Frequently Asked Questions about DAB Pumps

Common questions about DAB pumps – answers from an expert

DAB pumps are among the most widespread circulation pumps on the Slovak market for heating systems, domestic hot water and cooling. Despite this – or perhaps precisely because of it – they are associated with dozens of recurring questions that customers, plumbers and service technicians encounter. Some are simple, others are quite technically interesting. In this article, we have gathered the truly most common ones that we encounter during sales, installation and service. We answer them directly, without unnecessary fluff – just like a technician would who has been through hundreds of installations.

What is DAB and why are these pumps so widespread?

DAB Pumps is an Italian company based in Mestrino near Padua, which has been manufacturing pumps since 1975. Today it is among the European leaders in the circulation pumps segment, as well as in pumps for drinking water, wastewater, garden systems and industrial applications. DAB pumps entered the Slovak market mainly in the heating segment and have since gained a strong position, primarily due to the combination of reliable Italian engineering with an acceptable price and good availability of spare parts.

Another reason is purely practical: DAB switched to energy-efficient electronically controlled pumps of class A very early on, as the European legislation (ErP directive) started to tighten. Customers naturally reached for DAB models because they met the standards and at the same time actually saved on electricity. This is still true today.

What is the difference between DAB EVOSTA2 and DAB EVOTRON?

This is by far the most common question. In short: EVOSTA2 is mainly intended for heating in family homes, while EVOTRON is a more versatile model with a wider performance range and greater control flexibility. Both are in energy class A and both use an electronically commutated motor (EC motor, i.e. without brushes, with permanent magnets).

In more detail: EVOSTA2 has an integrated differential pressure sensor and can automatically adapt to the needs of the system. It has three basic operating modes – constant pressure, proportional pressure and constant speed. In practice, most households with a radiator system set to proportional pressure and forget about the pump for years. EVOTRON also has an external input for control and is suitable for systems with multiple circuits or where integration with a boiler controller is required. A more detailed comparison can be found in the article DAB EVOTRON vs EVOSTA2 – which pump to choose in this Knowledge Center.

What size of DAB pump do I need?

Correct dimensioning is key and also the place where most people make mistakes. Either they choose a pump that is unnecessarily large (higher power consumption, noise, faster wear) or too small (insufficient circulation, cold radiators, boiler cycling too quickly).

The two basic parameters are: flow rate Q (in m³/h or l/min) and head H (in meters of water column, mWs). Flow rate depends on the boiler power and the temperature difference in the system. For a standard heating system with a 15–20 kW boiler and a temperature difference of 80/60 °C, the following is roughly valid:

• Flow rate Q = P / (c × Δt), where P is the boiler power in kW, c = 1.163, Δt = 20 K → at 15 kW you get Q ≈ 0.65 m³/h
• Head depends on the length of the piping and local resistances (valves, elbows, heat exchangers) – for a standard family home with 8–12 radiators and a circuit of up to 60 m, calculate H = 2–4 mWs

The model SADA with bracket DAB.EVOSTA2 40-70/180 has a maximum flow rate of 2.4 m³/h at zero head and a maximum head of 7 mWs. This is ideal for homes with a larger circuit or at a lower temperature difference (e.g. floor heating 45/35 °C), where the flow rate increases. Detailed sizing is discussed in the article What DAB pump power do I need for my home.

How much electricity does a DAB pump consume annually?

This is a question that often surprises our customers – in a good way. Old three-speed pumps (still millions of them installed in homes in Slovakia) consume 50–80 W in normal operation. Modern DAB EVOSTA2 or EVOTRON pumps operate at 3–15 W under normal load. That is not a typo.

Practical example: a customer from Bánovce nad Bebravou had an old circulation pump with a power of 65 W, running 24 hours a day during the season (October–April). That is 65 W × 24 hours × 210 days = 327.6 kWh. At a price of 0.18 €/kWh = about 59 € per year just for the pump. After replacing it with a DAB EVOSTA2 with an average consumption of 6 W during the same period: 6 × 24 × 210 = 30.2 kWh = 5.4 € per year. Savings of more than 50 € per year, with an investment payback period of 2–3 years.

The meaning of energy class A and what it really means is discussed in detail in a separate article Energy class A DAB pumps – what it means and why it is worth it.

What is a set with shut-off valves and why should you buy it?

Shut-off valves (ball valves with flanges) are components installed before and after the pump, allowing you to shut it down and replace it without having to drain the entire system. In older installations without shut-off valves, replacing the pump is a real hassle – you have to drain the heating system, which can take hours in some houses.

A DAB shut-off valve set includes compatible ball valves with the correct flange spacing, as well as gaskets if needed. It always makes sense to buy a set – both for new installations and for replacements. On atria.sk you can find, for example, a DAB.EVOSTA2 40-70/180 shut-off set, or the version a DAB.EVOSTA2 40-70/180 shut-off set with a FILTERBALL filter, where the shut-off valves are integrated with a magnetic-strainer filter. This is a solution that allows you to service the pump and the filter without draining the system.

What is FilterBall and why do some sets include it?

FilterBall is a patented filter system integrated directly into the pump’s shut-off valve. It includes a strainer and a magnetic trap for impurities (boiler sludge, oxidic deposits, ferromagnetic particles from old steel pipes). Magnetic trapping is important – standard strainers catch coarse mechanical impurities, but ferromagnetic sludge (black, muddy sludge common in old systems) passes through them and settles in the pump bearing.

Why is this important? In practice, we have seen several cases where a new pump stopped working properly within two seasons – not because it was faulty, but because sludge from the old system blocked the impeller. Installing a filter before the pump (or directly in the shut-off valve) dramatically reduces this risk. A more detailed view is provided in the article DAB pump with or without a filter – is the FilterBall set worth it?.

What is the correct installation procedure for a DAB pump?

Even for a simple pump replacement, it is worth following a few rules. First: the pump must be installed on the return pipe of the heating system – that is, where the water is cooler (typically 60–70 °C for condensing boilers and less). The reason is simple: the motor part of the pump is cooled by the operating liquid, and in too hot water (supply water), the motor degrades faster.

Second rule: the position of the rotor axis. DAB EVOSTA2 and EVOTRON pumps can be installed with a horizontal rotor axis (standard position) or vertically – with the electrical connector oriented upwards or sideways, not downwards. If the connector is oriented downward, condensation of moisture inside the electrical block and failure may occur. The appropriate positions are indicated on the pump label and in the manual.

Third rule: do not forget to bleed the system after replacement. Air in the system is the most common reason why the pump hums or does not pump well after installation. The bleed valve is located on the pump head (screw type). A detailed step-by-step procedure is available in the article Mounting a DAB circulation pump step by step.

The pump is humming or vibrating – what to do?

This is the second most common topic after “I don’t know how to choose the right model.” There may be several causes, and correct diagnosis will save you from unnecessary replacement of a working pump.

• Air in the system: Characteristic bubbling or irregular humming. Solution: bleed the pump and system, check the water pressure (should be 1–1.5 bar when cold).
• Deposits in the impeller: Constant noise, impeller is slowed down. Solution: the DAB service manual describes access to the impeller, or descaling (see the article Cleaning and maintenance of DAB pumps).
• Incorrect operating mode setting: A pump with constant speed in a system with thermostatic heads behaves noisier when the heads close. Solution: switch to proportional pressure mode.
• Too small shut-off valves or a clogged filter: Underpressure causes cavitation. Solution: check the filter, or replace it.
• Insufficient system pressure: Below 0.5 bar, the pump starts to have problems. Check the expansion tank.

More details, including error codes on the display of EVOSTA2 and EVOTRON, can be found in the article Common DAB circulation pump faults and their solutions.

What to do if the pump stops working during a power outage?

The circulation pump is the heart of the heating system and stops during a power outage. In a standard house, this is not an immediate disaster – the heating system with a boiler is not as dependent on the pump as, for example, a storage system. But a problem arises during a long outage in winter: without the circulation pump, the boiler overheats or simply stops, and the house starts to cool down.

DAB thought about this and for EVOSTA2 there is a solution in the form of a backup power source – an UPS module that keeps the pump running during a power outage for several hours. On atria.sk you can find a complete DAB.EVOSTA2 40-70/180 shut-off set with a backup power source. The battery is kept charged and activates automatically during a power outage – the customer may not even notice it. When and why you really need a backup power source is discussed in the article Backup power source for a DAB pump – when and why to use it.

Can I use the DAB pump for floor heating?

Yes, but you should keep in mind that floor heating has different operating parameters than radiators. It operates at lower temperatures (40–50 °C on the supply, 30–40 °C on the return), but with higher flow rates, because the circuits are longer. At the same time, floor heating has higher resistance – long PE-X or PERT pipes with a small diameter (16–20 mm) create significantly higher hydraulic resistance than steel radiator piping.

For floor heating with a manifold for 6–10 circuits in a house with an area of 120–150 m², we recommend a pump with a minimum head of 6 mWS and sufficient flow. In this case, the DAB EVOSTA2 40-70/180 is usually a suitable choice, or the EVOTRON for larger systems. It is important to check the pump's Q-H curve and compare it with the system's hydraulic resistance – the graph above in this article is for this purpose.

How long will the DAB pump last?

The service life of a DAB circulation pump, with proper installation and basic maintenance, is 15–25 years. This is not marketing – it is a reality confirmed by practice. Key factors that affect the lifespan are:

• Water quality: Hard water with high calcium content accelerates limescale formation in the rotor bearing. We recommend water treatment in areas with hardness above 20 °dH.
• System cleanliness: Sludge, corrosion, sand – all of these wear down the impeller and bearings. The FilterBall before the pump reduces this risk.
• Correct installation position: The connector should never be at the bottom, and the rotor should always be in a horizontal or properly oriented vertical position.
• System pressure: Underpressure (below 0.5 bar) causes cavitation and premature wear.
• Prevention: a quick annual check: check the pressure, bleed if necessary, and inspect the filter – 10 minutes a year that can extend the lifespan by years.

How to set up the DAB EVOSTA2 after installation?

EVOSTA2 has an intuitive display and one button. After the first power-on, it automatically starts in the default mode – proportional pressure, medium setting. For most standard heating systems with thermostatic valves, this is the ideal setting and no changes are needed.

The available modes are:

• PP (proportional pressure): The pump reduces the head with the flow – ideal for systems with thermostatic heads, where the flow changes according to room temperature. The most efficient and quietest mode.
• CP (constant pressure): Maintains a constant head regardless of the flow. Suitable for large systems without thermostats, e.g., older systems.
• CS (constant speed): Fixed speed – three levels. Suitable in exceptional cases, e.g., for special regulation requirements. Not energy efficient.

For a standard family home with a gas condensing boiler and radiators with thermostatic heads: set PP2 or PP3 (medium proportional pressure) and let the pump run. Under normal circumstances, you will never need to change this setting.

Is there a warranty on DAB pumps?

Yes. The standard warranty period for DAB pumps is 24 months from the date of purchase for private customers. Conditions for the warranty to be valid are:

• Proper installation in accordance with the installation manual (especially position, flow direction, power supply)
• Operation within technical parameters (pressure, temperature, medium)
• Purchase receipt

The warranty does not cover mechanical damage caused by foreign bodies in the system, corrosion from unsuitable medium, or damage caused by unprofessional installation. Therefore, it is worth installing a filter and entrusting the installation to a qualified person.

Is it worth buying DAB instead of other brands?

This is a question where we do not want to make purely marketing statements. The facts are: DAB is among the top 3 most sold circulation pump brands on the Slovak market. There are also other quality brands on the market – Grundfos, Wilo, Lowara. Grundfos and Wilo are generally more expensive, while Lowara is a subsidiary of Xylem and is in a similar price range as DAB.

For a private customer buying one pump for a family home, the decisive factors are: price, availability of service support and spare parts, and reliability proven in practice. In this respect, DAB performs very well – it is not the cheapest (those are Asian no-name products), but it has a much better service network and proven lifespan. When comparing specific models, look at the Q-H curves, energy class and power consumption – these will tell you more than any slogan.

Where can I find technical documentation for DAB pumps?

Each DAB model has an installation manual and technical specification sheet available on the official DAB Pumps website (dab-pumps.com) in the documents section. For models sold via atria.sk, the documents are also available directly on the product page. For example, for the DAB EVOTRON 40/130 or DAB VA35/130, you can find technical specifications directly with the product. We recommend downloading the relevant documentation before installation and archiving it together with the purchase receipt – this will save unnecessary searching in the case of a warranty claim or service.

How does the DAB VA35/130 differ from the EVOSTA2 and EVOTRON?

The model DAB VA35/130 is a representative of a different category – it is a three-speed pump with an asynchronous motor, not an EC motor with permanent magnets. Therefore, it is less energy efficient, but still reliable and simple. It is suitable for applications where the primary requirement is not energy class A, or where the customer is replacing an old circulation pump of the same type with a limited budget and wants a reliable replacement without complicated settings.

The difference in practice: VA35/130 is cheaper, consumes more (typically 35–50 W vs 3–15 W for EVOSTA2 in normal operation), but works well and without problems. For weekend houses, where heating runs only a few months a year, it is a fully acceptable solution. For year-round residential homes with a condensing boiler, we recommend investing in class A.

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Most frequently asked questions (FAQ)

Can I replace the old pump myself, without a plumber?

Technically yes – replacing a circulation pump is not classified as gas work and does not require special authorization. But you need to know what you are doing: close the valves, drain the water from the installation site, replace the seals, correctly orient the new pump, and bleed the system after filling. If you have shut-off valves, the replacement is relatively simple. If not, we recommend a plumber, as it will be necessary to drain the entire system.

The pump is showing a red indicator light – what does it mean?

The red indicator light on the EVOSTA2 indicates a fault condition. The most common reasons: rotor blockage (foreign object or limescale), flow operation issue (closed valve, air in the system), or an electronic error. First, check whether both valves before and after the pump are open. Then bleed the system. If the red indicator remains, read the error code in the manual or contact service. A more detailed description of error conditions can be found in the article Common DAB circulation pump faults and their solutions.

What is the correct water pressure in the heating system before the pump?

The minimum operating pressure for proper operation of the DAB pump (EVOSTA2, EVOTRON) is 0.05 MPa (0.5 bar) at the pump inlet. The optimal system pressure when cold (at room temperature, the system is filled, the boiler is off) is 1.0–1.5 bar. During operation, the pressure increases to approximately 1.5–2.0 bar. If the pressure gauge on the boiler shows less than 0.8 bar, add water via the filling valve and check the expansion tank.

Can I use the DAB pump for a solar circuit or cooling?

EVOSTA2 and EVOTRON are primarily dimensioned for heating systems with water or water with additives (antifreeze up to a maximum of 30% concentration). For solar collectors with special fluids (propylene glycol, synthetic oils), it is necessary to verify the compatibility of sealing materials – standard versions are not intended for full concentration of glycols. For cooling (floor cooling, fan-coil), the same applies – most standard EVOSTA2 versions can handle temperatures from 2 to 110 °C, which covers cooling, but you need to monitor condensation on the outside and insulate the piping.

Is the DAB EVOSTA2 40-70/180 suitable for a house with underfloor heating of 150 m²?

It depends on the specific project, but roughly: for underfloor heating of 150 m² with a heat loss of approximately 8–10 kW and a temperature drop of 45/35 °C, the flow is around 0.8–1.0 m³/h. The hydraulic resistance of underfloor loops depends on their length and diameter, but a standard distributor with 8 loops of 60 m from 16 mm pipe creates a resistance of 4–6 mWs. EVOSTA2 40-70/180 with a maximum head of 7 mWs covers this, but you are close to the maximum. For a comfortable reserve, we recommend EVOTRON 40/130, which has a significantly wider performance range.

What happens if I buy a DAB pump and after installation I find out it is unsuitable?

Standard commercial practice allows returning goods within 14 days after online purchase (Consumer Protection Act), but only if the product is unused and in original packaging. If the pump has been installed, returning it is more complicated. Therefore, we recommend: before purchase, verify the flow and system head, or ask – at atria.sk and in this Knowledge Center you have all the necessary tools for the correct selection. The article How to choose a DAB circulation pump for heating will also help you.

Conclusion

DAB pumps are a reliable, technically well-thought-out choice for most heating systems in single-family homes and apartment buildings. The key to long life and trouble-free operation is the correct selection of the model according to the hydraulic parameters of the system, professional installation with the correct position and shut-off valves, installation of a filter before the pump, and minimal annual maintenance. If you have doubts about the selection, use the other articles in this Knowledge Center – each of them deals with a specific sub-topic in depth, so you will find the answer without unnecessary searching on the Internet.

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