Difference between Everline 25 and 32 pumps – which one is suitable for my system

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Difference between Everline 25 and 32 pumps – which one is suitable for my system

If you are choosing a circulation pump for your heating system and are deciding between the Everline 25 and Everline 32 series, you are not alone. This is one of the most common questions we encounter in practice. At first glance, the difference between these two series may seem unclear – after all, both series are wet-rotor circulation pumps for heating systems, both have a similar appearance and differ only by the number in the name. However, that number – 25 or 32 – indicates the nominal diameter of the pump connection, which directly affects which system the pump is suitable for and what flow it can ensure. This article will give you a complete overview of what distinguishes these two series, how to choose the right one, and what are typical application scenarios in practice.

If you have not yet read the article What do the numbers in the name of the Everline pump mean – diameter, head, spacing, we recommend starting there – it will help you better understand the entire nomenclature. In this text, we will focus specifically on the comparison of the 25 and 32 series and on practical decision-making between them.

What does the number 25 and 32 in the pump name mean

The first number in the name of the Everline circulation pump indicates the nominal diameter of the connection (connection flange) in millimeters. Everline 25 series pumps therefore have a connection with a nominal diameter of DN 25, which corresponds to the standard thread G 1¼" (inch thread). Everline 32 series pumps have a connection of DN 32, which corresponds to the thread G 1½".

This is not just a formal difference in the threads – a larger connection diameter means that the pump is designed for higher flow rates and greater hydraulic capacity. In other words: pumps of the 32 series are intended for larger, more powerful heating systems, where a pump of the 25 series would operate outside its optimal working range.

The second number in the name indicates the maximum pumping head in meters (maximum head H in meters of water column), and the third number is the axial distance between the connections (spacing) in millimeters. For example, Circulation pump Everline 25/6/180 has a connection DN 25, a maximum pumping head of 6 m, and a spacing of 180 mm.

Hydraulic parameters – where the series really differ

Aside from the connection diameter, there is an important difference between the 25 and 32 series in hydraulic capacity – that is, in the maximum flow (volume rate) the pump can provide. The connection diameter directly affects the pump's construction and the size of the flow path, and thus also its flow rate at the same pumping head.

Everline 25 series pumps typically cover flows up to about 4–5 m³/h (at low pumping head). Everline 32 series pumps are designed for higher flows – commonly up to 8–10 m³/h and more. This means that for larger heating systems with extensive distribution, the 32 series is a more appropriate choice, while for family homes and smaller apartment buildings, the 25 series is more than sufficient.

Specifically, from the Everline 25 series, for example, Everline 25/4/130 (maximum pumping head 4 m, spacing 130 mm) is suitable for compact systems with short spacing – for example, when installed in a gas boiler or a compact distributor. On the other hand, Everline 25/8/180 offers a pumping head of 8 m and a spacing of 180 mm, making it one of the most powerful models in the 25 series – still with a DN 25 connection.

Pump performance curve – how to read it

Every circulation pump has its characteristic Q-H curve (flow – pumping head). The X-axis represents the flow in m³/h (or l/h), and the Y-axis represents the pumping head in meters of water column. The higher and further to the right the curve is, the more powerful the pump. Pumps of the 32 series have the entire curve shifted significantly to the right – this means that at the same pumping head, they provide a significantly higher flow.

The practical conclusion from the curves is simple: if your system requires a high flow rate (a large number of heating units, long pipe runs), the 32 series will operate at a much more favorable point on its characteristic curve. Conversely, if you use a 32 pump in a small system, it will operate on the extreme left edge of the curve – that is, in an unfavorable hydraulic point, which leads to vibrations, increased noise, and reduced lifespan.

Connection spacing – a practical dimension for installation

The third number in the pump name is the spacing (center-to-center distance between connections) in millimeters. In practice, we most commonly encounter spacings of 130 mm and 180 mm, with 130 mm being less common in more compact boilers. This number is crucial when replacing a pump or installing it in an existing system – if the distance between connections is fixed in the piping, you must choose a pump with the same spacing; otherwise, the entire connection section must be redesigned.

In the Everline 25 series, both dimensions are available – for example, Everline 25/4/130 with a 130 mm spacing and Everline 25/4/180 with an 180 mm spacing. The 32 series mostly offers a 180 mm spacing, which corresponds to larger industrial and semi-industrial applications where greater space between connections is standard.

A typical pump replacement (e.g., for a damaged original pump) proceeds as follows: you determine the connection spacing on the existing pump, the thread diameter, and the maximum operating parameters (pressure, temperature, flow). Based on this, you select an appropriate model with identical geometric parameters.

For which heating system is the 25 series ideal

The Everline 25 series is designed with its construction and hydraulic parameters primarily for single-family homes, smaller apartment buildings, and compact heating systems. Specifically, these are typical scenarios:

Single-family home up to 200 m² of floor area – with standard radiator heating or underfloor heating in one floor, the 25 series is ideal. The boiler power here usually does not exceed 20–25 kW, which corresponds to a flow rate of up to 2.5–3 m³/h at a temperature drop of 10 K.
Replacement of an original DN 25 pump in an existing system – the most common scenario in service practice. The boiler or manifold has G 1¼" connections, so the 25 series is a direct replacement without any structural modifications.
Solar collector systems with smaller volumes – pumps of the 25 series are commonly used in solar circuits, where lower flows are sufficient and compactness plays a role.
Underfloor heating in a single-family home – an underfloor circuit usually does not require high flows at low temperature drops; the 25 series with higher head (e.g., model 25/6 or 25/8) can also cover a system with higher hydraulic resistance.
Secondary circuits in multi-circuit systems – when used with a manifold as a pump for one of the circuits, the 25 series is a cost-effective and available choice.

In practice, if you have a standard single-family boiler with a power of 15–24 kW, the Everline 25 series is your choice. Specific models such as Everline 25/6/180 or Everline 25/8/180 cover more demanding configurations in this segment, where higher head is required due to long pipe runs or a heating system with high resistance.

For which heating system is the 32 series more suitable

The Everline 32 series is used where the 25 series reaches the limits of its capabilities. Typical applications of the 32 series are:

Larger single-family homes and villas over 250–300 m² – with higher boiler powers (30 kW and more), the required flow increases, which the 25 series cannot efficiently ensure.
Apartment buildings and smaller commercial buildings – heating systems in apartment buildings with a boiler room, where one primary circuit supplies several secondary circuits with a total power of 30–60 kW.
Primary circuits in multi-circuit systems – in hydraulically separated systems with a pressure balancing device, the primary pump is dimensioned for the total flow; here, the 32 series ensures sufficient volumetric flow.
Systems with long pipe runs and simultaneously high flow – for example, industrial halls with finned heating units, where long pipe runs (pipe resistance) combine the need for higher head with increased flow.
Pool technologies and heat pumps – systems with air/water or brine/water heat pumps have higher flows in the primary circuit, where the 32 series operates much more efficiently.
Boiler rooms with a cascade of boilers – if you have two or more boilers connected in parallel (a cascade), the main circulation circuit requires an increased flow, for which the 32 series is dimensioned.

When to avoid the 32 series in a small system

This is an important practical note that customers sometimes overlook: bigger is not automatically better. If you install a 32 pump in a small single-family home with a 15 kW boiler, you will get a pump that will operate on the extreme left edge of its Q-H curve – at minimal flow and relatively high head. The result is:

vibrations and increased noise (characteristic hum from a misdimensioned pump)
increased electricity consumption (the pump does not operate at its optimal efficiency point)
reduced lifespan of mechanical and sealing components
possible problems with temperature regulation (excessive flow causes a small Δt and thus distorts regulation signals)

More about this topic is written in the article What circulation pump power do I need for my heating system, where you will also find specific calculation formulas for determining the required flow and head.

Comparison table – Everline 25 vs Everline 32

Parameter	Everline 25	Everline 32
Nominal connection diameter	DN 25 (G 1¼")	DN 32 (G 1½")
Typical max. flow	up to approx. 4–5 m³/h	up to approx. 8–10 m³/h
Available spacings	130 mm, 180 mm	mostly 180 mm
Typical applications	Single-family homes up to 250 m², apartment units, secondary circuits	larger single-family homes, apartment buildings, primary circuits
Boiler power	up to approx. 25 kW	25–60+ kW
Dependency on connection in the system	G 1¼" connection	G 1½" connection
Price	lower	higher

How to correctly determine which pump you need – step by step

In practice, I proceed with pump selection like this – and I recommend this approach to anyone who is unsure:

Step 1: Determine the heating source power

The boiler (or heat pump) power in kW is the basic input parameter. You can find it on the boiler's nameplate or in the documentation. For power up to 24–25 kW, the 25 range is the standard choice; for higher power, consider the 32 range.

Step 2: Calculate the required flow

The basic formula for the circulation pump flow is:

Q = P / (ρ × c × ΔT)

where P is the power in kW, ρ is the water density (≈ 1 kg/l at 70 °C it is about 0.978 kg/l, for simplicity we take 1), c is the specific heat capacity of water (4.186 kJ/kg·K) and ΔT is the temperature difference between the supply and return in K. For a typical radiator system with a supply of 75 °C and a return of 65 °C (ΔT = 10 K) and a power of 20 kW, the result is:

Q = 20 / (4.186 × 10) ≈ 0.478 kg/s = 1.72 m³/h

This flow is easily handled by the 25 range. At a power of 50 kW and the same ΔT, the flow would be 4.3 m³/h – here we reach the limit of the 25 range and it is appropriate to consider the 32 range.

Step 3: Determine the hydraulic resistance (pumping head)

The pump head H must overcome the resistance of the entire system – friction in the pipes, resistance of fittings, thermostatic valves and heating units. For a typical family house with a distribution of up to 50 m and standard radiators, the pumping head usually comes to 2–5 m. For more complex systems with floor heating and long circuits, it can be 6–8 m.

Step 4: Check the connections in the existing system

If you are replacing the original pump, inspect the existing connections. If you have G 1¼", simply choose the 25 range. If you have G 1½", the 32 range is your direct choice. If you are doing a new installation, adjust the pipe diameters and connections to the selected pump.

Typical practical scenarios from practice

Scenario 1 – pump replacement in a family house, boiler 18 kW

A customer from Trenčín had a damaged original pump in a gas boiler system. Boiler Baxi 18 kW, connections G 1¼", spacing 180 mm. System: radiator system, one floor, distribution approx. 40 m. Correct choice: Everline 25/4/180 or 25/6/180. The customer chose Everline 25/6/180 as a replacement with a reserve of pumping head for possible expansion in the future. The installation took 30 minutes, no modifications to the distribution.

Scenario 2 – new installation, two-story house, boiler 28 kW

A house with an area of 280 m², two-story, mixed system (radiators + part floor heating). Boiler 28 kW, the designer designed a spacing of 180 mm, connection G 1¼". Calculated flow at ΔT = 10 K: approx. 2.4 m³/h; estimated hydraulic resistance of the system: 5 m. Conclusion: Everline 25/6/180 is still fine – the flow of 2.4 m³/h lies comfortably within the working range of the 25 series. The client saved money compared to an unnecessarily oversized alternative.

Scenario 3 – boiler room of an apartment building, cascade of boilers 2× 30 kW

An apartment building with 12 apartments, a cascade of two gas boilers, total power 60 kW, the primary circuit supplies a hydraulic balancer, from which secondary circuits. Required flow in the primary circuit at ΔT = 10 K: 5.16 m³/h; hydraulic resistance of the primary circuit (short): 2 m. Here the range 25 is at its absolute limit and with any increase in resistance (clogged filters, partially closed valves) it could fall out of the working point. The Everline 32 range is the clear choice here – it works comfortably in the middle of its curve, with a reserve for both boilers and for possible expansion.

Scenario 4 – air/water heat pump, new build

New build 220 m², heat pump 12 kW (air/water), floor heating in all rooms. The floor system has a high hydraulic resistance (long circuits), the flow required at ΔT = 5 K (typical for floor heating): Q = 12/(4.186×5) ≈ 0.57 kg/s = 2.06 m³/h. The hydraulic resistance of the floor circuit was set by the project to 5.5 m. Everline 25/6/180 will cover this point with a slight reserve. The range 32 would be unnecessarily oversized and noisier.

Energy efficiency – EEI and energy efficiency classes

Modern circulation pumps are also assessed according to the Energy Efficiency Index (EEI). The lower the EEI, the more energy-saving the pump. Since 1 January 2013, the European ErP/Ecodesign directive has banned the sale of pumps with an EEI higher than 0.27; by 2015, the limit was reduced to 0.23. Everline pumps meet these requirements in both series.

When choosing between series 25 and 32, energy efficiency is another argument for correct sizing: a pump operating outside its optimal point on its Q-H curve consumes significantly more electrical energy than a pump operating at its point of maximum efficiency. With an average electricity price and annual operation (7,000–8,000 hours), a misdimensioned pump can consume up to 30–50% more electricity per year.

Read more about this topic in the article Everline vs. other circulation pump brands – quality and price comparison, where EEI values and real operating costs are also compared.

Installation and compatibility – what to check before ordering

Before ordering a new pump, I always recommend checking a few things directly on the existing equipment:

Outlet thread diameter – use a sliding caliper or a calibrated thread wrench. G 1¼" has an external thread diameter of approx. 41.9 mm, G 1½" approx. 47.8 mm.
Outlet spacing – measure from the central axis of the inlet to the central axis of the outlet. Common values are 130 mm and 180 mm.
Motor unit rotation direction – with horizontal piping, you can rotate the motor head by 90° or 180°, which is very important in tight spaces.
Maximum operating temperature and system pressure – most Everline pumps are designed for temperatures up to 110 °C and pressure up to 10 bar; check that your system does not exceed these parameters.
Type of medium – Everline pumps are primarily intended for water or water mixtures with non-freezing additives (ethylene glycol) up to a maximum of 30% by volume.

A detailed installation procedure can be found in the article Everline circulation pump installation – step-by-step guide, where typical installation errors and how to avoid them are also discussed.

Most frequently asked questions (FAQ)

Can I use the Everline 32 pump instead of 25 if I have G 1¼" connections in my system?

No, it is not straightforward. The pump 32 has G 1½" connections, so you cannot physically mount it on G 1¼" connections without reducing fittings. And even if you used these fittings, the pump 32 would operate outside its optimal point in a small system with low flow – with higher noise, vibrations and higher electricity consumption. The correct choice is to stay with series 25.

Higher head means a better pump – is that true?

No. A pump with a higher head has a greater reserve for systems with high hydraulic resistance on one hand, but on the other hand, it operates in an unfavourable point of the curve in systems with low resistance. Correct dimensioning means that the system operating point lies in the central part of the pump curve – not at the edges. Therefore, it is not worth unnecessarily buying a 25/8 model for a system where a 25/4 would be sufficient.

Everline 25/6/130 or Everline 25/6/180 – what is the difference?

The hydraulic parameters (maximum flow, maximum head) are the same for both models – the difference is exclusively in the connection spacing. The model Everline 25/6/130 has a spacing of 130 mm, the model Everline 25/6/180 has a spacing of 180 mm. Choose the one that matches the connection spacing in your system.

Everline 25 series – how long will it last?

With correct dimensioning, correct installation and regular maintenance, the standard lifespan of a wet-rotor circulation pump of this type is 10–15 years. Premature wear mainly occurs due to long-term operation outside the operating point (overdimensioning or underdimensioning), operation in dry mode or neglecting air venting. Learn more about maintenance in the article Maintenance and servicing of circulation pumps – what to check and how often.

Do I have to keep the same series (25 or 32) when replacing with Everline?

In principle, yes – maintaining the same connection diameter (and thus the same series) is the simplest way to replace without modifying the piping. However, if during the system inspection you find out that the original pump was significantly overdimensioned or underdimensioned (which is quite common in older installations), changing the series is justified. In that case, you also need to replace the appropriate fittings, reductions or modify a section of the pipe near the pump.

What are the signs that I have a misdimensioned pump?

The most common signs are: the pump makes a loud, bubbling or humming sound (cavitation or operation outside the operating point); some radiators are cold, while others overheat (uneven flow distribution); the boiler cycles too quickly or the system cannot reach the desired temperature. More detailed solutions to these problems can be found in the articles Noisy Everline circulation pump – causes and solutions and Common Everline circulation pump faults and how to eliminate them.

Conclusion – practical recommendation

Deciding between Everline series 25 and 32 is not about what is "better" – it is about what is correctly dimensioned for your specific system. In the vast majority of cases for family homes and smaller apartment units, the Everline 25 series is a fully sufficient and economically advantageous choice. Its models – from the compact Everline 25/4/130 to the more powerful Everline 25/8/180 – cover the vast majority of standard scenarios.

The Everline 32 series is used for larger buildings, primarily boiler circuits, cascade connections and systems with high-performance heat pumps, where the required flow is simply beyond the reach of the 25 series. If you are unsure, use the calculation procedure described in this article or read the more detailed guide in the article How to choose an Everline circulation pump for home heating – and always base your decision on the specific parameters of your system, not on speculation about what is "stronger".

Do you have a question about this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.