Frequently Asked Questions about Reduced T-Pieces from Hepworth

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Common questions about reduced T-pieces from Hepworth – a comprehensive overview for fitters and DIY enthusiasts

Reduced T-pieces belong to the category of fittings that are used far more frequently in practice than one might initially assume. Despite this, there are quite a few uncertainties surrounding them – from correctly reading the markings through selecting the right size to the technique of soldering. In this article, we have compiled the questions that repeatedly come to us: from plumbers who want to confirm their experience, as well as from DIY enthusiasts undertaking their first major intervention in a heating system. The answers are based on real-life customer experience with the Hepworth range of copper fittings.

What exactly is a reduced T-piece and how does it differ from a straight one?

This is a basic question that needs to be answered correctly before any purchase. A straight T-piece has all three outlets of the same diameter – for example, 22 × 22 × 22 mm. A reduced T-piece has one or more outlets of a different (usually smaller) diameter. This "asymmetrical" arrangement is precisely the reason why such fittings exist at all.

In practice, this means: you have a main pipe with a diameter of 22 mm and want to connect a radiator supplied by a 15 mm pipe. Instead of using a straight T-piece 22 × 22 × 22 and then a separately soldered reducer, you simply insert a T-piece 22 × 22 × 15 – and the problem is solved in one piece. Fewer joints, less work, fewer potential leak points.

The reduction on the branch is directly integrated into the body of the T-piece in the case of Hepworth fittings, not achieved by an additional welded insert. The wall of the fitting is cast from a single piece of copper, which ensures consistent material thickness and long-lasting joint durability.

How to correctly read the dimension marking – for example 28 × 22 × 28?

This is the second most common source of confusion. The marking of a T-piece is read in the following order: diameter of the first end of the straight flow × diameter of the branch × diameter of the second end of the straight flow. In other words: the first and third numbers describe the continuous (straight) axis of the fitting, while the middle number describes the branch (the perpendicular arm).

Practical examples:

22 × 22 × 15 – main pipe 22 mm, branch 15 mm. Typical use: a continuous 22 mm distribution with a branch to one radiator 15 mm.
28 × 28 × 22 – main pipe 28 mm, branch 22 mm. Typical use: a strong circuit (e.g. floor heating, larger radiator) from 28 mm with a connection to a smaller branch 22 mm.
22 × 15 × 22 – this situation is a bit different: the continuous axis is 22 mm, the branch is 15 mm, but both continuous outlets have the same diameter of 22 mm. At first glance, it looks the same as 22 × 22 × 15, but it is not the same. The difference lies in the direction of the reduction and which outlet is reduced – in the case of T-piece 22 × 15 × 22, the branch (the middle outlet) is reduced, while the continuous axis remains 22 mm.
28 × 22 × 28 – T-piece 28 × 22 × 28 has continuous outlets of 28 mm and a reduced branch of 22 mm. Practical application: a strong boiler circuit 28 mm with a branch to a less powerful radiator or secondary circuit 22 mm.
28 × 15 × 28 – T-piece 28 × 15 × 28 is interesting in that it solves a large diameter jump (28 to 15 mm) with a single fitting. This is useful, for example, when you are supplying one small radiator from a very strong circuit without an intermediate link.

A more detailed explanation of the marking system can also be found in the separate article Dimensions of reduced T-pieces: how to read the marking 22 × 22 × 15 in the Knowledge Centre.

Why does Hepworth have such a good reputation and is it just marketing?

Hepworth is a British manufacturer of copper fittings with a history stretching back decades. Their products have become an established professional choice on the Slovak market, especially among plumbers who prefer predictable quality over cheap alternatives of unknown origin. What exactly is behind this reputation?

Copper purity: Hepworth fittings are made from high-purity copper (Cu-DHP, deoxidized copper), which is a prerequisite for good soldering – the sockets are homogeneous, without inclusions, and the surface is consistent.
Dimensional tolerances: The inner diameter of the sockets is sized to fit standard copper pipes in accordance with EN 1057. This means that the pipe easily fits into the socket, but without clearance – which is the basis for a good capillary joint.
Wall thickness: Unlike cheaper fittings, where the wall thickness dramatically decreases at the reduced socket, Hepworth maintains an appropriate thickness even in the transitional zone.
Repeatability: When a fitter gets used to one product and knows how to solder it, they appreciate that each new pack provides the same result. No surprises in tolerances.

This has a real impact in practice: with Hepworth fittings, it rarely happens that a joint "just won't take" or that the pipe doesn't fit properly. Of course, even the best fitting won't save poor soldering technique – but a good fitter with good material works more reliably and faster.

Which reduced T-piece should be chosen for a specific situation?

This is probably question number one. The answer depends on three factors: the diameter of the existing pipe, the diameter of the branch being fed, and the direction of flow (i.e., which socket is the run and which is the branch).

Scenario 1: Radiator supply from a 22 mm run

A classic situation in apartment buildings and houses with central heating. The run is in a 22 mm pipe, and the radiator is supplied by a DN 15 (= ½") valve with a 15 mm supply. The correct choice here is the T-piece 22 × 22 × 15. The 22 mm run remains uninterrupted, and the 15 mm socket branches off to the radiator.

Scenario 2: A strong heat source circuit, secondary connection

The boiler supplies a strong 28 mm circuit (e.g., at a power above 20 kW or a long run). From this circuit, you want to branch off to a secondary branch or a group of radiators supplied by 22 mm piping. There are two options here: T-piece 28 × 28 × 22 (28 mm run, 22 mm branch) or T-piece 28 × 22 × 28 – essentially the same result, but sometimes the physical orientation of the sockets in space differs, so it's good to know which socket is on the right and which is on the left.

Scenario 3: A large diameter jump – from 28 mm directly to 15 mm

Less common, but real – for example, when you are doing a renovation and an existing strong 28 mm circuit has only one small radiator added later, supplied by 15 mm. Instead of two fittings (T-piece + reducer), a T-piece 28 × 15 × 28 is sufficient. However, be careful with hydraulics: a large diameter jump can cause insufficient flow through the small branch if the balancing valves are not properly set. Hydraulic balancing is necessary.

Scenario 4: The branch is the main route, the run is the secondary

Sometimes it's the other way around – water comes into the T-piece from one direction, and most of the flow branches off, while only a small part flows straight. In such a case, it's important to consider which socket is the "run" and which is the "branch," because the hydraulic resistance of the T-piece is not symmetrical. More on this decision-making can be found in the article When to use a reduced T-piece instead of a straight one in heating distribution.

Can a reduced T-piece be installed in any orientation?

Yes, Hepworth copper T-pieces have no strict requirements regarding the direction of fluid flow – they are not valves or strainers. You can install the T-piece with the branch facing up, down, or to the side. What matters is that the joint is properly soldered and the pipes are sufficiently supported to prevent the joint from being stressed in tension.

Practical caveat: if the branch is directed directly downward and water can stand there (e.g., during system venting), we recommend installing an air vent or ensuring that the system has the correct pipe slope in each outgoing branch. This is not a question of fitting quality, but of proper system design.

Is soldering a reduced T-piece different from soldering a straight one?

Technically, no – the procedure is the same. It involves either hard or soft soldering using a capillary joint. The difference is that with reduced fittings, you must ensure that each diameter is properly heated, as different pipe diameters heat up at different speeds. A thinner 15 mm pipe reaches soldering temperature faster than a thicker 22 mm or 28 mm pipe.

Basic soldering procedure:

Cut the pipe at a right angle and remove burrs from the inside and outside.
Use sandpaper or a brush to clean the end of the pipe and the inside of the fitting socket to a metallic shine.
Apply flux thinly and evenly to both surfaces.
Insert the pipe into the socket until it reaches the bottom.
Heat the joint evenly with a flame, moving the flame around. With a reduced T-piece, heat the larger diameter first, then the smaller one – but in practice, you do this almost simultaneously by moving the flame.
Apply the solder (copper-tin for potable water, or a specialized type) when the correct temperature is reached – the solder should flow into the capillary by itself, not be melted directly by the flame.
Let it cool naturally, do not cool it with water.
After cooling, remove any remaining flux with a damp cloth.

A detailed step-by-step procedure can be found in the article Installation of a reduced Hepworth T-piece: soldering step by step.

What are typical mistakes when selecting and installing reduced T-pieces?

Over the years of practice, the same mistakes tend to repeat. Here are the most common ones:

1. Confusing the order of numbers in the designation

The customer orders 22 × 22 × 15 instead of 22 × 15 × 22. The difference looks minimal on paper, but during installation, it can mean that the branch is in the wrong place or has the wrong size. Always check which socket is the run and which is the branch, and compare it with what you need in the specific part of the system.

2. Insufficient cleaning before soldering

The most common cause of leaky connections. Copper oxidizes quickly, especially on a construction site where a pipe lies for several days. Flux alone is not enough to cover strong oxidation – mechanical cleaning is necessary before each soldering.

3. Too large a diameter jump without hydraulic balancing

Using a 28 × 15 × 28 T-piece without subsequent hydraulic balancing can result in minimal water flow through the 15 mm branch, leaving the radiator cold. The fitting itself will not solve the problem – the flow must be properly adjusted using a balancing valve or a thermostatic valve with pre-setting.

4. Installation of a T-piece in a confined space without access for soldering

Soldering in close proximity to flammable materials (e.g., wooden board, plastic pipe) or in a space where the flame cannot be properly directed is risky. Either ensure protection (mineral wool, fire-resistant foil) or consider alternative connection techniques (press-fit, crimping), if the system allows it.

5. Neglecting pipe support

A reduced T-piece is a place of diameter change – that is, a place of pipe stiffness change. If the pipe is not supported at a sufficient number of points, vibrations and thermal expansion will mechanically stress the joint. This shortens the lifespan of even a perfectly made joint.

Read more on this topic in the article Common mistakes when installing copper T-pieces and how to avoid them.

What pressure and temperature parameters can these fittings withstand?

Hepworth copper fittings are dimensioned for standard central heating applications. Standard parameters for a soft-soldered capillary joint (solder based on Sn-Cu or Sn-Ag-Cu):

Maximum operating pressure: 16 bar (at temperatures up to 65 °C)
Maximum operating temperature: 110 °C (at pressure up to 10 bar, with appropriate solder)
For potable water: use lead-free solder and flux approved for potable water.

For standard central heating with a low-temperature boiler (55–70 °C) and pressure 1.5–2.5 bar, you are well below the limits. For condensing boilers operating at higher temperatures (e.g., output 80 °C), it is still acceptable. Problems arise only in extreme applications (steam systems, high-temperature industrial lines) – in these cases, reduced Hepworth T-pieces for heating are unsuitable.

Can Hepworth fittings be combined with other brands?

Yes. Hepworth fittings are manufactured according to the EN 1254-1 standard, just like most quality European manufacturers. Diameters and tolerances are standardized, so a copper pipe in accordance with EN 1057 with a 22 mm diameter will fit into a 22 mm Hepworth fitting regardless of the pipe manufacturer. It is also possible to combine a Hepworth T-piece with another brand’s elbow or coupling – provided it is a soldered capillary fitting according to the same standard.

A warning applies to press-fit (crimped) systems: in these cases, fittings and pipes are tied to a specific production line and combining them is problematic. This does not apply to classic soldered Hepworth fittings.

How many fittings do you need for a typical family home?

Estimate for an average family home with 8–10 radiators, one boiler, and a standard two-pipe system:

For each radiator: 2 reduced T-pieces (supply + return)
Total: 16–20 reduced T-pieces
Common combination: 22 × 22 × 15 for floor-level distribution, 28 × 28 × 22 or 28 × 22 × 28 for boiler branch

In addition, you will need straight T-pieces (where the same diameter branches), elbows, couplings, and reducing pieces. The total number of fittings during a central heating renovation in a family home easily reaches 60–80 pieces including all types.

A good practice is to make a simple layout diagram with marked branch points and write down the triplet of numbers at each T-joint. This way you can easily count how many pieces of each type you need. You will save a trip to the store for a forgotten fitting – this is a loss every experienced plumber knows well.

What are the differences between soft and hard soldering for these fittings?

For standard central heating, soft soldering is used (temperature 180–250 °C, tin-based solder). It is more accessible, faster, and does not require special equipment other than a quality torch. Most plumbers use a gas torch with butane or propane-butane.

Hard soldering (silver brazing, temperatures 600–900 °C, brass or silver filler material) is used for high-pressure and high-temperature applications, or where higher mechanical strength of the joint is required (e.g., industrial lines, cooling). For standard heating in family homes, hard soldering is overdimensioned and unnecessarily demanding in terms of material and technique.

Important warning: with hard soldering, overheating of the fitting can change the copper structure at the capillary location, which paradoxically can weaken the joint if done by an inexperienced hand. For Hepworth fittings used in heating, we therefore recommend standard soft soldering – unless the project conditions require otherwise.

Can a reduced T-piece be disassembled and reused?

Technically yes – a soldered joint can be heated with a flame to disconnect it, the fitting can be removed and reused. In practice, however, this is done only rarely and with caution. During disassembly, minor defects, oxidation, or solder residue in the socket may appear on the fitting and pipe, complicating re-soldering. If you remove the fitting, we recommend:

Thoroughly mechanically clean the inside of the sockets with a brush or abrasive.
Visually inspect to ensure there is no visible deformation or crack on the fitting.
Apply fresh flux and solder using the same procedure as for a new fitting.
After soldering, pressure test it before covering the line.

From an economic point of view – the price of one fitting is lower than the labor and risk associated with recycling. If you have doubts about the condition of a disassembled fitting, it is more reasonable to replace it with a new one.

Most frequently asked questions (FAQ)

What is the difference between a T-piece 22 × 22 × 15 and 22 × 15 × 22? Are they the same?

They are not. In the designation of a T-piece, there are always three numbers: the first and third describe the running branch (left and right socket), the middle number describes the branch. The T-piece 22 × 22 × 15 has running sockets of 22 mm and a branch of 15 mm. The T-piece 22 × 15 × 22 also has running sockets of 22 mm, but the middle socket – branch is 15 mm. In this particular case, the result is the same, because the running sockets have the same diameter and only the orientation of the marking differs. However, in the case of asymmetric fittings (e.g. 28 × 22 × 15), the order of the numbers would mean a significant difference in the physical arrangement of the sockets. Always verify which socket is where before installing the fitting.

Why is my joint not sealing, even though I followed the procedure precisely?

The most common causes are: insufficient mechanical cleaning of the surfaces before soldering (oxidation prevents wetting), insufficient heating of the joint (the solder did not flow into the entire capillary), presence of moisture or oil on the surface, or movement of the joint during the solder solidification. Less often – but also – it may be due to incorrect solder or expired/low-quality flux. Try the joint again – heat it up, disassemble, clean, apply fresh flux and solder from the beginning.

Is it possible to use Hepworth fittings on existing old copper pipe during reconstruction?

In most cases yes, provided the old pipe meets EN 1057 (standard outer diameters 15, 22, 28 mm). Problems may arise if the old pipe is heavily corroded from the outside or has a non-standard diameter (e.g. old imperial dimensions in inches). In such a case, the pipe diameter may differ by tenths of a millimeter from the standard, which may make it difficult to insert into the socket or, on the contrary, cause excessive clearance. We recommend always testing "dry" before applying flux.

Can I use a reduced T-piece Hepworth in a floor heating system?

Copper T-pieces Hepworth are installed in distributors and main lines leading to floor heating distributors (floor heating systems are usually plastic – PEX or multilayer, not copper). Copper distribution lines are therefore in the part from the boiler to the distributor. Hepworth T-pieces are fully suitable for this part. The floor heating circuits themselves are usually plastic, so copper fittings are not used there.

How many T-pieces 28 × 28 × 22 do I need for a two-pipe system with five radiators on one floor?

For five radiators in a two-pipe system, you need two T-pieces per radiator – one on the supply pipe, one on the return pipe. In total, you need 10 T-pieces. The type of fitting depends on the diameter of the main line and the diameter of the radiator supply. If the main line is 28 mm and the radiator supply is 22 mm, you will use 10 pieces of T-piece 28 × 28 × 22. The last radiator in the row usually does not require a T-piece – the pipe is terminated directly with elbows and straight pieces.

Where can I find information on correct hydraulic sizing for different diameters?

For basic orientation, we recommend the article How to correctly choose a branch reduction when feeding a radiator from the main pipe and the article Combining different diameters in a heating circuit using reduced fittings. Both can be found in the Knowledge Center at atria.sk. For precise hydraulic calculations (pressure losses, flow ratios), we recommend consulting an HVAC designer or using specialized software.

Conclusion: Reduced T-piece – a small fitting, a big impact on the whole system

Reduced T-pieces Hepworth may seem like inconspicuous pieces of copper at first glance, but their correct selection and installation have a decisive impact on the hydraulic balance, tightness and long-term reliability of the entire heating system. You may buy a top-class boiler and modern radiators, but if the distribution is hydraulically unbalanced due to poor choice of fittings – the whole system will operate suboptimally.

Investing in the right fittings (and their correct installation) pays off for many years of trouble-free operation, lower energy costs and peace of mind that there are no leaking joints behind the drywall or in the floor. Hepworth reduced T-pieces are a proven choice for those who do things right from the start.

The full range of reduced T-pieces can be found in the category of reduced T-pieces at atria.sk.

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.