Step-by-step installation of Hepworth profiles

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Step-by-step installation of Hepworth fittings: a comprehensive practical guide

The Hepworth system is one of the proven solutions for wall heating distribution, mainly due to the simplicity of installation, reliability of connections, and availability of a full range of fittings in various diameters. Despite this, we repeatedly encounter situations during projects where even experienced installers make mistakes that only become apparent after the pipe is embedded in the wall – that is, at the moment when the correction requires a lot of work and money. This guide therefore does not only address the installation process itself, but also explains why each step is done in this way, what to pay attention to, and what decisions need to be made even before you pick up your first fitting.

If you are still unsure about which pipe diameters you need for your specific project, we recommend reading the articles What pipe diameters do I need for wall heating? and How to choose the right Hepworth fittings for wall heating from our Knowledge Center – these topics are closely related and the choice of dimensions significantly affects the installation itself.

What are Hepworth fittings and how does their connection system work?

Hepworth fittings are plastic (i.e. polybutylene or PE-RT) press-fit or push-fit fittings designed for water and heating distribution, and in specific versions also for floor and wall heating. For wall heating, they are commonly used in diameters of 10 mm, 15 mm and 22 mm, with each diameter fulfilling a different function in the system: 10 mm for the registers in the wall, 15 mm and 22 mm for horizontal distribution branches and manifolds.

The connection principle of Hepworth fittings is mechanical in essence: the pipe is inserted into the fitting, where it is caught by a steel grip ring and a sealing O-ring ensures the watertightness of the joint. This system is referred to in practice as push-fit or "push and connect" system. It does not require soldering, glue or special tools for the connection itself – just proper pipe preparation and a steady hand.

It is important to understand that the grip ring is inserted unidirectionally – the pipe slides into the fitting easily, but it cannot be pulled back out without a demount clip. This is an advantage in practice (the connection is secure), but also a potential trap in case of incorrect installation. Therefore, it is necessary to plan each connection before inserting.

Tools and accessories you will need

The Hepworth push-fit system does not require anything exotic, but a few accessories can significantly speed up the work and improve the quality of the connections:

Pipe cutter – rotary type for diameters up to 22 mm; a plastic saw is slower and leaves an uneven edge
Insertion depth gauge – a plastic template supplied by Hepworth or you can easily draw it with a marker according to the table
Edge aligner (deburrer/chamfering tool) – removes sharp edges and slightly chamfers the end of the pipe
Demount clips – in case you want to disassemble the connection during installation (you cannot use them after embedding into the wall, but during installation they are life-saving)
Marker or special marking pen for the pipe
Water level or laser level for straight routing
Angle measure and measuring tape
PTFE sealing tape – for threaded connections (not for push-fit connections themselves!)

One practical warning from the field: many installers underestimate the edge aligner. Pipe cut with a rotary cutter always has a slightly fused (deformed) edge – if you do not align it, the grip ring will not sit properly, the O-ring will be damaged and the connection will leak. Over the years of projects, we have seen dozens of leaks that had this single cause.

Pipe preparation before installation – the foundation of the whole process

Pipe preparation is a step that may seem trivial at first glance, but in practice it determines whether the connections will be tight for decades. The procedure is as follows:

1. Cutting the pipe to the correct length

Always measure the pipe with regard to the insertion depth into the fitting. For standard Hepworth fittings, the insertion depths are as follows (approximate values, always check the technical sheet of the specific series):

Diameter 10 mm: insertion depth approx. 23–25 mm
Diameter 15 mm: insertion depth approx. 28–30 mm
Diameter 22 mm: insertion depth approx. 34–36 mm

If you have, for example, a straight coupling 10 × 10 and want to connect two branches, do not forget that each side will consume approx. 24 mm of pipe. This must be subtracted when calculating the lengths of the pipes. An error of 5 mm here and there may seem like a small thing, but with a long row of T-pieces it accumulates into centimeters – and the pipe will not stretch through the wall.

2. Aligning and deburring the edge

After cutting, align the end of the pipe perpendicularly (not diagonally!) and deburr the inner and outer edge. The outer edge must be slightly chamfered – this helps the fitting to guide the pipe without damaging the O-ring. The inner edge is deburred to avoid restricting the flow and promoting the deposition of lime scale.

3. Marking the insertion depth

Mark the insertion depth on the pipe with a marker. After inserting, you will visually check whether the marker stripe is located exactly at the mouth of the fitting. If there is a gap – the pipe is not fully inserted and the connection will be unreliable. This is a simple but absolutely key check.

Installation of straight fittings – step by step

A straight fitting is the simplest type of fitting and is used to directly connect two pipe sections of the same diameter. In a wall heating system, you will use it wherever you need to extend the pipe or connect two sections of a register.

A typical example is the Straight fitting 10 × 10, which is used in wall register distribution systems with a 10 mm diameter. Installation procedure:

Step 1: Preparing both pipe ends

Cut and align both pipes and mark the insertion depth according to the procedure described above. Check that the pipe surface in the joint area is clean, dry and free of mechanical damage (scratches, notches). Even a small notch in the area of the O-ring can lead to a leak.

Step 2: Inserting the first pipe into the fitting

Hold the fitting firmly in your hand and insert the pipe evenly and straight – without tilting. Push until you feel the resistance of the grip ring and until the fixing ridge reaches the end of the fitting. At the moment when the pipe "passes" through the grip ring, you will feel a slight click or increased resistance – this is correct. Never insert the pipe with a rotating motion.

Step 3: Inserting the second pipe

Repeat the same procedure from the other side. After inserting both pipes, visually check that both fixing ridges are in the correct position. Gently pull the pipes back – if they are correctly inserted, they will not come out.

Step 4: Inspection before covering

Before any covering (inserting into the wall, embedding), pressurize the entire system with a test pressure – more about this in the section on pressure testing below. This is a rule without exceptions.

Installation of T-fittings – branching the distribution

T-fittings are fittings that allow branching of the pipe – either in the same diameter or with a reduction to a smaller diameter for the branch. For wall heating, typical combinations are: main distribution 22 mm with 10 mm branches for individual registers, or 15 mm connections with 10 mm branches.

In the defined range at atria.sk, you will find several key variants:

T-fitting 10 × 10 × 10 – all three inlets the same, for 10 mm diameter distribution (e.g. connecting two registers with a branch)
T-fitting 15 × 10 × 15 – horizontal distribution 15 mm, 10 mm branch for a register
T-fitting 22 × 10 × 22 – main distribution 22 mm, 10 mm branch for a register
T-fitting 22 × 10 × 10 – main inlet 22 mm, both outlets 10 mm

The differences between straight and reduced T-fittings are discussed in more detail in the article Fittings and T-fittings Hepworth: differences between straight and reduced fittings in our Knowledge Centre.

Installation procedure for T-fittings

A T-fitting has three inlet openings. The rule is simple: each opening is physically identical to the openings of a straight fitting for the given diameter. The procedure therefore copies the installation of a straight fitting, but you need to plan the insertion order correctly to have good access to each end.

Recommended insertion order:

First insert the branch (smaller diameter, or the side of the T-fitting) – there is less space for it and access may be difficult later
Then insert the main inlet (one end of the horizontal distribution)
Finally connect the output end of the horizontal distribution

With reduced T-fittings (e.g. 22 × 10 × 22), you always verify which diameter is at which end – this is usually visually clear on the fitting, but during fast installation it can happen that the installer confuses the branch with the main distribution. In that case, you will have to disassemble the joint with a demounting flange, which delays the work and unnecessarily stresses the fitting.

Correct orientation of T-fittings in the system

One of the most common mistakes in practice is incorrect orientation of the T-fitting. This is because the T-fitting has a flow direction: the larger diameter is always the flow-through (the flow continues through it), the smaller diameter is the branch. If you turn the T-fitting upside down (e.g. 10 mm towards the main distribution and 22 mm towards the register), you will create a hydraulically incorrect connection – the regulated flow will be uneven and some registers may not heat up at all.

For wall heating, a simplified rule applies: the larger diameter always points towards the source (boiler, manifold), the smaller diameter always points towards the register. How to design a complete distribution for an entire wall is described in detail in the article How to design a pipe distribution for wall heating using T-fittings.

Pressure testing before covering – the most important step

Without pressure testing, nothing goes into the wall. This is an absolute rule that must not be violated. In practice, we have seen cases where an installer skipped the pressure test in a rush, embedded the wall, and after three months, moisture appeared. Restoring the wall and repairing the leak costs five to ten times more than the installation itself.

Pressure test procedure

For Hepworth push-fit systems in wall heating systems, the following standard values apply:

Test pressure: 1.5 times the maximum operating pressure, at least 6 bar for standard low-energy systems
Test duration: at least 30 minutes at full pressure; we recommend 60 minutes for certainty
Medium: cold water (not air – air pressure testing poses an explosion risk in the event of a rupture)
Inspection: visual inspection of each joint during the entire test period; a pressure drop on the manometer indicates a leak

After a successful test, document the result – date, pressure, test duration and installer's name. This documentation may be important in the event of a warranty claim or insurance incident.

Typical pipe layout configurations in practice

Based on our project experience, we present several typical scenarios that you will encounter most often when installing wall heating systems:

Scenario A: A simple register for one wall

A single register runs the full width of the wall. The supply pipe is 22 mm in diameter (supply and return branch), from which the register branches off in 10 mm diameter. Two T-fittings 22 × 10 × 22 are used to connect the register (one for the supply, one for the return). In the register itself, the 10 mm pipe runs horizontally in a serpentine pattern, connected with straight couplings 10 × 10 where section extension is needed.

Scenario B: Multiple registers in one room (multiple walls)

The main supply pipe 22 mm runs through the room, from which multiple branches lead to individual walls. At each branching point, a T-fitting 22 × 10 × 22 or 22 × 10 × 10 is used (depending on the diameter that continues further). If the supply pipe narrows (after each branch, the flow is smaller), you switch to 15 mm: that is why the range also includes a T-fitting 15 × 10 × 15.

Scenario C: Connecting multiple registers via a secondary 15 mm layout

When the main 22 mm layout is overdimensioned for a small number of registers, a secondary layout in 15 mm diameter is used. You branch off from the main 22 mm layout to 15 mm, and then regularly branch off to 10 mm registers using T-fittings 15 × 10 × 15. This approach saves material and improves hydraulic performance in smaller rooms.

How to elegantly connect pipes of different diameters without losing hydraulic efficiency is described in detail in the article How to correctly connect pipes of different diameters using reduced fittings.

Mounting and routing the pipe in the wall

Hepworth push-fit fittings are rigid, but the pipe in the wall must also be properly supported to avoid stress on the joints caused by expansion. Polybutylene and plastic pipes expand with temperature changes – when moving from 10 °C (installation) to 50 °C (operation), 1 m of pipe will extend by approximately 1–1.5 mm. This is not negligible in a 10-meter layout.

Practical mounting rules:

Clips (hangers) are placed every 500–600 mm for 10 mm diameter, every 700–800 mm for 15 mm diameter, every 1000 mm for 22 mm diameter
Fittings must not be rigidly fixed – the pipe must have space for expansion
At T-fittings and couplings, always place a clip on both sides of the fitting (max. 100–150 mm from the fitting)
At corners and direction changes, use either a bend (Hepworth pipe is flexible up to certain radii) or an angled fitting (elbow)

Disassembly and repair of a joint – what to do if you need to disassemble a joint

If you discover an error before covering – wrong diameter, reversed orientation of the T-fitting, pipe not fully inserted – the joint can be disassembled using a dismount clip. Procedure:

The dismount clip is a flat plastic ring that surrounds the pipe just at the fitting's opening
After inserting the clip, gently push it into the fitting – it will compress the gripping ring and release the pipe
Pull the pipe out evenly without rotating it
After disassembly, check the condition of the O-ring and the inside of the fitting – if the O-ring is damaged, replace the fitting

One customer experience: dismount clips tend to disappear like socks in a washing machine. Always order them in reserve – you will need at least 2–3 pieces for each diameter you work with. Without them, repairing a faulty joint is extremely time-consuming.

Inspection of the entire layout after installation is completed

Before final covering, perform a systematic inspection of the entire layout according to the following checklist:

✔ Every joint visually: fixing mark in the correct place (pipe fully inserted)
✔ Correct orientation of each T-fitting (larger diameter towards the source)
✔ Clips in the correct positions, fittings not mechanically stressed
✔ Pipe is not bent sharply below the minimum bending radius (for DN10: min. 100 mm, for DN15: min. 150 mm)
✔ Pressure test has been carried out and the result is documented
✔ The system has been flushed before the first filling (to remove sludge and impurities)

If you encounter typical errors, causes of leaks or solutions to problems after installation, these are discussed in detail in the articles Common errors when installing T-fittings and couplings for wall heating and Causes and solutions for leaks at Hepworth fitting joints.

Special situations during installation: what to do when the standard procedure cannot be used

In practice, we often encounter situations that are not covered by standard instructions. A few examples:

Limited space when inserting the pipe

When working in a narrow groove in the wall or behind existing pipes, the standard method of inserting "pipe into fitting" may be physically impossible. Solution: insert the fitting onto the pipe (not the other way around) – the push-fit system allows this, and the joint functions the same. You just need enough space to slide the fitting along the pipe to the correct position.

Repairing an existing layout without draining the entire system

If you need to replace one fitting in an existing layout without the possibility of draining the entire system, a combination of shut-off push-fit valves and a dismount clip is used. Do not attempt this without knowledge of the entire layout and without a replacement fitting prepared – the procedure requires an experienced installer.

Transition between different materials (e.g. Cu → Hepworth)

For transition from copper pipes to Hepworth pipe, transition fittings (Cu × push-fit) are used. These fittings have a thread or compression side for copper on one side, and a push-fit side for Hepworth on the other. Never connect copper and plastic directly without a transition fitting – expansion is different and chemical compatibility must be verified.

Most frequently asked questions (FAQ)

Do I need to use any lubricant or sealing compound for Hepworth push-fit fittings?

No, Hepworth push-fit fittings are designed for dry insertion – the O-ring is already pre-lubricated by the manufacturer. Using additional lubricant (e.g. vaseline) may slightly ease insertion, but with some types of lubricants, there is a risk of damaging the NBR or EPDM rubber O-ring. Never use mineral oils or synthetic lubricants without verifying compatibility with the sealing material. It is usually fine to slightly moisten the end of the pipe with water, which can help in difficult insertions.

Can I reuse Hepworth fittings after disassembly?

Fittings can generally be reused after one disassembly if the O-ring is in perfect condition and the grip ring is not deformed. In practice, however, we recommend visually inspecting the fitting after each disassembly and replacing it if there is any doubt – the cost of a new fitting is negligible compared to the cost of repairing a leak in the wall. Never reuse a fitting where the O-ring is visibly damaged.

What depth of groove in the wall do I need for pipe with Hepworth fittings?

The groove must be deep enough to fully accommodate the pipe and fitting and not protrude above the level of the future plaster. For DN10 pipe with a fitting, the minimum groove depth is 35–40 mm, for DN15 about 45 mm, for DN22 about 55 mm. The width of the groove must be at least 20 mm larger than the outer diameter of the fitting to allow the pipe to be laid and fixed without stress. At T-fittings and couplings, allow for a wider groove – T-fittings take up space to the sides.

What if the grip ring engages before the pipe is fully inserted?

This can happen if the pipe is inserted crooked or with too much force in the wrong direction – the grip ring can lock prematurely. Solution: use a dismount clip, disassemble the joint and start again. Never try to force the pipe in – you may damage the O-ring or deform the grip ring, which can cause a leak. Also check that the pipe has a properly beveled edge – an un-beveled edge is the most common cause of this problem.

Is it possible to install Hepworth fittings at negative temperatures?

Installation at temperatures below 0 °C is technically possible, but significantly more complicated. Plastic becomes more brittle at freezing temperatures and the grip ring behaves differently. The manufacturer generally recommends installation at temperatures between +5 °C and +35 °C. If you have to install in winter, ensure that the working area is heated to at least +5 °C, place the pipe and fittings in a heated area for at least an hour before installation, and perform the pressure test with water at a temperature of at least +10 °C to prevent freezing during the test.

How long can the pressure test be acceptable for commissioning and insurance?

Requirements vary according to country, insurance company and specific standard. In Slovakia, reference is made to STN EN 14336 (installation of heating systems) and STN EN 12828 for heating systems. Typically, a pressure test at 1.5 times the maximum working pressure, but at least 6 bar, for a duration of 30–60 minutes with a documented record is required. Always verify the specific requirements with your designer, inspection technician and insurance company – these documents may be required in the event of an insurance claim.

Conclusion: installation of Hepworth fittings is a craft, not improvisation

The Hepworth push-fit system is excellent precisely because it does not require special skills or expensive tools when the correct procedure is followed. The key is diligence in each step: proper pipe preparation, checking the insertion depth, pressure testing before covering and documentation. The fittings themselves are reliable – problems arise almost exclusively from carelessness during installation.

If you want to learn more about the correct selection of fittings for a specific project, about the maintenance of piping systems or about solving problems after years of operation, we recommend the articles Maintenance and inspection of wall heating piping systems with Hepworth fittings and Common questions about Hepworth fittings for wall heating in our Knowledge Centre. The full range of fittings for wall heating can be found in the category wall heating and heating.

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.