How to clean the heat exchanger in a gas boiler

For many homeowners, keeping their house warm and comfortable throughout the winter is of utmost importance. The heat exchanger in your gas boiler is a vital part of your heating system that is frequently disregarded. This essential component is in charge of sending heat from the combustion process to the heating system in your house. But as dirt, debris, and other buildup accumulate over time, the heat exchanger may become less efficient and may even become dangerous due to expensive repairs.

Maintaining the efficiency of your gas boiler and safeguarding your family’s safety depends on knowing how to clean the heat exchanger correctly. Frequent maintenance increases your heating system’s lifespan and efficiency, which will ultimately save you money and give you peace of mind.

Get familiar with the fundamentals of how a gas boiler operates before beginning the cleaning procedure. To put it simply, a gas boiler heats water, which warms your house as it travels through pipes to radiators or underfloor heating systems. Heat is produced during combustion and is transferred to the water through a heat exchanger. Any accumulation on the heat exchanger may prevent this transfer, resulting in lower performance and possible malfunctions.

Thankfully, there’s no reason why cleaning the heat exchanger in your gas boiler has to be a difficult undertaking. By utilizing appropriate equipment, supplies, and expertise, it is possible to eliminate any accumulation and reinstate the effectiveness of your boiler. It’s crucial to remember that while some homeowners might feel confident handling this task on their own, others might would rather call in a professional. Regardless of how you choose to clean the heat exchanger, knowing what needs to be done is crucial to keeping your house warm and cozy.

We’ll address a typical home maintenance task in this article: cleaning your gas boiler’s heat exchanger. The heat exchanger may accumulate dirt, dust, and debris over time, which could lower its efficiency and lead to issues. Frequent maintenance can help your boiler last longer and function more efficiently. We’ll take you through each step of cleaning the heat exchanger, from turning off the boiler to getting safe access to it to using the right cleaning supplies and methods. You can make sure that your gas boiler runs effectively, keeping your house toasty and comfortable while saving you money on energy costs, by following these easy steps.

How to clean and what to flush the heat exchanger of a two-circuit gas boiler

Periodic maintenance is necessary for heating boilers and almost any other technological equipment that operates in challenging conditions. The cleaning of the gas boiler’s heat exchanger is one of the most crucial procedures performed during maintenance.

Why it is necessary

Heat-exchangerThe heat exchanger is a metal (or cast iron) box with an integrated radiator that transfers heat to the fluid flowing inside by being heated from the outside by a burner flame. The heat exchanger operates at peak efficiency when it is clean, providing nearly all of the energy received for heating. But over time, different impurities—compounds dissolved in the coolant salts—start to precipitate on the walls of the internal channels (scale). If hard water is used in the DHW mains, there is particularly intense lime deposit formation in the secondary heat exchanger of a two-circuit boiler.

Such contamination of heat exchanger channels can result in a number of unpleasant outcomes, including:

  • Reduction of boiler efficiency. Mineral deposits have much lower thermal conductivity than metal, so much more energy will have to be spent on heating water. Accordingly, gas consumption will also increase.
  • Overheating of the heat exchanger. The scheme of operation of gas boilers assumes that the coolant coming from the return mains cools the internal cavities of the heating element. When scale appears, cooling efficiency drops, the heat exchanger overheats and quickly breaks down.
  • Breakdown of heating equipment. Mineral deposits on the internal walls of the heat exchangers make it difficult for the coolant to flow through them. This creates an additional load on the circulation pump, which will quickly exhaust its resource if the narrowed channels are not cleaned in time.

As a result, regular flushing of the heat exchanger will help to reduce fuel consumption to the absolute minimum and save a significant amount of money by preventing the failure of costly components.

Frequency of heat exchanger cleaning

There is a lot of conflicting information available in different sources regarding how frequently different heating boiler components should be cleaned. The maintenance intervals are typically listed in the instructions specific to a given model. It is important to remember that these data are approximations and are intended to be used in optimal operating environments. Heat exchangers may actually require more frequent flushing.

A number of indirect indicators that accompany the operation of the gas boiler can be used to determine the severity of the heat exchanger’s blockage:

  • A noticeable increase in gas consumption. Practice shows that the increase in fuel consumption due to deposits inside the heating element can reach 15%;

This is the heat exchanger’s appearance following prolonged use.

Modern boilers are built to last a long time, and replacement parts can get expensive. As a result, as soon as the aforementioned symptoms appear, the heat exchanger needs to be thoroughly cleaned. If not, heating boiler maintenance expenses may rise significantly.

Methods of cleaning heat exchangers

Different methods can be used to flush the heat exchanger. We will discuss them in more detail later on, and in the meantime, we’ll cover how to clean a two-circuit boiler’s heat exchanger, which is especially prone to the buildup of organic deposits.

Manual cleaning

To use this method, the boiler’s heat exchanger needs to be fully removed for unrestricted access. After that, it can be cleaned using a variety of tools:

  • Mechanical cleaning. Remove deposits from the inner surface can be removed with a hard metal brush or a special scraper;
  • Flushingin special compositions. Most often the parts of heat exchangers are soaked in a solution for acid washing. This method is particularly effective for removing heavy fouling, for example in the ducts of two-circuit gas boilers.

The manual cleaning approach is easy to use and efficient. It is feasible to use it on its own to independently flush the heat exchanger. The only caution is to make sure all connections are airtight and to exercise caution when working with boiler sealing elements.

Hydrodynamic cleaning

Heat exchangers in gas boilers can be flushed without having to disassemble the boiler.

The process of mechanically removing scale from pipeline walls using high-pressure water jets—which occasionally include small abrasive particle impurities—is known as hydrodynamic cleaning.

Special installations that can inject pressure up to 1.5 thousand bar into the mains are used to carry out this procedure. This method of cleaning heat exchangers is the most efficient, albeit costly.

Chemical cleaning

Chemical cleaning of gas boiler components involves introducing an acidic solution into the system with the aid of a specialized apparatus known as a booster. The heat exchanger is then cleaned by running this solution through it for a number of hours. The most challenging deposit types to remove with this method are trivalent iron and carbonate scale.

Before and after cleaning of the heat exchanger

The high expense of the reagent, metal deterioration, and a significant volume of hazardous waste are the drawbacks of chemical cleaning.

Heat exchanger flushing fluids

Let’s finally address the issue of what to use to clean the gas boiler’s heat exchanger. Even though there are a lot of suggestions in different places, care should be taken when selecting a cleaning solution.

Hydrochloric acid is highly recommended by many experts for flushing. While it works well as a descaling agent, the compound’s aggressive nature poses a risk of damaging the heat exchanger’s internal protective coating.

Furthermore, there is proof that brittle metal can result from hydrochloric acid flushing.

Citric acid poses less of a risk to the heat exchanger’s material. It works flawlessly with every type of deposit and unique reagents, such as DETEX, Cillit, Sanax, and others.

The lifespan of a heating system can be extended and maintenance expenses can be decreased with timely and appropriate maintenance. The heat exchanger will have the biggest impact on this procedure because it is one of the most crucial tasks completed during boiler maintenance.

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Methods for cleaning heating batteries

Natalia, depending on the boiler design, the following operations should be done:
1. Using a long screwdriver, remove the front cover of the unit, the protective cover and the combustion chamber deflectors.
2. Disconnect any interfering wires from the flow sensors, temperature sensors, etc. д. as well as pressure pipelines (in order not to forget how they are connected, you can photograph the internal filling of the unit).
3. Remove the fan and exhaust gas deflector.
4. The plate heat exchanger itself is similar to the radiator of a car heater and is fixed on snaps.
5. When removing the device, avoid sharp movements and mechanical impact – it is very easy to damage the heat exchanger.
6. When disconnecting the copper tubes from the radiator, be sure to hold the nuts at the base of the unit with a second wrench, otherwise you may damage the outlet connections of the unit.
After cleaning the heat exchanger, it is installed in reverse order.

December 11, 2015

Here are some situations where cleaning is required: 1. The device’s computed values are much different from the passport’s values; the heat exchanger uses more heat energy while operating less efficiently. 2. It’s time to schedule the rubber seals on the heat exchanger for replacement. 3. A build-up of dirt and scale so dense on the heat exchanger plates that it can only be removed mechanically.

December 11, 2015

My personal experience leads me to the conclusion that, before selecting a heat exchanger cleaning technique, one should consider all of its technical attributes, evaluate the level of fouling and the effort required. This will enable one to select the option that will allow for the gentlest possible restoration of the heat exchanger, without endangering the plates or seals with chemical reagents.

For further details on the subject, visit

How to clean a gas boiler with heat exchanger flushing

In accordance with an ancient custom, the user cleans the gas boiler on a regular basis and flushes the heat exchangers when absolutely necessary, such as when the water is completely cold or something breaks. When a master comes on call, they fix the unit, clean it, and make all the necessary adjustments for your money. The majority of gas boilers used in private residences and apartments are made in a way that permits routine manual cleaning.

When cleaning should be done

There are three possible outcomes:

  1. Preventive cleaning of the boiler is done by the homeowner himself once every 2 years with the lowest costs.
  2. The procedure is carried out as the heat exchangers are contaminated with soot and scale, which reduces the efficiency of heating and heating water for DHW needs. In this case, it is still possible to clean the boiler yourself, although calling a master is not excluded either.
  3. The heat generator has stopped due to a breakdown, which often happens during the heating season. The malfunction is eliminated by a specialist, who also cleans the heat exchanger from soot.

The last two options are obviously undesirable for the home’s owners due to the inconvenience and expense involved. If a condensing boiler with a burner and heat exchanger of a unique design is being used for heating, do not operate without a master. Going there on your own is not advised unless you are familiar with this type of heating equipment.

In conclusion, the best course of action is to perform preventive cleaning and flushing of the heat exchanger of a two-circuit gas boiler. This can be done quickly and at no cost.

How to clean the heat exchanger of the floor gas boiler

You can disassemble the heating unit at home with just an ordinary set of screwdrivers, keys, and pliers—no special tools are required. When the house is not heated, in the off-season, the heat exchanger is cleaned preventively to remove soot and scale. After turning off the gas supply beforehand, we begin disassembling the boiler by taking the burner device out in the following order:

  1. Disconnect all wires from the gas valve.
  2. Remove from the combustion chamber the thermocouple connected to the gas valve by a capillary tube.
  3. Disconnect the gas supply pipe.
  4. Unscrew the 4 nuts (or bolts) holding the stove with burner. Pull the complete assembly outwards as shown in the photo:

Cleaning the burner of the gas boiler is done without further disassembly using an old toothbrush. The igniter, the piezoelectric ignition device and the flame control sensor (if present) must also be cleaned of soot. Now it is necessary to get to the heat exchanger, for which it is necessary to remove the top cover of the boiler, disconnect the draught sensor and the chimney pipe. In the opened aperture, you will see the insulation covering the chimney casing. The insulation is carefully removed, and after unscrewing the screws fixing the casing and remove it. Underneath is the heat exchanger, from which you need to remove the steel turbulators, as it is done in the photo:

Removing the turbulators from a partially soot-clogged heat exchanger

It makes no sense to elaborate on how to clean turbulizers; all that is needed is a metal pile and an ordinary brush. However, the most effective way to clean the floor boiler’s heat exchanger is to use homemade, basic instruments that are sized to fit the smoke tubes. If their cross-section is rectangular, you will need to fashion small scrapers in the shape of scoops and a handy flat spatula out of thin metal slats.

The same tools are made slightly curved for round flame tubes. A spatula should be used to remove any leftover soot from the corners of the pipes after using a scoop to clean the walls.

After work is finished, a brush attached to a long handle can be used to sweep the heat exchanger’s entire surface. The final stage involves removing soot from the bottom, where it was deposited during the smoke tube cleaning process. This is the appearance of the heating unit’s clean heat exchanger:

In order to thoroughly examine how to clean a gas boiler at home, watch the following video:

Note: The master in the provided video went against the order of actions. He removes the soot-covered burner after cleaning the heat exchanger. This is not the proper method; take out the burner first, and then clean the soot from the flame pipes’ walls.

Cleaning soot from a wall-mounted heat generator

The majority of gas boilers that are wall-mounted can have their primary heat exchanger easily accessed. The following is the algorithm used to complete the work:

  1. Disconnect the gas supply by closing the corresponding tap.
  2. Remove the front panel of the unit.
  3. Unscrew and remove the front cover that covers the combustion chamber.

Covering the nozzles with a piece of thick paper or cardboard is necessary to prevent soot from getting into the gas burner’s holes while cleaning it, saving you the trouble of having to take the burner apart. Afterwards, use an old toothbrush to remove any soot from the heat exchanger block fins. Using a brush with a soft metal pile is an option if the stuck layer refuses to yield.

When done, use a brush to carefully remove the soot-covered sheet of paper from the interior of the unit. In the video, a wall-mounted boiler’s servicing procedure is demonstrated in detail:

Scaling of the heat exchanger

There are two methods for descaling the internal heat-exchange surfaces of gas boilers: one method involves removing the heat exchanger, and the other does not. Opting for option two is more appropriate if you plan to clean and wash your heat generator on a regular basis. It can be a tedious task to disassemble the boiler each time the heat exchanger needs to be removed. Yes, and because heaters have different constructions, some of them require almost total screw disassembly.

You will need to build your own hand flushing unit, or booster, if you want to flush the boiler without taking it apart. It’s a 15-20 liter container with attached hoses that is filled with flushing solution. Their ends are attached to the heat generator’s supply and return pipes, which activates the heating. The circulation system operates on a separate pump, just like the heating system. Having a reversible pump that can periodically reverse the direction of liquid flow is even more advantageous.

Advice: To prevent the scale from moving around the circle, place a strainer on the hose that supplies the solution from the booster to the heating unit. During the flushing process, it might need to be cleaned more than once.

Prior to cleaning the gas boiler’s primary heat exchanger, the following tasks must be completed:

  • relieve the pressure in the network to zero, using a special valve (such are in some boilers) or the Maevsky valve on the nearest radiator;
  • disconnect the heater from the system and empty it;
  • check if your model of the unit does not have a built-in strainer, remove and clean it.

A few words about how to flush the heat exchanger of a gas boiler. The most popular folk remedy, safe for all elements of the heat generator, is considered a solution of citric acid and vinegar. According to feedback from users of a well-known forum. 9% vinegar or citric acid dissolved at the rate of 20 g per 1 liter of water works well. The concentration can be increased if necessary. In addition, there are many factory-made products available for chemical cleaning of heat exchangers (e.g. Antinakipin). Flushing time is indicated on the package of the preparation, and when working with citric acid, the duration of the process depends on the degree of contamination and can take from 1 to 3 hours.

Tip: In the event that the reversible pump is unavailable, alternate the hoses periodically while working to start the liquid flow in the opposite direction. If the flow is reversed, the heating system needs to be turned off.

After flushing, replenish the tank with regular, purified water, rinse the device to remove any remaining chemicals and dirt, and then give the strainer another cleaning.

How to flush the heat exchanger of a two-circuit boiler

The kind of heat exchanger that is installed in your heat generator determines how to descal the DHW system. Only two of them exist:

  • bithermal, it combines heating of the heat carrier and water for DHW;
  • stainless steel secondary heater.

Since it can be challenging to remove the first kind of unit, it is preferable to clean it with the aid of a booster. The circulation pump and the boiler are then turned on after the hoses coming from the tank are connected in place of the cold and hot water outlets. 50–55 degrees should be the upper limit of the heating temperature.

In most circumstances, a two-circuit boiler’s secondary heat exchanger can be removed. This is accomplished by removing the front panel and then unscrewing and pushing the control unit to one side. The lower portion houses the secondary heat exchanger, which is fastened with two bolts. Following removal, it is cooked on a gas stove by submerging it in a pot of water that has been dissolved in citric acid, as explained in detail in the video:

Step Description
1 Turn off the gas supply and allow the boiler to cool down completely.
2 Locate the access panel on your boiler, usually found near the bottom.
3 Remove the access panel carefully using a screwdriver or as instructed in the manual.
4 Find the heat exchanger inside the boiler – it looks like a series of pipes or coils.
5 Use a soft brush or vacuum cleaner to remove any dust or debris from the surface of the heat exchanger.
6 If there"s stubborn dirt, use a damp cloth or brush with a mild detergent to gently scrub the surface.
7 Rinse the heat exchanger with clean water to remove any leftover detergent or grime.
8 Allow the heat exchanger to dry completely before reassembling the boiler.
9 Put the access panel back in place and secure it tightly.
10 Turn the gas supply back on and check for any leaks or unusual noises.

Maintaining the longevity and efficiency of your heating system requires routinely cleaning the heat exchanger in a gas boiler. Debris, soot, and other contaminants can build up inside the heat exchanger over time, impairing its efficiency in transferring heat. Frequent cleaning of the heat exchanger can avert possible problems like poorer heating efficiency, higher energy usage, and even system failures.

A heat exchanger can be cleaned using a variety of techniques, from easy do-it-yourself methods to more involved professional services. Homeowners can frequently handle simple cleaning chores like vacuuming or brushing away visible debris on their own for minor buildup. However, it might be required to seek the assistance of a trained technician with specialized tools for more difficult deposits or substantial buildup.

When working with gas boilers, safety should always come first, regardless of the cleaning technique selected. Turn off the boiler and let it cool completely before starting any cleaning procedures. Wearing the proper protective clothing, such as goggles and gloves, can also help avoid accidents and exposure to dangerous materials.

In addition to enhancing the effectiveness and performance of your gas boiler, routine maintenance, which includes cleaning the heat exchanger, also helps to create a safer and cozier atmosphere in your house. You may have dependable heating throughout the winter months and reduce the possibility of future, expensive repairs or replacements by being proactive and taking care of any problems as soon as they arise.

Video on the topic


Self-clean the heat exchanger of the gas boiler in 1 hour. WD-40, vinegar, burner. How and what to wash the heat exchanger of the gas boiler.

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Sergey Ivanov

I like to help people create comfort and comfort in their homes. I share my experience and knowledge in articles so that you can make the right choice of a heating and insulation system for your home.

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