Installing PEX Press Fittings Step by Step: Tools and Procedure

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Installing PEX Press Fittings Step by Step: Tools and Procedure

Pressing PEX and PEX/AL/PEX pipes is one of the most common jointing techniques used today in sanitary and heating systems. It is fast, reliable, and permanently tight when done correctly – with no need for soldering, gluing, or complicated tools. Nevertheless, in practice we encounter mistakes that arise not from ignorance of the technology itself, but from carelessness at a specific step: a poorly cut pipe, unsuitable tools, a forgotten press ring, or pressing on a wet joint. In this article, we will go through the entire fitting installation procedure – from tool preparation, through the pressing itself, to verifying tightness – as we see it in real practice among plumbers with dozens of jobs behind them.

What Are PEX Press Fittings and Why They Are Installed This Way

Press fittings for PEX and PEX/AL/PEX systems are fittings, usually made of brass, that are not joined by thread or adhesive, but by pressure-deforming a press ring (sleeve) around the pipe using special pliers or hydraulic tools. The principle is simple: the pipe is inserted onto the fitting, the press ring is placed over it, and it is then permanently compressed by pressing jaws – the resulting joint is mechanically rigid and watertight.

This technology became widespread mainly because it eliminates the risk associated with open flame (soldering copper pipes), shortens installation time, and does not require a long curing period (as with gluing PVC). The joints can be pressurized immediately after pressing and verification. You can find more about the advantages of this method compared to screw fittings in the article Pressing vs. Screw Fittings: Which Is Better for PEX Systems in our Knowledge Center.

Overview of Required Tools

Before starting installation, you need to prepare the right tools. Using unsuitable tools is one of the most common causes of leaks – the pressing jaw must fit precisely to the profile of the press ring used by the given manufacturer and dimension.

Basic Tool Set

PEX pipe cutter – a rotary cutter or precision saw with a guide. An ordinary knife or pipe scissors without a guide are not sufficient – the cut must be perpendicular to the pipe axis, with a tolerance of ±1–2°. For PEX/AL/PEX pipes, we recommend a rotary cutter with a special blade for composite pipes, not a regular plastic pipe cutter.
Deburring tool (deburring cutter) – essential for PEX/AL/PEX pipes, since the inner edge of the cut must be freed of the aluminum burr, which would otherwise prevent proper insertion of the fitting or cause leakage. For plain PEX, a deburring tool is not always necessary, but is always beneficial.
Calibrator (calibrating hammer or mandrel) – PEX pipes have shape memory, and after cutting the end may be slightly oval. The calibrator restores the round cross-section before fitting insertion. It is usually not needed for PEX/AL/PEX (the AL layer holds the shape), but for soft PEX in larger dimensions (25 mm and above) it is good practice.
Press pliers or hydraulic press – either manual pliers (suitable for dimensions up to 25 mm, smaller number of joints), or battery-powered/hydraulic press pliers (professional use, dimensions up to 63 mm). The pliers require the correct jaw for the specific dimension and press ring profile type.
Tape measure, pencil, straightedge – for measuring and marking the pipe insertion depth.
Pressure test equipment – a manometer or hand pressure pump to verify tightness after installation is complete.

Types of Press Rings and Their Compatibility

On the Slovak market, we mainly encounter two press ring profiles: U-profile and TH-profile (sometimes also referred to as H-profile). These profiles are not interchangeable – each requires different jaws. Before purchasing tools, always check which profile your fitting supplier uses.

Fittings in the PEX/AL/PEX press fittings category at Atria.sk use a standardized profile – when ordering, we recommend checking the technical data sheet and verifying compatibility with your tool. If you are unsure, the article How to Choose PEX/AL/PEX Press Fittings: Type, Size and Compatibility in the Knowledge Center covers this in detail.

Pipe Preparation: Cutting, Deburring, Calibration

Joint quality is determined before you even pick up the press pliers. Pipe preparation is a critical phase that many plumbers underestimate because they are in a hurry.

Cutting the Pipe

Always cut the pipe perpendicular to its axis. A slanted cut causes the pipe to not insert evenly to the required depth in the fitting, and pressing will produce a leaky or mechanically weak joint. The deviation from a right angle should not exceed 1–2°.

For PEX/AL/PEX pipes, use a rotary cutter designed for composite pipes, not a regular plastic pipe cutter. A regular plastic cutter will crush the AL layer instead of cutting through it, resulting in an uneven, flattened edge. Some experienced plumbers use a fine saw with a guide and sleeve – this method is slower but precise.

Deburring the Edges

After cutting a PEX/AL/PEX pipe, a small aluminum burr forms on the inner edge, protruding inward. This must be removed with a deburring tool – otherwise it will hinder fitting insertion and may damage the seal or cause turbulent water flow at the joint during operation. It is also good practice to lightly chamfer the outer edge – this makes it easier to fit the pipe onto the fitting.

Calibrating the Cross-Section

Soft PEX pipes, especially in larger dimensions (from 25 mm), may have an oval cross-section after being unrolled from a coil. Before fitting, pass a calibrating mandrel of the corresponding dimension over the pipe end – 2–3 passes are enough to restore the round shape. Skipping this step results in the pipe either not fitting onto the fitting at all, or fitting with a gap on one side, which compromises the tightness of the joint.

Marking the Pipe Insertion Depth

Before inserting the pipe into the fitting, always mark the required insertion depth. Every fitting manufacturer specifies a minimum insertion depth (so-called insertion length) for each dimension – typical values are:

DN 16 mm: insertion depth approx. 17–18 mm
DN 20 mm: insertion depth approx. 19–21 mm
DN 25 mm: insertion depth approx. 22–24 mm
DN 32 mm: insertion depth approx. 26–28 mm

Exact values can be found in the technical data sheet of the specific manufacturer – they may vary slightly. Mark this distance from the pipe end with a pencil or marker. After inserting it into the fitting, check that the mark is exactly at the edge of the press ring. If the pipe is inserted less deeply, there is a risk of leakage or the pipe slipping out under pressure load.

In practice, we have seen a mistake where a technician forgot to mark the depth, inserted the pipe "by eye," and after pressing it turned out the pipe only reached 10–12 mm – less than the minimum. Such a joint may appear tight at 1–2 bar, but will separate under full operating pressure (6 bar). More on this and similar mistakes is described in the article Common Mistakes When Pressing PEX Fittings and How to Avoid Them.

Fitting the Press Ring and Inserting the Pipe onto the Fitting

The order of steps when fitting is precisely defined and must not be swapped. Here is the correct sequence:

Slide the press ring onto the pipe (!) before inserting the pipe into the fitting. This step ensures the ring will be in the correct position. If you forget to slide the ring on beforehand, you will have to pull the pipe back out, slide on the ring, and insert it again.
Insert the pipe onto the body of the fitting with a firm, straight motion – without twisting. Push it in until the pipe edge aligns with the stop limiter (stop) inside the fitting. Check the position against the mark made earlier.
Slide the press ring toward the fitting until it sits in the correct position on the fitting body. The ring must be entirely on the pressing surface – not partially on the bare pipe.

For fittings with an external or internal thread (e.g. PEX press elbow/external thread 16×1/2″), the threaded part is usually already screwed into the threaded counterpart before pressing – always press only once the fitting is mechanically fixed, so that you do not put torsional stress on the joint while using the pliers.

The Pressing Itself: Procedure with Pliers

This is the moment when the joint is permanently closed. Pressing is irreversible – once pressed, the ring cannot be opened and reused. Therefore, check everything once more before squeezing the pliers.

Correct Jaw Position

Fit the press pliers' jaw onto the press ring so that it is precisely centered – most tool jaws have a visible groove or notch that must align with the edge of the ring. The jaw must not extend past the edge of the ring onto the bare pipe or toward the body of the fitting.

Performing the Press

Squeeze the pliers in one smooth motion until fully closed – the pliers must "click" into the end position (or, with a hydraulic tool, the device itself signals cycle completion). Never stop the pressing early – a partially pressed ring will provide neither mechanical strength nor tightness.

After pressing, visually check the shape of the press ring: there should be evenly distributed jaw imprints around its circumference. If the imprints are eccentric or one is missing, the jaw was not properly fitted. In that case, you must cut out the joint and make a new one.

Pressing with Limited Access

In practice, situations arise where the joint is in a corner, against a wall, or in a shaft, and ordinary pliers cannot reach it at the correct angle. For these cases, rotating jaws are available, allowing pressing at an angle of 90° or 180° from the direction of the pliers. This tool is absolutely essential when installing wall elbows – for example the PEX wall elbow/internal thread 16×1/2″ – where the fitting sits flat against the wall and the pliers must press outward from the wall.

Special Situations: Elbows, Reducers, Threaded Fittings

Installing Elbows

When installing elbows, care must be taken so that the pipes do not exert sideways pressure on the fitting. An elbow has its own axis of direction change, and the pipes on both sides must be routed so that they enter the fitting perpendicularly – without pulling or pushing sideways. Sideways pressure fatigues the joint over time and can cause a crack in the fitting wall or push the pipe out.

A standard 90° PEX/PEX press elbow (16) is ideal for changing direction in a system without a threaded connection – both ends are pressed in the usual way. When installing in underfloor heating or behind drywall, always make sure both pipe ends have some slack – otherwise the pliers may not have enough room to fit.

For connecting to a wall (e.g. a standing radiator, convector), wall elbows are designed for this purpose – the PEX wall elbow/internal thread 16×1/2″ has a flange plate used to screw the fitting to the wall. Pressing the pipe onto the fitting can be done before or after attaching it to the wall – it depends on the order of work. From experience, we recommend: first screw the fitting to the wall, then insert the pipe and press it. This avoids a situation where you cannot rotate the pressed fitting into the correct position.

Reduced Elbows and Tees

When changing the system dimension – for example branching from a main DN 20 line to a DN 16 appliance connection – you use a reducing fitting. For example, the 90° reducing PEX/PEX elbow (20×16) changes both direction and dimension in a single fitting, without needing a separate reducer. When installing such a fitting, you press each end separately with the appropriate jaw – jaw 20 on the larger end, jaw 16 on the smaller end.

When to use reducing fittings and when to use separate reducers is discussed in detail in the article Reducing Tees and Elbows: When and Why to Use Them in a System. In short: a reducing fitting is more compact and cheaper than a combination of two fittings, but in a more complex piping layout it can make orientation harder – in that case, separate reducers are clearer.

Threaded Fittings

Fittings with an internal or external thread (e.g. 90° PEX/internal thread elbow 16×1/2″) are pressed on the PEX side in the usual way, while the threaded side is joined conventionally with thread sealant (Teflon tape, hemp fiber with paste, or thread sealing compound). Order of work: first tighten the threaded side onto the counterpart, then press the PEX side. In the reverse order, there is a risk that while screwing you will twist the entire assembled pipe and stress the pressed joint. A detailed procedure for threaded connections can be found in the article Pressing Fittings with Internal and External Threads: How to Properly Connect a System.

Pressure Testing After Completing Installation

After completing all press joints, it is mandatory to perform a pressure test before covering the installation. This step does not take much time but can save you excavation or demolition work later.

Pressure Test Procedure

Close the system (supply valves, plugs on open ends).
Fill the system with water and bleed the air – open every bleed valve until water flows without bubbles.
Using a hand pressure pump, increase the pressure to 1.5 times the operating pressure – for a typical system with a 6 bar operating pressure, this is a 9 bar test pressure. Some designers specify a different value, so always follow the project documentation.
Let the pressure act for at least 30 minutes (2 hours for larger systems) and monitor the manometer. A drop in pressure indicates a leak.
Visually check every joint – a leak is usually visible as a drop or a damp trace.

If a specific joint is suspected of leaking, it must be cut out and replaced with a new one – a press joint cannot be repaired by re-sealing or retightening. A more detailed procedure in case of a suspected leak is described in the article Inspection and Servicing of Pressed Joints: What to Do If You Suspect a Leak.

Typical Mistakes from Practice and How to Avoid Them

Over years of installations and customer consultations, the same mistakes keep recurring. Here is a selection of the most common ones:

Forgotten press ring – the pipe is inserted into the fitting, the technician wants to press it, but the ring is lying next to it on the ground. The pipe must be pulled out, the ring slid on, and the pipe reinserted. Solution: always get into the habit of checking whether the ring is on the pipe before inserting it.
Slanted pipe cut – the pipe does not seat evenly against the stop, and the joint is pressed asymmetrically. Solution: always use a guide or a cutter with perpendicular guidance, never cut the pipe freehand.
Uncleaned inner edge on PEX/AL/PEX – the aluminum burr from the AL layer prevents proper insertion or damages the O-ring. Solution: a deburring tool is mandatory equipment, not an optional extra.
Wrong jaw – a 20 mm jaw on a 16 mm ring, or a U-profile jaw on a TH-profile ring. The result is incomplete or deformed pressing. Solution: always check the dimension and profile before pressing.
Incomplete pressing – the pliers did not reach the end position (jaw hit an obstacle, pliers were weak or worn). Solution: use pliers with a locking function – they cannot be opened after an incomplete cycle. With manual pliers, visually check that the jaws are fully closed.
Sideways pull on the fitting after pressing – the pipe is not sufficiently supported and its own weight or thermal expansion pulls the fitting sideways. Solution: add a clamp or pipe support within 300 mm of each fitting.

Sizing and Choosing the Right Fitting

Choosing the right fitting before installation will save you a lot of work. For typical family homes, main lines are usually sized at DN 20 or DN 25, while branches to appliances (heating, sink, shower) are sized at DN 16. More detailed information on sizing can be found in the article What Diameter of Press Fittings Do I Need for My System.

The choice between elbows, tees, and reducers depends on the piping layout. If you are unsure, read the article Elbow, Tee, or Reducer: Which Fitting Belongs Where in an Installation. In short: an elbow changes direction, a tee creates a branch, a reducer changes dimension – and there are combinations (reducing tees, threaded elbows) that combine these functions in a single fitting.

Safety and Protection at Work

Pressing PEX fittings is relatively low-risk in terms of workplace safety, but a few things should be observed:

Wear protective gloves – sharp edges after cutting pipes can cause cuts.
When working with hydraulic pliers, make sure fingers are not in the path of the jaws.
Never perform a pressure test at pressures higher than specified by the fitting or pipe manufacturer – the maximum test pressure is usually 10–12 bar for typical residential systems.
When working at height (e.g. in a ceiling void or on a ladder), use a stable working platform – pressing with pliers requires a certain amount of physical force, and you could lose your balance from an unstable position.

Quality Assurance: What to Check Before Covering the Installation

Before covering the installation with drywall, flooring, or plaster, we recommend performing the following checks:

Visual inspection of every press ring – jaw imprints must be symmetrical and go all the way around.
Check pipe position – in every fitting, the insertion depth mark must be visible exactly at the edge of the ring, not hidden deeper (a sign of too deep insertion, which is usually not a problem) nor further from the fitting (a sign of shallow insertion, which is a problem).
Pressure test (as described above) – a positive pressure test result gives you the certainty that the installation can be covered.
Photo documentation – before covering, photograph the entire piping system with joints; service technicians and you yourself will appreciate this later when you need to know exactly where the pipe runs inside the wall.

Questions related to choosing fittings and other practical topics are also summarized in the article Frequently Asked Questions about PEX/AL/PEX Press Fittings.

Frequently Asked Questions (FAQ)

Can I press without special tools – for example, using clamp pliers?

No. PEX/AL/PEX press fittings require tools with precisely shaped jaws that ensure uniform deformation of the press ring around its entire circumference and at the correct depth. Ordinary pliers, clamps, or a hammer cannot achieve the required pressure or shape. The result of improvised pressing will be either a leaky or a mechanically unreliable joint. You can also rent the tools from installation material suppliers if you only need them for a one-off job.

Can I take apart a pressed joint and press it again?

No. Pressing is an irreversible process – the press ring is permanently deformed and cannot be returned to its original state or reused on another pipe after pressing. If you need to disassemble a joint (e.g. due to a mistake or repair), you must cut the pipe at the joint, use a new section of pipe, and new fittings. That is why it is important to check the position and type of fitting before pressing.

What is the minimum ambient temperature for pressing?

Most manufacturers specify a minimum installation temperature of +5 °C. At lower temperatures, PEX pipes become stiffer and harder to fit onto the fitting, and there is also a risk that the tool will not reach the prescribed pressing force due to reduced clearances in the pliers' mechanism. In extreme cold, it is better to postpone the installation or temporarily heat the workspace to at least +5 °C.

Can I combine fittings from different manufacturers with the same pipe?

Technically yes, if they have the same pipe outer diameter and the same press ring profile, but experts do not recommend this combination. Different manufacturers may have slightly different tolerances for pipe and fitting outer diameters, which can lead to different pressing forces and results. It is always better to use one system – pipes and fittings from the same manufacturer, or a system-certified combination.

What if the press ring shifts sideways during pressing?

If, upon inspection after pressing, you notice that the ring is shifted or the jaw imprints are not symmetrical, you must consider the joint unreliable and replace it. Do not take the risk – an asymmetrically pressed ring may be leaky or mechanically weak at that specific point, which will only become apparent once the system is under pressure and temperature load. We recommend cutting out the joint and repeating the entire preparation and pressing procedure.

How long does it take to install one press joint?

An experienced plumber with prepared tools can complete the entire process (cutting, deburring, calibration, marking, insertion, pressing, inspection) in 3–5 minutes per joint for dimensions up to 20 mm. For larger dimensions and a hydraulic tool, the time is similar. Measuring and setting up usually take the longest – the actual pressing takes less than 10 seconds. Overall efficiency depends on workplace preparation and tool availability.

Conclusion: A Reliable Joint Is a Matter of Discipline, Not Just Tools

Pressing PEX fittings is a technology that even a fairly inexperienced person can master on their first job – provided they have the right tools, follow the prescribed steps, and perform a pressure test before covering the installation. The biggest mistakes are not technological but human: a skipped step, a forgotten ring, careless measuring. If you work methodically – step by step, as described in this article – you can be confident that the pressed joints will last reliably for decades without maintenance.

If you are looking for specific fittings for your system, check out the entire PEX/AL/PEX press fittings category at Atria.sk – you will find straight couplings, elbows, tees, reducers, and threaded fittings in all common dimensions from 16 to 63 mm.

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