Cleaning and maintenance of DAB pump – how to extend its lifespan

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Cleaning and maintenance of DAB pump – how to extend its lifespan

The circulation pump is the heart of every heating system. It circulates hundreds of liters of water daily, operates at temperatures up to 110 °C, and in modern homes runs practically non-stop 24 hours a day, seven days a week. Despite this, most households pay it no attention at all – until the characteristic gurgling, knocking, or the heating system simply stops working. From personal experience, I know that preventive maintenance can extend the lifespan of a pump from the usual 8–12 years to 15–20 years without major repairs. And since a quality electronically controlled pump today costs between 80 and 250 euros, it is an investment that is definitely worth protecting.

In this article, we will look at everything you need to know about proper care of DAB pumps – from basic rotor cleaning and air venting to chemical water treatment in the system, seal replacement, and diagnosing hidden faults. We will start with simple tasks that anyone can do with a 24 mm wrench, and move on to professional interventions for which I recommend calling a technician.

Why DAB pumps fail – real causes from practice

Before we get into specific procedures, it is important to understand what actually destroys pumps. From practice (and from hundreds of service calls I have reviewed with technicians), it is clear that the vast majority of premature failures have a common denominator: dirty water in the system. This is not a matter of owner negligence – it is simply physics and chemistry.

The heating system is a closed loop, but it is not hermetically isolated from the surrounding environment. Oxygen continuously enters the system through the expansion tank, bleed valve, or when water is added. Oxygen reacts with iron in the pipes and radiators, forming rust in the form of red-brown flakes. These settle in the lowest points of the system and in the pump rotor. In addition, with water hardness above 10 °N (German hardness degree, which corresponds to about 1.8 mmol/l), limescale forms, which clogs narrow passages and firmly adheres to balls or ceramic bearings in the rotor.

Another common cause is glycol or another antifreeze mixture, which oxidizes and turns into an aggressive acid if not regularly replaced. I have seen systems where the fluid was so degraded that its pH was below 6 – an acidic environment that corroded copper connections and bronze components of the pump.

Interestingly, electrical faults, which people immediately think of with every malfunction, make up only a small part of the problems. The vast majority of failures are mechanical and directly related to the condition of the water and the cleanliness of the system.

First step: how to recognize that the pump needs maintenance

The pump usually signals problems long before a real failure occurs. You just need to know what to look for and to listen. Here are specific signs that should lead you to a service inspection:

Noise, gurgling or knocking: If a pump that used to be quiet starts making a sound similar to boiling water or clicking, it is a classic sign of air bubbles (cavitation) or mechanical impurities in the rotor.
Uneven heating: Some radiators are warm, others are cold, even though you have bled them. The cause may be reduced flow due to a clogged rotor or a partially closed filter.
Increased electricity consumption: Electronically controlled pumps such as DAB EVOSTA2 or DAB.EVOTRON 40/130 have a power indicator on the display. If the pump constantly runs at a higher power than usual under the same outside temperature, something is adding resistance.
Leakage from the bleed screw: Moisture around the pump that was not there before may indicate a worn seal.
Error codes on the display: DAB EVOSTA2 and EVOTRON pumps display error codes such as E1 (blocked rotor), E2 (under-voltage protection), or E3 (temperature protection). A detailed overview of error codes can be found in the related article Common faults of circulation pumps DAB and their solutions in this Knowledge Center.

Deairing the pump – a basic task that protects the bearings

Air in the circulation pump is its number one enemy. An air pocket around the rotor causes the bearings and sliding sleeves to run dry – in the case of DAB pumps with ceramic bearings and graphite counterbearings, this can scratch the bearing surface within a few hours, resulting in permanent noise or increased vibration.

Deairing is therefore the first task that should be done regularly – I recommend at least once a year at the beginning of the heating season and then whenever any of the listed symptoms appear.

Step-by-step procedure for deairing a DAB pump

Turn off the pump (not the entire boiler room – just the pump) and let it stand for 5 minutes to allow the air to collect at the top.
Prepare an old cloth or a container – some water may spill during deairing.
On the front of the DAB pump (on the stator shaft, which is usually a round cover with a plastic central screw of size 6 or 8 mm), you will find the bleed screw (also called the "rotor plug").
Carefully loosen the screw – half to one turn is enough. Do not turn it more to avoid pulling it out.
Air will be heard escaping, then water will flow. At that moment, tighten the screw again – not too tightly (the thread is plastic or made of soft metal).
Start the pump and check whether the noise has disappeared.

Important notice: for pumps installed with a horizontal rotor axis (which is the most common case in Slovak boiler rooms), the air vent screw should be at the top. If the pump was installed upside down, the air venting will not be effective and air will remain trapped. More about the correct orientation during installation can be found in the article Installation of a DAB circulation pump step by step.

Cleaning the rotor – the most practical intervention in case of clogging

If air venting does not solve the problem and the pump is still noisy or does not produce sufficient pressure, it is time to look at the rotor. DAB pumps (as well as most modern circulation pumps) have a wet rotor – it is directly washed by the pumped liquid and lubricated by ceramic and graphite bearings. The advantage is a simple design without sealed shafts, the disadvantage is that any impurity in the water passes directly through the bearings.

What you will need

Ball valves before and after the pump (or shut-off valves from the set – see below)
A container for collecting water (at least 5 liters)
A cloth and an old towel
A flat screwdriver and a 17 or 24 mm wrench (depending on the model)
A soft brush or a toothbrush
Clean water for rinsing (or a 2–3 % citric acid solution in case of limescale)

Disassembly and rotor cleaning procedure for DAB

Before you start, make sure you have closable valves on both sides of the pump. If the pump was installed directly into the pipe without ball valves, you will have to drain the entire system – which is an unnecessary complication. Therefore, we recommend installation with shut-off valves, for example, from the set SET with shut-off valves DAB.EVOSTA2 40-70/180, where the ball valves are part of the package. Equally practical is the set SET with shut-off valves DAB.EVOSTA2 40-70/180 - FILTERBALL, which also includes an integrated ball filter before the pump, making the entire maintenance even simpler.

Close the ball valves on both sides of the pump.
Turn off the pump power supply – do not forget, it is an electrical device near water.
Place a container under the pump.
Unscrew the air vent screw and let the remaining water drain from the pump housing.
Unscrew the stator cap (the large plastic or metal cover on the front of the pump – usually 4 screws or a full circular cover). For DAB EVOSTA2 and EVOTRON models, the cap is opened using a larger flat screwdriver in the notches around the edge.
Pull out the rotor – it is a cylindrical part with a vane impeller at one end. In most DAB models, the rotor is pulled out directly, without a tool.
Inspect the rotor: look for red-brown sludge (corrosion), white deposits (limescale), or solid particles of sand and impurities.
Gently clean the rotor vanes with a soft brush under running water. Never use a metal wire or sandpaper – it will damage the balance of the rotor.
If limescale deposits are present, soak the rotor for 20–30 minutes in a 5 % citric acid solution (available at pharmacies or drugstores). The solution will dissolve the scale. Then rinse thoroughly with clean water.
Check the ceramic bearing – it is a small white disc in the center of the rotor. If it is cracked or significantly worn, replace the entire rotor (DAB spare parts are available).
Clean the rotor housing inside the pump with the same brush.
Reassemble the rotor, tighten the cap and the air vent screw, open the ball valves, and start the pump.

Filter cleaning – a critical step that is often skipped

Many installations include an angled filter or a ball filter (filterball) before the pump, whose purpose is to capture magnetic sludge and impurities before they reach the rotor. This filter must be cleaned regularly – at least once a year, and even twice a year in neglected systems.

The procedure for cleaning an angled filter is simple: close the shut-off valves, unscrew the lower valve of the filter (using 30 mm wrenches), remove the screen, rinse it under running water (or in a citric acid solution in case of heavy deposits), put it back in, and tighten. In the case of a ball filterball, the screen is built into the ball valve and cleaning is even faster – without full system shutdown.

If your system does not have a filter, consider adding one. The set DAB.EVOSTA2 40-70/180 - FILTERBALL includes it in the packaging and practically eliminates the need to clean the pump's rotor itself – the sludge will be caught at the filter, not in the pump.

Chemical system maintenance – protecting the pump from within

Mechanical cleaning is necessary, but not sufficient. Long-term protection of the pump depends on the quality of the water in the entire system. Here are specific steps of chemical maintenance that every owner of a heating system should complete at least once every few years:

1. Flushing the system

If the system contains visible sludge (black or rusty water when bleeding radiators), the first step is to flush it. Using the filling valve, we introduce a special flushing agent (e.g., Fernox F3 or Sentinel X400) into the system and let it circulate for 24–48 hours at normal operating temperature. After that, we drain the system, flush it with clean water, and refill it.

2. Corrosion inhibitor

After flushing, we add a corrosion inhibitor (e.g., Fernox F1, Sentinel X100 or Practikemi) to the cleaned system. The recommended dosage is usually 1 liter per 100 liters of water in the system. The inhibitor forms a protective film on the metal surfaces and significantly slows down the formation of rust and corrosion.

3. Water hardness check

If the water hardness in your area is above 15 °N (which is common in most of central and eastern Slovakia), I recommend softening the make-up water. A practical solution is single-use cartridges with ion exchange resin on the filling valve, which reduce hardness to below 3 °N. This significantly slows down the formation of limescale in the boiler and the pump.

4. Checking and replacing antifreeze mixture

In systems with glycol, I recommend testing the pH and concentration of the mixture every 3–4 years. The pH should be between 7 and 9. If it is lower, the mixture is degraded and corrosive – it needs to be completely replaced. A refractometer for measuring glycol concentration costs around 10–15 euros and is a one-time investment that can save expensive repairs.

Annual inspection – specific check list

The following check list is recommended to be reviewed every year at the end of summer or the beginning of autumn, before starting the heating season. Even though some items may seem obvious, in practice I see that these "obvious" things are often neglected for years.

☐ Visual inspection of the pump – moisture, corrosion on the surface, loose connections
☐ Bleeding the pump (procedure above)
☐ Bleeding all radiators in the house
☐ Checking and cleaning the filter in front of the pump if necessary
☐ Checking the setting of the speed stage or pressure curve (for EVOSTA2 and EVOTRON, it is a rotating switch or a button on the display)
☐ Checking the pressure in the system (manometer on the boiler – correct is 1.0–1.5 bar when cold)
☐ Checking the expansion tank (pre-pressure according to the project, usually 0.5–0.8 bar)
☐ Testing the function of the backup power source, if installed (more in the article Backup power source for DAB pump – when and why to use it)
☐ Recording the date of the inspection and the condition in the service record

Special situations – pump after a long period of inactivity

A common situation in summer cottages or houses with heat pumps for cooling: the pump is not used for 4–6 months during the summer. In such cases, the rotor can become "stuck" – sediment deposits mechanically block it. When you turn on the heating in the autumn, the pump will make a loud grinding noise and after a while it will stop – it will display error code E1 (blocked rotor).

The solution is simple if done in time: remove the bleed screw, insert a flathead screwdriver into the opening, and carefully turn the rotor back and forth. The sticky deposit will loosen and the rotor will start running. If that doesn't work, proceed with disassembling and cleaning the rotor according to the procedure above.

Preventive measure: in buildings with long summer shutdowns, I recommend manually starting the pump at least once a month for 5–10 minutes. Modern DAB EVOSTA2 pumps have an "anti-blocking" function – they automatically start briefly once every 24 hours, even if the thermostat does not require heating. Check whether this function is active in your model (in the menu under the key symbol).

When to call a professional and when you can handle it yourself

There is a clear line between what an average, resourceful homeowner can handle and what requires an electrician or heating technician:

You can handle it yourself (without professional skills): bleeding the pump, cleaning the filter, cleaning the rotor (without replacing parts), adding inhibitor, checking the pressure in the system.

We recommend a professional: replacing the pump's seal (risk of leakage), replacing the rotor or complete stator, diagnosing electrical faults (measuring insulation resistance of the winding), a jammed rotor that cannot be manually released, and any work on the electrical installation.

With models such as DAB VA35/130 with a more classic construction, the rotor is mechanically more robust and its replacement is simpler. With more sophisticated electronically controlled pumps, I recommend contacting an authorized service center in case of any doubts – the electronics are integrated directly into the stator and non-professional intervention can cause more damage than the fault itself.

How long a properly maintained DAB pump actually lasts

This is a question I receive very often. From practical experience, I can say that the difference between a neglected and a properly maintained system is dramatic. A comparison from real customer cases:

From my experience: a pump in a household with no maintenance at all (no bleeding, no filter, hard water without an inhibitor) starts to have problems on average after 8–10 years. A pump in the same type of house, where the owner bleeds the system every year, cleans the filter every two years, adds an inhibitor and monitors the pressure, functions without problems for 16–20 years. This is a difference in the value of 100–250 euros for the pump plus service call costs.

Special chapter: pumps with integrated backup power supply

If you have installed the DAB.EVOSTA2 40-70/180 with backup power supply set, in addition to the regular pump maintenance, you also need to take care of the backup power supply battery. The battery (usually lithium-ion or AGM) requires its own periodic inspection:

Once a year, check whether the backup power supply actually takes over the power supply during a power outage – disconnect the pump from the grid and observe whether it switches to the battery.
Check the battery voltage with a voltmeter (it should be at least 11.5 V for 12 V batteries under load).
AGM batteries have a service life of usually 3–5 years, lithium batteries up to 8–10 years – monitor the battery age and plan for replacement.
Keep the backup power supply permanently connected to charging – do not leave the battery discharged for long weeks.

Most frequently asked questions (FAQ)

How often should I clean the DAB pump?

We recommend air venting once a year at the beginning of the heating season. Cleaning the filter (if installed) at least once a year, twice in neglected systems. Disassembling and cleaning the impeller is not necessary every year – it is sufficient to do it when signs of clogging appear (noise, reduced flow, increased power consumption). In systems with good water conditions and regularly added inhibitor, you can avoid cleaning the impeller for years.

Can I clean the pump myself, or do I need a professional?

Depressurization, filter cleaning and impeller cleaning are tasks that can be handled by a typical, skilled homeowner without professional qualifications – provided that the pump has shutoff valves (ball valves) and the electrical supply is turned off. A professional is needed for replacing seals, diagnosing electrical faults, or if the impeller cannot be loosened by standard methods.

What should I do if the pump makes loud noise after cleaning?

Noise after cleaning and restarting is usually caused by air that was introduced into the system during disassembly. Depressurize the pump according to the procedure in this article and let it run for 5–10 minutes. If the noise persists, check whether the impeller is correctly mounted (it must be centered in the housing), and whether the ceramic bearing is cracked.

Is it worth buying a set with shut-off valves and a filter when replacing an old pump?

Definitely yes. Sets with shut-off valves and an integrated filter (for example, FILTERBALL sets) practically eliminate the need to drain the entire system for every service and prevent impeller clogging. The price of the set compared to a standalone pump is not significantly higher, but the long-term savings on service calls and the extended pump lifespan are significantly better. Learn more about choosing the right set in the article DAB pump with filter or without – is the filterball set worth it.

How many years will a DAB pump realistically last if properly maintained?

With annual inspection, regular air venting, maintaining water pH between 7–9 and using corrosion inhibitor, a lifespan of 15–20 years is realistic and common. The mechanical construction of DAB pumps (ceramic bearings, graphite-ceramic contact pair) is designed for such a lifespan. Premature failures are almost always the result of water contamination or neglected maintenance, not manufacturing defects.

What should I do with the pump if we are going away for a long time (cottage, summer house)?

If the system is full of water (without glycol) and freezing is not a risk, we recommend manually starting the pump at least once every 5–10 minutes to prevent the impeller from sticking. If freezing is a risk and the system is not drained, you must have a glycol mixture of the correct concentration – at least −15 °C, in extreme locations −25 °C. Glycol systems with a functional backup power supply are a much safer option for such properties, as explained in detail in the article Backup power supply for DAB pump – when and why to use it.

Conclusion: pump maintenance is not a luxury, but an economic necessity

The DAB circulation pump is a device that works continuously, often for years without anyone noticing it. This very discretion is a trap – people get used to it working and stop paying any attention to it. When a problem appears, it usually happens in February at midnight, when plumbers and heating technicians are on call and you have only 14 °C in your home.

Prevention costs much less than repair. One hour of your time once a year for air venting, filter inspection and system pressure check can extend the pump's lifespan by years. Adding a corrosion inhibitor for 15–20 euros every few years is much cheaper than replacing a pump for 150–250 euros plus service fee. And installing a set with shut-off valves and a filter – right when replacing the pump – is an investment that pays off during the first service.

If you are unsure about the model of your pump, its setting options or what specific error codes mean, we recommend visiting other articles in this Knowledge Center: DAB EVOTRON vs EVOSTA2 – which pump to choose, Energy class A DAB pumps – what it means and why it is worth it, and Common questions about DAB pumps. All products mentioned in this article are neatly listed in the category DAB pumps on atria.sk.

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