What do the numbers in the Everline pump name mean – diameter, pumping height, spacing

What do the numbers in the Everline pump name mean – a complete guide to the parameters

When you first open the category Everline pumps and look at the list of models, you will come across designations such as 25/4/130 or 25/6/180. For someone who has no experience with this type of equipment, this looks like a random combination of numbers. In reality, it is a concise but very informative code from which you can immediately read out three key pump parameters – and compare it correctly with other models without having to open the technical specifications.

In this article, we will examine each parameter in detail – what exactly each number represents, which physical quantity it describes, how it affects the practical use of the pump in the system, and above all – which pump is suitable for which type of installation. We will also add concrete examples from practice, because theory is a nice thing, but it is only with a real customer that it becomes clear what these numbers mean in real life.

Anatomy of the name: what is the first, second and third number

The designation of an Everline circulation pump always follows the same format: XX / Y / ZZZ, where:

• XX – the diameter of the connecting flange (in millimeters), i.e. the size of the threaded or flanged connection to the pipe
• Y – maximum pumping head, also called delivery head or manometric head (in meters of water column)
• ZZZ – pitch, i.e. the axial distance between the centers of the connecting flanges (in millimeters)

These three parameters will immediately tell you, when looking at any Everline model, what size pipe you will connect to it, what pressure it can handle, and whether it physically fits into the space you have available. Each of these parameters deserves its own chapter.

First number – diameter of the connecting flange (DN)

The first number in the Everline pump designation indicates the diameter of the connecting flange in millimeters. For the Everline models available on atria.sk, it is the value 25, which corresponds to the G 1½" thread (imperial thread standard). This is one of the most common sizes for circulation pumps in family homes and smaller apartment units.

In practice, this means that the pump is connected directly to steel or copper pipe with an external G 1½" thread, or via a transition from G 1½" to another size. Most boilers, valves and collectors in family homes are dimensioned exactly to this size, so customers do not need to worry about the compatibility of the connection when choosing an Everline model with the designation 25 – it fits the standard.

For interest: pumps with a larger diameter, for example with 32, are used in larger systems with higher flow – for example in underfloor heating of larger areas, in apartment buildings or in systems with multiple circuits. The topic of the difference between the sizes 25 and 32 is discussed in more detail in the article Difference between Everline 25 and 32 pumps – which one is suitable for your system, where you will also find comparative flow tables.

How is the flange diameter related to the pipe diameter in the system?

This is a question that often causes confusion. The DN or flange diameter designation of the pump does not refer directly to the outer diameter of the pipe in the system, but to the light of the thread (the inner diameter of the threaded connection). For typical heating systems in family homes, the following applies:

• Pipe DN 15 (½") – usually the main pipe in smaller apartment circuits
• Pipe DN 20 (¾") – very common in family homes
• Pipe DN 25 (1") – for larger capacities, systems with higher flow

An Everline pump with the designation 25 therefore has a G 1½" flange – this is a thread that is physically larger than the DN 25 pipe itself. This is because the pump must handle the flow from the entire system and at the same time have sufficient mechanical strength at the connection point. Between the system pipe and the pump flange, there are always valves, unions or transitions.

Second number – pumping head (manometric head)

The second number is the most important parameter from a technical point of view for the correct selection of a pump. It expresses the maximum transport head in meters of water column (shortened to m w.c. or m H₂O). This is the value that indicates how much resistance the pump can overcome – not only vertically (gravity), but also horizontally (friction in pipes, resistance of valves, heads, boiler and other components).

In the case of circulation pumps for closed heating systems (which is the case for radiator and floor heating in a family house), it is not about lifting water as with well pumps. It is about the total hydraulic resistance of the circuit that the pump must overcome to ensure the required medium flow (water).

What do the values of 4, 6 and 8 meters specifically represent?

In the Everline range available at atria.sk, you will find these pumping head values:

• 4 m – lower pressure, suitable for smaller systems with a simple layout and a few radiators
• 6 m – medium pressure, covers most typical heating systems in family homes
• 8 m – higher pressure, for larger houses, longer pipe runs, large floor heating areas or systems with higher local resistances

Specifically – Circulation pump Everline 25/4/130 with its 4 meters of pressure is suitable, for example, for a boiler with a simple two-pipe layout, 4–6 radiators and a total pipe length of up to about 60 meters. Everline 25/6/130 or Everline 25/6/180 can handle systems with a larger number of radiators or longer pipe runs – this is the most commonly ordered category for family homes with an area of 100–180 m². And Everline 25/8/180 is the choice for more demanding installations – for example, a combination of radiator and floor heating circuits, a larger house over 180 m², or older systems with deposits and higher pressure resistance.

How to calculate the required pumping head?

The basic formula we use in practice for dimensioning is based on the hydraulic resistance of the circuit. For a rough estimate in a typical family home, this simplification is sufficient:

Required pumping head (m) = length of the longest circuit (m) × 0.03 to 0.06

Where the coefficient 0.03 applies to new, well-dimensioned layouts with low valve resistance, and 0.06 for older systems with higher resistance or systems with thermostatic heads on all radiators. In addition to this, the boiler resistance (usually 1–2 m), the resistance of a collector or distributor (if present), and a reserve of 20–30 % are added.

Example: A house with the longest circuit of 50 meters, new piping, thermostatic heads on radiators, and a condensing boiler:

• Piping resistance: 50 × 0.05 = 2.5 m
• Boiler resistance: 1.5 m
• Valve and head resistance: 0.8 m
• Total: approx. 4.8 m → we choose a pump with a pumping head of 6 m (with a reserve)

A precise calculation of hydraulic resistances for a specific system is a topic for a separate professional analysis – you can find it in the article What circulation pump power do I need for my heating system, where we go through the calculation step by step.

Third number – flange spacing

The third number in the Everline pump designation indicates the spacing – that is, the axial distance between the centers of the left and right connecting flanges, measured in millimeters. In the available Everline models at atria.sk, we encounter two values: 130 mm and 180 mm.

This value is absolutely critical from an installation point of view. If you already have a pipe with a certain spacing prepared in the boiler room or technical room (which is usually the case when replacing an old pump with a new one), you must choose a pump with the same spacing. Otherwise, you will have to modify the piping – which is unnecessary work and unnecessary costs.

When to use 130 mm spacing and when 180 mm?

Historically, 130 mm spacing pumps have become very widespread in the Slovak and Czech markets, because such spacing was long dominant in models from established European manufacturers. Today the situation is more varied:

• 130 mm – standard spacing for most older installations, common when replacing an old pump in a house where the original pump had this spacing. This applies to models Everline 25/4/130 and Everline 25/6/130.
• 180 mm – longer variant, common in newer installations, in boilers where there is more space between the pipes, or in installations in a larger housing with valves and a filter. Models with 180 mm spacing are Everline 25/4/180, Everline 25/6/180 and Everline 25/8/180.

In practice, it looks like this: a customer calls and says their old pump has stopped working and they want to replace it. The first question I ask them is: "Measure the distance between the centers of both flanges for me." Without this number, I cannot recommend the correct model – the pumping head can be adjusted with a program, but the center distance cannot be changed physically without modifying the piping.

How to correctly measure the center distance when replacing a pump?

Measuring the center distance is not complicated, but you need to know exactly what to measure. Do not measure edge-to-edge or from the center of one flange to the edge of the other flange – it is always about the distance center-to-center, i.e., from the center of one opening to the center of the other opening. For a typical pump with a horizontal axis, this measurement is horizontal.

Practical procedure:

1. Turn off the system and wait for it to cool down
2. Close the valves on both sides of the pump
3. Measure the distance from the center of the left flange to the center of the right flange
4. Compare the result with the value of 130 or 180 mm
5. If the measurement comes out to, for example, 131 or 179 mm – it is still within the normal range, the measurement does not have to be precise to the millimeter

Combination of all three numbers – what it means in practice

Now that you understand each number individually, let's look at what the combination of all three numbers tells us about a specific model. Let's take two extreme models from the available range as an example:

Everline 25/4/130 – a small pump with lower pressure and shorter center distance. Typical application: an apartment with a boiler and a few radiators, or a replacement for an old type of pump in a boiler room where there is less space between the supply and return pipes. Advantage: compact dimensions, low energy consumption.

Everline 25/8/180 – a more powerful pump with the highest pressure and longer center distance. Suitable for a larger family house, a combination of underfloor and radiator heating, or a system with long pipe runs and multiple circuits via a manifold. It is also suitable for older installations with higher friction losses due to partial pipe clogging.

When choosing the right model, therefore, it is never based on just one number, but on the correct combination of all three. That is why we recommend verifying all three values before ordering – the center distance from the existing installation, the required pressure from the calculation or project, and the pipe diameter from the connected piping. The comprehensive logic of selection is discussed in the article How to choose an Everline circulation pump for home heating.

What the designation does not say – hidden parameters you should pay attention to

The three-digit code in the pump name is very practical, but it is not comprehensive. There are other technical parameters that you cannot read from it and must verify in the technical specifications:

Maximum flow (Q)

Head and flow are interrelated – higher flow reduces pressure and vice versa. A pump 25/6 will not deliver 6 meters of pressure at any flow – there is a characteristic Q-H curve, and the operating point must match the actual system conditions. Excessive pressure and low flow can lead to noise and cavitation.

Number of speeds / regulation

Everline pumps are equipped with multi-speed regulation – usually three fixed speeds or electronically regulated power with automatic adjustment. This is not indicated in the name, but it is important for energy savings. Modern electronically controlled pumps can reduce energy consumption by 50–80 % compared to old models with fixed speeds.

Temperature range and energy efficiency class

For standard heating systems, a temperature range of 2–110°C is common and covers most applications. Also important is the energy efficiency class (EEI – Energy Efficiency Index). Since 2013, stricter requirements have applied in the EU, and new circulation pumps must meet EEI ≤ 0.27. Everline pumps meet these requirements, which brings real electricity savings in long-term operation.

Direction of rotor mounting

Most modern pumps allow mounting in various positions – horizontal and vertical. However, the position of the terminal box (electrical connection) must remain in the upper half to prevent condensation from flooding in. This also does not follow from the designation and must be verified in the installation manual – or read the article Mounting an Everline circulation pump – step by step.

Practical scenarios for pump selection based on the designation

From years of experience, I know that customers most often make decisions in three situations: replacing an old pump, initial installation in a new building, or expanding the system. Each situation has its own specifics.

Scenario 1: Replacing an old pump in a family house

Mr. Novák has a house built in 1995 with steel pipes and cast iron radiators. The original pump has a G 1½" connection, a center distance of 130 mm, and the label on the plate says "Hmaximal = 4 m". After 25 years of operation, the pump has stopped working. The choice is simple: he needs a 25/4/130 pump or one with a slightly higher pressure of 25/6/130 (I recommend for older systems with higher friction losses). This avoids unnecessary drilling and pipe modifications.

Scenario 2: New construction with underfloor heating

Mrs. Kováčová is building a family house of 160 m² with underfloor heating in the entire ground floor and radiators on the upper floor. The manifold has 8 circuits, the longest circuit is 65 meters, and the system is new with low losses. The calculation says that at least 5.5 meters of pressure is needed. Choice: Everline 25/6/180 – sufficient pressure with a reserve, 180 mm center distance is standard in new installations with space. Alternatively, if there is more uncertainty, Everline 25/8/180.

Scenario 3: Apartment with limited space

An apartment in a panel building, small technical room, wall-mounted boiler. The piping is short – 4 radiators, the longest circuit 25 meters. The total hydraulic resistance does not exceed 3 m. A lift of 4 m would be sufficient here – and the spacing is important, which should be measured from the old pump. The most common value is 130 mm. Suitable model: Everline 25/4/130.

Everline model overview – quick glance

Model	Bore diameter	Head	Spacing	Typical use
Everline 25/4/130	G 1½"	4 m	130 mm	Apartment, small house, replacement for an old pump
Everline 25/4/180	G 1½"	4 m	180 mm	Apartment, small house, new installation with longer spacing
Everline 25/6/130	G 1½"	6 m	130 mm	Standard family house 100–160 m², older installation
Everline 25/6/180	G 1½"	6 m	180 mm	Standard family house, new installation, PV + radiators
Everline 25/8/180	G 1½"	8 m	180 mm	Larger house 180+ m², multiple circuits, long piping

Mistakes when selecting a pump based on the designation – what to avoid

Over the years of practice, I have seen several recurring mistakes that customers and plumbers make when selecting based on the designation:

Mistake No. 1: Selecting only based on the head without measuring the spacing

This is by far the most common problem. A customer knows they need a pump with a head of 6 m, orders an Everline 25/6/180, but during installation, it turns out that the previous pump had a spacing of 130 mm. The result: they have to modify the piping or return the product. Always measure the spacing before ordering.

Mistake No. 2: Choosing an overly powerful pump "just to be safe"

The logic of "better bigger, so it has a reserve" is counterproductive in the case of circulation pumps. An oversized pump operates at a suboptimal point on the curve, which leads to noise (typically humming or knocking), higher energy consumption, and faster wear. For more on the causes of noise, read the article Noisy Everline circulation pump – causes and solutions.

Mistake No. 3: Ignoring the bore diameter when installing with adapters

Installing a pump via reducing adapters is possible, but each adapter means additional hydraulic resistance and a potential leak point. If your system has a different size, it is better to consult a qualified plumber for the correct solution rather than improvising.

Mistake No. 4: Confusing the head in meters with power in kW

The head in meters is not the same as the pump power in kW or the heating system's thermal output. These values are related but not identical. The power of the pump in kW can be found in the technical specifications – and for modern electronically controlled Everline models, it is typically a value between 5–90 W depending on the speed setting.

Most frequently asked questions (FAQ)

Can I replace an old pump with a 130 mm spacing with a model with 180 mm spacing without modifying the piping?

No, it is not possible without modifications. If your system has piping prepared for a 130 mm spacing and you install a pump with 180 mm spacing, the ports simply do not match – they won't fit the valves or threaded connections. It is essential to either choose the correct spacing or have the piping extended by a plumber. Always measure the spacing of the original pump before ordering.

What happens if I choose a pump with a lower head than the system requires?

The pump will not be able to ensure sufficient media flow throughout all parts of the system. Distant radiators will be cold, the system will be unbalanced, and the boiler may cycle more than necessary. In extreme cases, overheating of nearby circuits and insufficient heating in distant rooms may occur. This is precisely why correct head dimensioning is crucial.

What if I measure the spacing and it comes out to, for example, 150 mm – what should I buy?

A spacing of 150 mm is not a standard value for Everline circulation pumps. It is possible that you measured edge-to-edge instead of center-to-center, or you have a different type of pump (e.g., a boiler-integrated pump). Double-check your measurement – measure the distance from the center of one port to the center of the other. If you really get a non-standard value, consult technical support or an experienced plumber.

All Everline models have the first number as 25 – are there other diameters available?

Yes, there are also pumps with the designation 32, meaning a G 2" bore. These are used in larger systems with higher flow – for example, in larger apartment buildings, industrial circuits, or systems with high boiler output. For standard family homes, the size 25 (G 1½") is standard and sufficient. A comparison of both types is covered in the article Difference between Everline 25 and 32 pumps – which is suitable for my system.

Is the head of 4, 6, or 8 m a fixed value, or does it depend on the speed setting?

The numerical designation in the pump name indicates the maximum head at the highest speed. At lower speed settings, the available head is lower – as well as the flow and energy consumption. A pump labeled 6 m may therefore achieve only 3–3.5 m head at the first speed setting. When selecting, always consider the maximum value to ensure the system works properly at the highest speed setting.

Do I need a professional for installation, or can I replace the pump myself?

Replacing a circulation pump is a relatively simple task that a skilled DIY enthusiast can handle – provided they know the correct procedure: closing the valves, releasing pressure, unscrewing and attaching the new pump including gaskets, refilling the system, and bleeding it. The entire process is described in the article Installation of Everline circulation pump – step-by-step guide. In Slovakia, however, if the boiler is gas-fired, the installation must be carried out or verified by a certified technician.

Conclusion – three numbers that determine the correct selection

The Everline circulation pump designation in the format XX/Y/ZZZ is a condensed technical description in three numbers. The first number – the bore diameter – indicates the physical connection and compatibility with the system. The second number – the head – determines the hydraulic performance and suitability for a specific type and size of heating system. The third number – the spacing – is a critical installation value without which you will not select the pump correctly.

If you check these three parameters before ordering – ideally by measuring on an existing pump and performing a simple hydraulic resistance calculation – you will choose the right model at first attempt. This will save you from unnecessary returns, delays in installation, and unprofessional improvisations during the installation.

For a deeper insight into the topic of selection, installation, and operation, we recommend further articles in our Knowledge Centre – from calculating pump performance, through comparisons with other brands, to solving common faults and noise issues. Each of them is based on real experience with dozens of similar projects and aims to provide information so that you can make decisions with more confidence – knowing what you are buying and why.

Do you have a question about this topic?

Are you unsure or dealing with a specific situation in your home? Write to us – we will be happy to help.

Name and surname Do not fill in this field:

Email

Message