extensive to you, take a look at our separate guide How to correctly use PPR pipe scissors and polyfusion welder. For those tackling the entire project from scratch, a good starting point is also the article How to choose the right PPR pipe system for your home. And if you have more common questions before purchasing, you will find them in the section Frequently asked questions about PPR pipe systems.

A properly installed PPR system is quiet, leak-free and maintenance-free for decades – that is its biggest advantage. It is worth doing it right the first time.

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.