Copper pipe brazing - selection and installation
Crimp fitting for copper pipe – introduction to the topic
If you are working with copper pipe in heating, plumbing or solar systems, you will sooner or later encounter a situation where you need to connect the pipe to a fitting, elbow, valve or other component without the need for soldering. This is exactly what a crimp fitting is for – at first glance a simple, yet highly functional and reliable connection that has a fixed place in professional installation. In this article, we will take a closer look at the entire issue: what a crimp fitting actually is, how it works, how to choose it correctly for copper pipe and how to install it so that the connection lasts many years without leaks.
Crimp (compression) fittings are not a novelty – they have been used for decades and bring with them several key advantages over soldered or pressed connections. They do not require an open flame, special tools or special qualifications with a certificate. Despite this, there are many details that determine whether the connection will be tight and durable or whether it will show signs of leakage after a short time. It is therefore important to understand not only "how", but also "why" – and this is exactly the goal of this text.
What is a crimp fitting and how does it work
A crimp fitting (also called a compression fitting or olive fitting) is a mechanical connection that creates a tight seal on a pipe without any gluing, soldering or pressing. It consists of three basic components: the fitting body, a vertical nut and a crimp ring – the so-called olive. The principle is simple: when the nut is tightened, the olive plastically deforms and firmly presses against the outer surface of the pipe, thus creating a hermetic seal.
This principle works so reliably precisely because the copper pipe has a defined outer geometry and relatively soft surface into which the olive slightly embeds when tightened. The result is a connection that can withstand normal pressures in heating (typically 6 to 10 bar), is not sensitive to vibrations and can be disassembled and reused if necessary – of course with a new olive, since the original one is permanently deformed during the initial tightening.
In the world of heating and plumbing installations, there are two basic types of crimp fittings: single (single ferrule) and double (double ferrule). For copper pipe in residential heating installations, the type with one olive is commonly used, which fully meets the pressure and temperature requirements of standard systems. The double olive is used more in industry or at higher pressures.
Standards, materials and labeling – what you need to know before purchasing
Before you order a crimp fitting, it is important to understand what you are actually buying. The market offers a huge number of products of different quality and origin, and not every "crimp fitting for 15 mm pipe" is the same. The difference can be in the material of the body, the material of the olive, the manufacturing tolerance and the maximum operating parameters.
For copper pipe in heating systems, the body of the fitting is usually made of brass (CuZn) or chrome-plated brass. The olive is usually made of soft brass or copper, which ensures compatibility with the copper pipe – galvanic corrosion does not occur. Some products have an olive made of stainless steel, which is acceptable, but when used with a copper pipe, the contact between copper and steel can be problematic in certain environments (acidic water, aggressive medium) in the long term. Always check, for which medium the fitting is certified.
As for the product labeling, when selecting, you will encounter a combination of numbers and letters such as 15×1 EK. This labeling means: the pipe diameter is 15 mm, the wall thickness is 1 mm, and EK (Einrohr-Kompression or European Kompression) indicates the European standard for compression fittings. Specifically for the Hepworth system, it is important: Crimp fitting - for copper pipe - 15x1-EK is designed specifically for copper pipes with an outer diameter of 15 mm and a wall thickness of 1 mm, which is the most common dimension of copper pipe in domestic heating in Slovakia.
There is also Crimp fitting 15 x 1 EK for copper or PB pipe, which is constructed to work with polybutylene (PB) pipe of the same outer diameter. This is an important detail – if you have a combination of materials in the building, you can use one type of fitting, which simplifies logistics and inventory on the warehouse.
Choosing the correct compression fitting – dimensions, pressure, temperature
Pipe diameter and wall thickness
The first and most important parameter when choosing a fitting is the outer diameter of the pipe. Copper pipes are most commonly used in heating in sizes 15×1 mm and 18×1 mm – the number before the slash is the outer diameter in millimeters, the number after the slash is the wall thickness. In Slovakia and the Czech Republic, it is standard that the supply from the boiler to the manifold, or the horizontal piping along the floor, is implemented in 18 mm, while the branches to the radiators are usually in 15 mm. For each of these dimensions, there is a corresponding compression fitting – they are not interchangeable.
If you are unsure about the dimensions, do not estimate visually – measure the outer diameter with a caliper. Confusion between 15 mm and 18 mm is excluded, as the difference in diameter is significant enough. However, there may be slight tolerance deviations between different manufacturers, which can affect the quality of the joint. Therefore, it is important to purchase fittings from verified sources with declared tolerances.
Operating pressure and temperature
For standard heating (low-temperature or high-temperature), standard compression fittings for copper pipes are dimensioned at a minimum of 10 bar at temperatures up to 110 °C. Most high-quality brass fittings can withstand higher pressure – in manufacturer catalogs you will find values of 16, sometimes 25 bar (PN16, PN25). In solar systems, where the medium temperature can briefly exceed 150 °C, it is recommended to verify the temperature resistance of the specific product and, if necessary, choose a fitting with a PTFE (Teflon) olive or with high-temperature certification.
It is also important to remember that due to the thermal expansion of the pipe (copper pipe expands by approximately 0.85 mm per meter when heated by 50 °C), the joint can be mechanically stressed. Proper securing of the pipe using clamps and hangers – as described in the article Clamps vs. hangers for pipe support – when to use which – significantly reduces the risk that thermal expansion will load the joints.
Thread on the other side of the fitting
A compression fitting typically connects the pipe to a valve, so it has a compression mechanism (olive + nut) on one side and a thread – either external (AG) or internal (IG) – on the other side. The most commonly used threads are G 1/2" and G 3/4" (BSP/Whitworth). Always check what thread your valve has before purchasing and buy the corresponding fitting. Other combinations (e.g. metric threads M22×1.5) also appear when connecting to meters or special valves.
The Hepworth system and its specifications for compression fittings
Hepworth (Wavin Hep2O, or the Hepworth system) is a British piping and fitting system with a long history on the European market and in recent years it has been gaining an increasingly firm position on the Slovak market, mainly due to its flexibility and availability of components. The Hepworth system covers not only plastic (polybutylene) piping, but within the range of assembly tools it also includes elements that are compatible with copper piping – including compression fittings.
The reason is practical: in practice, we often encounter situations where existing copper piping needs to be extended or connected to new plastic parts of the system. Hepworth anticipates this and offers adapters and compression fittings designed to work with both materials. Specifically, the Compression Fitting 15 x 1 EK for copper or PB pipe is a typical example – one component, two applications, proven quality of a system solution.
Installation of a compression fitting on copper pipe – step by step
Preparing the pipe
The quality of the joint starts with the preparation of the pipe itself. The copper pipe must be cut perpendicularly – any angle or unevenness of the cut will cause the olive to not seat evenly and the joint may be leaky. A special pipe cutter (a saw or a rotating cutter) is best for this, which automatically ensures a perpendicular cut. Using a regular metal saw is possible, but it requires greater care in the final finishing.
After cutting, all burrs must be removed – both from the inside and the outside of the pipe. Inside, a rounded file or special deburring tool helps, while on the outside a fine file or sandpaper is sufficient. The outer edge of the pipe must be smooth and free of burrs, as the olive rests on it. Any scratches or rough burrs can damage the sealing.
Copper pipe should be clean and dry. If the pipe is selected from an existing installation, check whether it is corroded or deformed – such a pipe is not suitable for use with compression fittings. Also check whether the outer diameter of the pipe corresponds to the nominal size – low-cost imported pipes may have deviations.
Correct order of components
One of the most common mistakes when installing compression fittings is the incorrect order of component installation. Before inserting the tube into the body of the fitting, you must slide the components onto the tube in the correct order: first the nut (with the threaded side facing away from the end of the tube), then the olive. If you forget to slide the nut and olive on beforehand, the joint cannot be completed without disassembling the entire connection.
The olive always has a defined side – usually the narrow, slightly conical side faces the body of the fitting, while the rounded side is oriented towards the nut. For symmetrical olives (some types), the order does not matter, but for asymmetrical olives, follow the orientation according to the manufacturer. Incorrect orientation of the olive can reduce the tightness of the joint or cause its rapid failure.
Tightening the nut – the golden rule of 1¼ turns
After sliding on the nut and olive, insert the tube into the body of the fitting until it reaches the stop – the insertion depth is usually visible or can be felt. Then manually tighten the nut until it is firm. At this point, the tube must not move freely, but the nut is not yet sealed. Now comes the wrench: the standard procedure is to tighten the nut an additional 1 and a quarter turns (i.e., 360° + 90°). Some manufacturers recommend 1 to 1.5 turns – it depends on the material and design of the olive.
This rule is intuitive for an experienced plumber, but for a beginner it may be difficult to understand. The principle is as follows: the first turn pushes the olive into contact with the conical seat in the body of the fitting, and an additional quarter turn plastically deforms the olive so that it tightly wraps the tube and creates a seal. If tightening is stopped too early, the olive is not sufficiently compressed and the joint will be leaky. Conversely, over-tightening deforms the olive too much and you risk cracking it, or possibly damaging the threads.
Always use two wrenches when tightening – one holds the body of the fitting (for example, a valve), the other tightens the nut. Never turn the body itself, as you might rotate the valve or piping system, which can damage other joints in the line.
Inspection and pressure test
After completing the installation, always perform a visual inspection of the joint: the nut must be properly tightened, the tube must be properly inserted, and the olive must not be visible outside the body of the fitting. Before filling the system to full pressure, we recommend a pressure test – typically 1.5 times the operating pressure for at least 30 minutes. In practice, for residential heating, a pressure of 6 bar is used with a test pressure of 9 bar.
If the joint leaks, DO NOT try to tighten it further under full pressure or with running water – first depressurize the system, drain it, and inspect the joint. The cause may be incorrect orientation of the olive, dirt on the surface of the tube, or a damaged olive. In such cases, the correct solution is to disassemble the joint, replace the olive (never use the same olive when re-tightening!), and repeat the installation. Further information on the causes of leaks can be found in the article Loose or cracked joints – causes and solutions.
Securing copper pipe with compression fittings – brackets and clamps
A compression fitting is not only about the joint itself – equally important is the correct securing of the pipe along the route. Copper pipe with compression fittings must be supported so that mechanical stress on the joints caused by the weight of the pipe, thermal expansion, or external vibrations is eliminated. For this purpose, mounting brackets and clamps are used.
For 15 mm copper pipe, the suitable Pipe bracket, 16 mm is dimensioned for pipes with an outer diameter of approximately 16 mm – that is, directly for a 15×1 mm copper tube (outer diameter is 15 mm, but the bracket needs a slight clearance for convenient mounting). For installations where both dimensions – 15 mm and 18 mm – are present in the route, the suitable Pipe brackets, 16–18 mm cover both sizes and simplify installation.
The spacing of the securing points depends on the diameter and material of the pipe. For 15 mm copper pipe, the approximate rule is: horizontal routing – every 1.2 to 1.5 m, vertical routing – every 2 m. At higher temperatures (e.g., when directly connected to a boiler), we recommend reducing the spacing to 0.8–1 m to minimize sagging. Compression fittings must always be placed so that the joint is accessible for possible inspection or repair – never embed them without a maintenance access point.
For mounting brackets into the wall or ceiling, special anchoring screws are used. In the category of installation tools, you can find for example the M8 KOMBI screw, which is suitable for mounting brackets and supports in various types of substrates. The correct choice of anchoring element depends on the wall material – different for concrete, aerated concrete, and drywall. More on this topic can be found in the article How to properly mount clamps and brackets for piping.
Typical mistakes when installing compression fittings – from practice
Over the years of practice in heating system installation, we see the same mistakes that lead to problems. We mention them not to scare anyone, but because knowing them is the best prevention.
Mistake No. 1: Forgetting the nut before sliding on the olive. This happens almost inevitably to an inexperienced plumber on the first or second job. The tube is inserted into the body, the olive is slid on, but the nut is forgotten. Result: the joint cannot be completed, everything has to be disassembled. Solution: always prepare all components in the correct order on the tube before inserting it into the body at the beginning of the installation.
Error No. 2: Reusing the same olive. Some people try to save money by reusing an old olive after disassembling a joint. This is a critical mistake – the olive plastically deforms during the first tightening and it is not possible to achieve the same sealing effect on the second use. Always use a new olive for every assembly.
Error No. 3: An untightened joint – the feeling that "it holds anyway". Visually skipping the tightening with a wrench leads to the joint holding at low pressures, but during a pressure test or during the first operation, it will start to leak. Always make sure you have followed the rule of 1¼ turns with the wrench after manual tightening.
Error No. 4: Using sealing tape (PTFE) on the olive. Some plumbers, out of precaution, wrap the olive with PTFE tape or apply sealant. This is unnecessary and counterproductive – a properly tightened olive is itself a sealing element, and an additional seal interferes with the correct seating of the olive and can actually worsen the seal. PTFE is suitable only for threads – not for olives.
Error No. 5: Using the wrong type of olive for the pipe material. A copper pipe olive is not automatically suitable for plastic PB or stainless steel pipe. Each material has different mechanical properties and tolerances. If you need a joint between copper and PB, use an olive explicitly certified for both materials, such as Zverné šróbenie 15 x 1 EK na medené alebo PB potrubie from the Hepworth system.
Error No. 6: A joint in an inaccessible location without a maintenance opening. A compression joint is a removable joint and its advantage is precisely the possibility of inspection and repair. If you embed it or cover it with drywall without a maintenance opening, you lose this advantage and in case of a leak, you will have to break it open. Always plan the route so that each joint is accessible.
Compression joints vs. other types of joints – practical comparison
In the decision-making process of whether to use a compression joint or another type of joint, several factors play a role. Let's take a brief practical comparison:
- Soldering (capillary joint): The most durable and mechanically robust solution. It requires an open flame, additional material (solder), flux, and qualification. It is unsuitable where there is a fire risk, near flammable materials, or if you do not have the appropriate tools. In a finished installation where a pipe needs to be cut and a new component inserted, soldering is more time-consuming and cumbersome than a compression joint.
- Press fittings: A modern alternative without flame, but it requires special pressing pliers (price 500–2000 €), which not every plumber has. The joint is non-removable and very reliable. For large projects with repeated joints, press fitting is more economical, but for small repairs or individual connections, a compression joint is a more flexible option.
- Compression joints: Do not require special tools or flame. Removable, repairable, quick assembly. Ideal for connecting fittings (valves, meters, manifolds), repairs, adding to existing systems, or places where soldering is not suitable. It requires care during assembly and regular checks in the first years of operation.
In practice, these methods do not exclude each other – an experienced plumber combines them according to the situation. Long straight pipe sections can be solved by soldering or press fitting, while connections to fittings and take-off points are solved by compression joints for their removability.
Material compatibility and galvanic corrosion – what not to forget
Copper pipe in contact with another metal can, under certain conditions, create a galvanic cell that accelerates the corrosion of the weaker metal. This is a topic that is often underestimated in practice. Basic rule: copper pipe must not be in direct hydraulic contact with steel pipe, because copper ions (Cu2+) penetrate into the water and settle on the steel, accelerating its corrosion. Brass fittings (CuZn) are fully compatible with copper from a galvanic perspective.
If you have to connect copper and steel parts (which is common in renovations), use a dielectric union (insulated joint), which breaks the electrical conductivity between the metals. This is not an unnecessary precaution – without a dielectric union, steel parts in the system can corrode significantly faster, which is especially noticeable on steel heating bodies.
Frequently asked questions (FAQ)
Can I use a compression joint in underfloor heating where the pipe is in the screed?
In general, compression joints are not recommended in the screed – not because they are unreliable, but because you would lose access to the joints in case of inspection. In underfloor heating, either full-length pipe loops (a single piece of pipe) are preferred, or in the case of a necessary joint, the use of a press fitting or soldered joint with a special protective sleeve. If you must have a joint in the structure, ensure a maintenance shaft. For pipe runs above the floor or in an accessible trench, a compression joint is fully acceptable.
What wrench should I use for tightening? Must it be a torque wrench?
A torque wrench is not mandatory – most plumbers work with standard open-end or box wrenches. More important than the absolute value of torque is following the rule of 1¼ turns after manual tightening. For G 1/2" fittings with an olive on Cu 15 mm, tightening ranges between 20–30 Nm, which is easily achievable with a standard wrench without excessive force. A torque wrench is useful in mass production or in controlled environments (industry, solar systems with certification), where torque tightening must be documented.
What to do if the joint still leaks after tightening?
Do not try to tighten it further – over-tightening will not improve the situation, it will rather worsen it. The correct procedure: depressurize the system and drain the water from the affected section. Disassemble the joint, check the olive (whether it is cracked, unevenly deformed, or incorrectly oriented), check the pipe surface (scratches, burrs, ovality). Always replace the olive with a new one. Also check the seating surface in the fitting body – if it is damaged, the entire fitting must be replaced. Carefully repeat the cut and preparation of the pipe and reassemble. In most cases, the leakage problem stems from insufficient pipe preparation or a faulty olive.
Can I use a compression joint for potable water?
Yes, but you must ensure that the specific product is certified for potable water (DVGW, KTW, WRAS or other valid certifications for your market). Brass fittings without potable water certification may contain lead, which can migrate into the water and is harmful to health. Always require a certificate of product certification for potable water. The Hepworth system on atria.sk is primarily oriented for heating, so when using it for potable water, always check the specifications of the specific product.
How many compression joints can I place in a row on one pipe run?
There is no technical limit to the number of fittings in a run, but from a practical point of view: each fitting is a potential leak point and adds hydraulic resistance (although negligible). From a reliability standpoint, it is always better to minimize the number of joints in a run and use fittings only where necessary – for example, when connecting fittings or when transitioning between materials. More on route planning can be found in the article How to choose the right installation tools for Hepworth piping.
What is the difference between a compression fitting and a press fitting in terms of cost?
A compression fitting is in most cases cheaper than a press fitting of the same size and function. However, when comparing the total cost of a project, you must consider that press fitting requires an investment in pressing pliers (hundreds to thousands of euros), while for compression fittings a standard wrench is sufficient. For smaller projects (family homes, apartments), a compression fitting is the more economically advantageous option. For large projects with dozens or hundreds of joints, the investment in pressing tools usually pays off in labor savings. More on choosing the right method can also be found in the article Manual vs. mechanical pipe clamping – differences and use.
Conclusion – Compression fittings as a reliable assistant in heating
Compression fittings for copper pipe are a proven, practical, and universally applicable component of every heating installation. If you understand their principle, choose the correct size, and follow the installation procedure, you can be sure that the joint will last for many years without any intervention. The key points that every reader of this text should remember: check the outer diameter and wall thickness of the pipe, use the correct type of fitting (for Cu or for Cu and PB), carefully cut and deburr the pipe, slide on the nut and olive in the correct order, tighten by exactly 1¼ turns with a wrench, and perform a pressure test. Every joint must remain accessible for possible inspection.
Proper installation also begins with good pipe fixing – therefore, do not forget to use brackets and clamps with appropriate spacing to protect the joints from mechanical stress. A complete range of installation tools for the Hepworth system can be found in the category installation tools, where you can choose everything you need for a professional installation – from compression fittings through brackets and clamps to anchor screws.
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