Press fittings vs. threaded fittings: when to use which solution
Press fittings vs. threaded fittings: when to use which solution
One of the most common questions we deal with during the design and implementation of professional heating systems is: "Should I use a press fitting or a classic threaded connection?" At first glance, it seems like a simple technical choice, but in practice, the correct answer depends on a whole range of factors – from the type of installation and operating conditions to the availability of tools and long-term maintenance costs. In this article, we will thoroughly examine the issue, with specific numbers, examples from practical experience, and clear recommendations for different types of situations.
Basic differences between press fittings and threaded fittings
Before we start comparing, it is useful to recap what each of these systems actually is and on what principle it works.
Threaded fittings – proven tradition with a focus on sealing
Threaded fittings have been present in heating for literally decades. The principle is simple: an internal or external thread of the fitting is screwed onto a thread on the pipe or fitting, with the seal achieved by a combination of conical or cylindrical thread and sealing material – most often PTFE tape, hemp gasket with paste, or chemical sealant. In professional heating, the British pipe thread BSP (G/Rp) according to the ISO 228 and DIN 259 standards is mainly used.
Cylindrical internal thread Rp and external thread R are most common in heating systems. Rp 1/2", Rp 3/4", R 1" – these designations are known to every installer. Fittings with cylindrical threads seal mainly by the sealing material itself, not by the geometry of the thread, so the correct application of the sealing material is critical.
Press fittings – a modern alternative without fire and thread
Press fittings (crimped fittings) represent a technology where the connection is created by mechanical crimping with special pliers or hydraulic crimping directly onto the pipe. A sealing O-ring placed in the groove of the fitting is deformed during crimping and creates a permanent, watertight connection. For steel pipes in heating, press fittings with EPDM or NBR sealing are most commonly used, depending on the medium.
Key property of press fittings: the connection is either correctly crimped and sealed or visibly faulty even before the system is pressurized – so-called "wet installed" principle (an incorrectly crimped fitting will leak water immediately upon filling). This is a crucial safety advantage over threaded connections, where a poor seal may only become apparent after years of operation.
Where press fittings clearly lead
Speed of installation and work productivity
In terms of pure installation speed, press fittings are unmatched. In practice, I have had the opportunity to observe how an experienced installer can create 30–40 connections per hour with a crimping tool. The same number of properly sealed threaded connections – with winding sealing material, a wrench, and the correct tightening torque – takes about half as long again. In large installations (e.g., apartment buildings, industrial halls, hotels), this difference in productivity translates into thousands of euros saved on labor.
In addition, there is no need for drying the sealing material. With threaded connections using chemical sealant (e.g., Loctite 577 or similar), the installer must wait for the sealant to cure – typically 30 minutes to several hours before the system can be loaded. A press connection is functional immediately after crimping.
Safety in areas without open flame
This is an argument that often decides in practice. Press fittings do not require soldering, welding, or any other source of heat. For installations in residential cores, areas with flammable materials, facilities with explosion hazards, or areas with strict fire regulations, press fittings are either strongly preferred or directly prescribed. Health risks from soldering (vapors from flux, metal aerosols) are also eliminated.
Minimal requirements for operator qualification
Soldering or welding of steel piping requires a certified welder or a skilled solderer. A press fitting can be handled by any experienced installer after a short training session, who learns the correct technique for inserting the pipe and operating the crimping tool. Of course, basic rules must be followed – especially correct pipe insertion, cleanliness of the joint, and checking the correct seating of the O-ring – but the overall learning curve is much shorter.
Simple embedding and installation in enclosed spaces
Threaded connections require space for turning the wrench – at least 10–15 cm of free space around the fitting. Press tools can work in tighter spaces, which you will appreciate, for example, when embedding conduits in a suspended ceiling, in technical shafts, or when working with pre-prepared piping installed right next to the wall.
Where threaded fittings have an irreplaceable role
Connecting to valves and devices with BSP threads
This is an absolute dependency: valves, pumps, distributors, pressure gauges, safety valves, expansion vessels, boilers – practically every device in professional heating has threaded connection ports. The BSP thread (Rp 1/2", Rp 3/4", R 1") is the de facto industrial standard for fittings. For these connections, you must use a threaded connection or a combined press-threaded fitting (so-called connecting coupling).
Exactly here, connecting couplings with internal threads come into play, elegantly solving the transition between the press pipe system and the threaded ports of fittings. On one side you have a press end (which is crimped onto the pipe), and on the other side an internal Rp thread – for example, connecting coupling 15 mm × Rp 3/4" or 18 mm × Rp 1/2" for larger diameters. More about the correct selection of diameter and thread combination can be read in the separate article How to choose the correct combination of pipe diameter and fitting thread in our Knowledge Center.
Repair and inspection of existing threaded pipe systems
When performing service work on old steel pipe systems (usually from before the year 2000), it is a purely threaded installation. While it is technically possible to repair such systems with press fittings, in practice you will encounter a problem: press fittings are dimensioned according to the outer diameter of the pipe according to EN standards, while older pipe systems may have different exact dimensions or a surface altered by corrosion. A classic threaded repair is faster, cheaper, and more reliable in such cases.
Economics for small jobs and repairs
Press tools cost thousands of euros – professional hydraulic crimping tools range from 800 to 3,000 €, and electric ones from 1,500 to 5,000 €. For a one-time repair of three fittings or for a small job in a family home, purchasing such tools is economically senseless. A threaded fitting, a pipe wrench, and teflon – these are what every installer has in their car.
Of course, tools can be rented, but even here, for small jobs, a classic threaded connection is a more logistically simple option. The break-even point occurs roughly at jobs with 50 or more connections, where the time saved with press fittings compensates for the tool costs (or rental costs).
Accessibility and repairability
Threaded fittings can be disassembled, modified, and reassembled. A press fitting is permanent after crimping – when disassembling, the pipe must be cut and a new fitting installed. In places where future modifications to the pipe system are expected or where regular disconnection of fittings (e.g., for service) is necessary, a threaded coupling is advantageous, as it allows for easy disassembly without losing the pipe.
Pressure and temperature resistance: what the technology says
Both systems cope with standard operating conditions in heating installations, but it is good to know the specific limits.
Press fittings for steel pipe
Standard press fittings for steel pipe with EPDM sealing are certified for:
- Maximum operating pressure: 16 bar (sufficient for most central heating systems, standard operating pressure is 1.5–3 bar)
- Maximum medium temperature: 120 °C (EPDM) – suitable for low-temperature and classic heating
- For higher temperatures (steam systems above 120 °C), it is necessary to use press fittings with HNBR sealing
Threaded fittings made of steel or spheroidal graphite cast iron (GGG) do not have any material-related issues even at 150 °C and higher pressures – the limiting factor is then rather the quality of the sealing and its temperature resistance. Teflon tape can withstand up to 260 °C, hemp sealing with paste up to 130–150 °C, chemical sealants (anaerobic) typically up to 150 °C.
Question of service life
Properly crimped press joints have a service life comparable to that of the pipe itself – for steel pipe in closed heating systems, this can be 30–50 years. A critical component is the O-ring: EPDM has excellent resistance to aging, but it must not come into contact with mineral oils or certain corrosion inhibitors incompatible with EPDM.
Threaded joints with hemp sealing were once the standard even for 40-year-old pipe systems. Their weakness is that hemp can dry out over time (especially during long periods without water) or biologically degrade. Modern synthetic sealants have a longer service life, but are more prone to mechanical damage during reassembly.
Combined solutions: press pipe + threaded connection of fittings
The most sensible approach in professional installations – and the one that has become the de facto standard in practice – is a combination of both systems. Main lines are built with press fittings (speed, safety, tightness), while at each point of connection of a valve, pump, or other fitting, a combined fitting with a threaded end is used.
An example is a connecting coupling 18 mm × Rp 3/4" – the press end is crimped onto a steel pipe DN18, the threaded end Rp 3/4" is screwed into the fitting. A very common combination is also 22 mm × Rp 1" for connecting circulation pumps, balancing valves, and collectors to larger pipe diameters.
This combined solution combines the best of both worlds: a fast and reliable main installation with the press system and a flexible, serviceable fitting zone with threaded connections. We will discuss this topic in more detail in the article Connecting couplings with internal thread: how to properly connect pipe to fitting.
Practical scenarios from everyday contract practice
Scenario 1: New apartment building with 30 apartment units
This is an ideal scenario for press fittings. Hundreds of joints on risers and distribution lines in apartment cores, work in tight conditions, demand for speed, no fire near gypsum board and thermal insulation. The press system can save up to 20–30 % of the total installation time here. Combined connecting couplings are then used at each apartment branch and when connecting to heating units.
Scenario 2: Single-family house – boiler and radiator replacement
A job in the range of 15–20 joints in an existing threaded pipe system. Most experienced installers will reach for a threaded solution here – there is no sense in the cost of renting press tools, and if the pipe is older and has varied dimensions, press fittings could run into problems with tolerances. An exception is if the installer has their own press tools and the job is part of a more complex project in the house.
Scenario 3: Technological boiler room in an industrial building
Larger diameters (DN 22, DN 28 and above), higher pressures, specific media. Here it depends on the specific conditions: with standard heat transfer media (water with an inhibitor compatible with EPDM), press fittings are fully suitable. For steam distribution, systems with oil or temperatures above 120 °C, a safer choice is welding or threaded connections with HNBR/FKM sealing.
Scenario 4: Service – replacement of a cracked radiator valve
Classic case: a customer comes with a leaking valve in the living room, only the valve needs to be replaced. The distribution is a threaded system from the 90s. Answer: threaded valve, Teflon, done in half an hour. Installing a press solution here would be technically possible, but time- and cost-inefficient.
Standards, certificates and regulations
Both systems must comply with current European standards. For press fittings in carbon steel, the key standard is EN 10305-3 (precision tubes) or EN 10255 for threaded steel tubes. Press fittings for heating and sanitation must be certified according to EN ISO 9001 and the manufacturer must declare conformity with DVGW W 534 (Germany) or an equivalent EN standard for sealing technology.
Threaded fittings for heating are governed by EN 10241 (carbon steel fittings), or EN 1561 for cast iron fittings. Threads are governed by ISO 7-1 (Rc/Rp conical) and ISO 228-1 (G/Rp cylindrical).
Important note for designers: in some project conditions (e.g. insurance-mandated conditions, special investor requirements), the type of joint may be explicitly prescribed. Always check the project and technical specification before starting the job.
Economic calculation: what is cheaper?
A comparison of the pure price of fittings shows that press fittings are generally 30–60 % more expensive than equivalent threaded fittings of the same diameter. At first glance, this is an argument in favor of threaded fittings. But total job costs are a different matter:
- Labour cost: With a press system, you save 30–50 % of installation time, which with an hourly rate of 20–35 €/h quickly offsets the cost of the fittings
- Seals and consumables: Teflon, hemp, paste – on a large job, this is not a negligible item
- Complaints and warranty repairs: Statistically, press joints have significantly lower failure rates than threaded joints dependent on the quality of manual sealing. One warranty repair for a leaking threaded joint in a ceiling void can cost more than the savings on fittings for the entire job
- Tools: If you own them, a press system is economically viable from about 50 joints upwards; if you rent them, the threshold is higher
Most frequently asked questions (FAQ)
Can I combine press and threaded fittings in one system?
Yes, and in practice this is a common standard. Main distribution lines can be solved with press fittings, while each connection to equipment (valve, pump, manifold, boiler) uses a combined connection with a press end on the pipe side and a threaded end on the equipment side. Just make sure not to mix two different press systems from different manufacturers in one joint – the groove profiles for the O-ring may not be compatible.
Can I disassemble and reuse a press fitting elsewhere?
No. After pressing, a press fitting is permanent and cannot be disassembled without damage. For repairs, it is necessary to cut the pipe at the fitting location and install a new fitting. For this reason, in places where future disconnection is expected (e.g. service points), it is reasonable to leave sufficient pipe length or use a threaded connection with a removable nut.
What tools do I need for press fittings and where can I get them?
You need a press tool – mechanical (for smaller diameters, cheaper, but physically demanding), electric (more convenient, suitable for regular work), or hydraulic (for large diameters and intensive use). The appropriate jaws in the correct profiles (M, TH, U, V – depends on the manufacturer of the fittings) are needed. You can buy the tools from heating technology distributors or rent them from specialized tool rental services – typically for 15–40 €/day.
Are press fittings suitable for refrigeration or air conditioning systems?
For refrigerant (freon) in air conditioning, press fittings intended for heating are not suitable – these systems require brazed or welded joints of special copper tubes. For refrigeration systems with brine or glycol mixtures, the use of press fittings is possible, but the compatibility of the O-ring with the given medium must be verified – EPDM is not suitable for all glycol mixtures, NBR has other limitations.
What is the difference between a press fitting and a push-fit fitting?
A press fitting (crimped) requires special crimping tools – the joint is created by mechanically deforming the fitting around the tube. A push-fit (snap-on) fitting is installed manually without tools – the tube is simply pushed into the fitting, where it is held by a steel ring with teeth and an O-ring seal. Push-fit fittings are faster to install, but their use is limited to lower pressures and temperatures (usually max. 10 bar / 95 °C) and are not suitable for embedded systems without inspection hatches.
Can I use press fittings for outdoor or underground lines?
Steel press fittings for heating are primarily intended for indoor distribution. For outdoor or underground lines, corrosion protection is necessary – either a special insulation sleeve (for press fittings, insulation sleeves are available), or the choice of a more suitable material (e.g. copper with good insulation, pre-insulated pipe). Corrosion is a critical issue for steel pipes in an outdoor environment – we will address this topic in more detail in the article Corrosion of steel pipes and fittings: causes, prevention and solutions.
Conclusion: the right choice depends on the context, not on fashion trends
Press fittings are today the dominant technology for new professional installations, and for good reasons: speed, safety, reliability and traceability of the joint. Threaded fittings remain and will remain irreplaceable wherever it is about connecting to equipment with threaded nozzles, for service work on old systems, for small jobs without your own press tools, or wherever you need a dismountable joint.
An experienced installer and designer does not swear by one system – they know when to use the press tools, when to reach for the wrenches, and most importantly, they know where to use combined connection fittings that elegantly combine both worlds. If you want to dive deeper into the topic of dimensions and markings, we recommend reading the articles Steel pipe and fitting sizes: which dimension do I need for my system and How to correctly install a press fitting on a steel pipe without leakage in our Knowledge Center.
The right combination of both technologies – press distribution with properly installed connection fittings – is the guarantee of an installation that will reliably serve for decades without leakage, corrosion or service costs that no one wants to even imagine after handing over the job.
Do you have a question on this topic?
Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.