Is the heating in your house getting noticeably worse? The boiler has to be turned on to maximum and your gas bill is steadily increasing? Don't rush to repair and replace your boiler or radiator heat exchanger - flushing your gas heating systems gets rid of such problems in most cases.
This relatively inexpensive procedure will extend the service life and increase the efficiency of each system link, avoid or significantly postpone costly repairs. From this article you will learn about the different methods of flushing the heating system, their advantages and disadvantages. We will also tell you how to understand when flushing is necessary, how to perform it yourself and, what to do so that the system clogs much less.
Content of the article:
- When is it necessary to flush the heating system?
- Mechanical cleaning
- Rinsing from the tap
- Hydrodynamic flushing
- Pneumatic cleaning
- Rinsing each part with disassembly
- Chemical cleaning methods
- Electric water-pulse cleaning of heating systems
- What to fill the system after the flushing?
- Conclusions and useful video on the topic
When is it necessary to flush the heating system?
The heating system flushing procedure is mandatory in heating system maintenance and its procedure is clearly regulated by SNiPs and PRRFs. Norms recommend annual flushing, but this only applies to central heating systems.
These systems are large-scale and multi-component, consisting mainly of steel pipes of solid age, and the coolant is frequently refilled and not always sufficiently cleaned. A combination of these factors makes annual flushing justified and necessary.
But private heating systems serving a single-family home or apartment operate under different conditions and therefore should be flushed as needed, not annually.
Home boilers usually use plastic pipes and modern radiators and eliminate leaks and the need for regular refilling - this significantly reduces the amount of deposits
Determine that the system needs flushing by these signs:
- The radiator heats unevenly: some sections or the lower part is much colder.
- The steel supply pipes are much hotter than the radiators.
- The whole system heats slower than before.
- The gas consumption increases, the mechanically controlled boiler has to be set on high load more often.
- Unusual sounds in the boiler or in any part of the system.
- Filter installed in the return is regularly clogged.
Even if you have all the described signs, flushing is not always necessary - system clogging has the same symptoms, and is corrected much easier - through the Maevsky valve or a special valve. Therefore, first of all, exclude the possibility of air lock in the cold part of the radiator, and only then choose the method of cleaning.
If you neglect the timely flushing of the heating system, you risk not only to overpay for gas. Accumulating in the heat exchanger of the boiler, solid particles overheat the metal and provoke its burnout. In addition, plaque can disable the circulating pump, expansion tank, boiler, and cause leaks.
Without flushing the pipes can become completely overgrown with plaque and rust, and the boiler will become a dead end. Getting such seals in the pump leads to failure
On the other hand, too frequent flushing, especially with chemicals, can do more harm than good. First, the inside surface of the piping and all connections wear out faster. Secondly, fresh coolant carries a new batch of salts and air, which provokes a new wave of corrosion.
The systems with plastic pipes and aluminum radiators are least likely to need cleaning, because they do not form rust. However, they cannot exclude lime scale and therefore it is not worth forgetting to rinse completely.
Mechanical action on deposits is safer for the pipes than chemical cleaning, but it is not always possible to flush the system to a clean metal condition using these methods. Nevertheless, mechanical cleaning is popular because of its availability and effectiveness for not too dense plaque, in private networks it may be quite sufficient.
The main thing when cleaning yourself is not to do any harm. Do not disassemble the system unless you are sure you can reassemble it without leaks, and when choosing a flushing agent, strictly follow the materials and recommended exposure times.
To diagnose and locate a clogged heating system more accurately, use a thermal imager or pyrometer, and open the circuit to assess the type of deposits
The choice of flushing depends on many factors:
- The material of radiators and pipes. Steel forms hard rust, cast iron has a dark oily buildup, plastic can only have lime buildup or slime at low pressure and temperature, such as underfloor heating.
- Pressurized or gravity circulation of the coolant. The higher the pressure in the system, the less deposits on the walls, and the denser they are.
- The type and thickness of deposits - it is easy to determine after opening the system.
- The age of the system and the time of the last flushing. Up to 3-5 years old even rust is quite loose and easily removed.
- The presence and condition of filters.
- The location of the boiler and the features of the system structure: presence of indirect heated boiler, complex shaped piping, total length of piping, etc.
Consider all these parameters of your particular system, diagnose with a thermal imaging camera and choose the most efficient method of cleaning can be done by specialized service personnel.
Flushing from the tap
The easiest flushing method is to open the heating circuit and run water through it from the tap. To do this, shut off the water supply and water outlet taps from the boiler, shut off the expansion tank.
Then drain the coolant through a special valve in the return line, preferably into a prepared container. If it is planned to use it again, the coolant must be carefully filtered.
The radiator in the apartment can be washed only if there are taps in the places where it is connected to the riser, and during the heating season the bypass is also needed
One hose is connected between the water tap and the beginning of the heating circuit, at the boiler outlet. The second hose leads from the discharge valve to the sewer.
Open the water tap to the maximum pressure and watch what flows into the sewer. When the water is clear at the outlet, cut off the water supply.
For greater efficiency it is recommended to reverse the hoses and flush the system in the opposite direction and then repeat the procedure again, but in the opposite direction.
In the last flushing the water supply is not cut off, but only reduced and the expansion tank is opened. Then the discharge hose is removed, the valve is closed and the system is topped up to the desired level. Only then turn off the water supply and connect the boiler to the circuit.
The effectiveness of this flushing method depends on the type of contaminants and the head in the water supply. If you have water flowing softly and smoothly from the maximum open faucet, such cleaning is practically useless. Among its indisputable advantages is the possibility to flush by oneself, without special equipment, and to discharge the waste directly into the sewer.
This method requires special equipment but is one of the most effective and safe.
A hydrodynamic head is inserted into a pipe or radiator and applies pressure directly to the accumulation of plaque. The method is not very popular because it requires opening the circuit in several places
The essence of the method is the use of a special head on a flexible hose forming thin high pressure jets inside the pipe or radiator. Water is pumped into this head through a pump and the nozzle is inserted into the heating circuit break. In general, the principle is similar to a car wash.
This method can safely wash the most problematic and hard-to-reach areas - such as the bottom and middle sections of a large radiator. It is suitable for any material and type of contamination, and the washing waste is absolutely safe. Spot action allows you to wash any surface to metal without the use of chemicals, and to stop more thoroughly in the areas of greatest contamination.
The disadvantages of the method are the necessity to open the heating circuit, to arrange for the drainage of the sewer, as well as the need for special equipment and the limited range of the head.
Cleaning with pneumatic tools
Compressed air from a compressor is often used to clean anything, including the heating system. This option is safe and efficient and therefore popular.
It is possible to blow out the whole system at once, in forward and reverse direction, or its individual sections, having previously dismantled them. The second option is more labour intensive but more effective especially in systems of considerable length.
For cleaning the radiators a compressor can be connected directly to the radiators either through special equipment mixing air and water or using a blowing gun
The cleaning is not done by constant air pressure but by short pulses of maximum pressure and if possible by changing the angle of the pipe. Before filling the system with constant coolant, it must be flushed with clean water to remove all particles dislodged from the walls.
In addition to turbulent compressed air flows in empty pipes, hydro-pneumatic flushing is also used. Its key difference is that air is fed into pipes filled with coolant. As a result, bubbles are formed, water bubbles in the system, washing all deposits off the walls. Such flushing is effective even in large systems of apartment buildings, and due to the low cost of consumables it has become very popular.
Hydropneumatic pulse flushing involves feeding a mixture of compressed air and water with a series of short jolts, using a pneumatic gun. After 60 m of piping, or when the diameter is greater than 4 inches, the jolts lose their velocity and thus their destructive power to the plaque.
This unit will help clean the most clogged areas as the velocity of the mixture delivered reaches 1300 m/s, but is effective for relatively small areas
But in private heating systems it is the hydro-pneumatic pulse cleaning that gives the best results by evenly cleaning the entire system in a short time. In addition, no toxic waste is left behind and the pipes are not damaged.
Dismantling each unit
If you have decided to flush the heating system in the best possible and safest way without the help of professionals and special equipment, it is better to completely disassemble it. In a private home it is convenient to flush everything outside, so choose a warm clear day.
In autumn, shortly before start-up, dismantle the radiators, pump, expansion tank, if any - disconnect the indirect water heater and other equipment. Remember where which gasket was, or better yet, buy new ones to replace them. Arm yourself with hoses with adapters, a rope for cleaning drains, a long brush with metal bristles, possibly a metal brush for a grinder, if available - a pump.
First try to clean off as much sediment as possible with a rope and brushes. Unscrew all plugs from the radiators, clean all holes and joints, every thread. Run a wire and twist it well to wipe all the walls. It is convenient to clean the pipes with the pipe cleaner, the handle can be extended with a stiff wire.
Metal brush or a grinder with such nozzle is convenient for the ends, connection points to the heating circuit or to install plugs
With each element cleaned, flush it with clean water, connect a water pipe and plug the extra holes in the radiators. Run the water pressure in both the forward and reverse directions. Repeat the cleaning with a tether and brushes, and rinse again. Repeat the procedures until clean water flows immediately after cleaning.
Don't forget to flush the boiler coil, just don't use brushes in it. If there has been a lot of hard plaque on other parts of the system, clean the coil with a cable and then flush by connecting two hoses.
Reassemble and fill the system with coolant and check all connections for leaks.
Chemical cleaning methods
The most impressive results are obtained using chemical compositions, in addition this cleaning is the least time consuming. However, most flushing products for heating systems with gas boilers are based on acids, which can destroy not only plaque but also metal.
This method of cleaning is therefore used where others will fail, and as infrequently as possible.
Chemical cleaning restores pipes virtually to new condition, some compositions will also provide protection for 1-3 seasons, but in the most damaged areas the leakage may open
Check the following points when choosing a chemical cleaner:
- Compatible materials. Owners of aluminum radiators should be especially careful - most compositions for them are not allowed, but specialized solutions exist.
- Proportions and time of use. Putting too concentrated a solution in the system, or for too long, will surely damage it.
- Type of deposits. Remember, the more types of deposits a product can remove, the more likely it is to damage pipes, radiators, gaskets at joints.
- Necessity of disposal. Many compounds are forbidden to pour into the sewer, and the collection, removal and recycling of such a volume of liquid can be a problem.
How to apply the composition for chemical cleaning of the heating system is described in detail in its instructions. In most cases it is necessary to drain the coolant, prepare a solution of the same volume of water and reagent, mix well, pour it into the system and run it.
As a rule, the composition should circulate through the circuit for 2 to 24 hours, after which it must be drained and the entire system flushed with clean running water and filled with new coolant.
Please note that the coolant with the reagent should always be force-fed through the system under pressure - i.e. via a pump.
The chemical flushing of a single section requires a special pump with a container which ensures a small circulation range with hoses
A part of the heating circuit including a boiler heat exchanger can also be flushed with the reagent. It is desirable in this case to flush in the opposite direction to the normal course of the coolant.
For varieties of chemical cleaning, it is worth to distinguish microbiological and dispersed cleaning. They differ only in the compositions used: In the first case they are of biological origin and do not require special disposal.
Dispersed washing is a new, advanced technology in which the bonds of the sediment particles are destroyed and the metal does not react.
Dispersed washing forms a film inside the pipes and radiators, preventing metal contact with water and its oxidation, and reducing the friction resistance. According to the manufacturers this film lasts for 3 seasons, which means that during this period your heating system will not get clogged.
Electro-hydro-pulse cleaning of heating systems
This is another method of professional heating system cleaning in which pulse cleaning devices are placed in a pipe filled with water. Even the most neglected pipes can be cleaned with this method regardless of the difficulty of shape and bends at a speed of 1-8m per minute.
This method is used more often for industrial heat exchangers but has also proven its effectiveness in private heating systems
This method cleans pipes completely, down to the metal or plastic without damaging them. It is safe for equipment of all materials, the consumables are inexpensive and the waste is absolutely safe. This method perfectly removes limescale, salt and lime deposits, but is powerless against rust.
What to fill the system with after flushing?
After you have flushed the heating system and have seen how many various deposits it contains, the choice of a new coolant becomes particularly critical. It should contain a minimum of impurities of salts and calcium, microorganisms, as well as air, because all this provokes corrosion and forms a deposit on the walls of pipes and radiators.
Filling the heating circuit directly from the water supply is probably the worst choice. It is often too hard, that is, with an abundance of salts of various metals. In addition, it carries all the dirt from the pipes of the central water supply, and is so oxygen-rich that it sometimes turns white - at high pressure.
In order to use such water for the heating circuit, at least it should be allowed to stand for a long time, so that all the gases, including chlorine, will air out and the solid particles will settle to the bottom. Besides it would be good to pass it through a filter.
Dismantle and flush the radiator clean and do not fill it with impurities, otherwise you would need to flush it again next year
As an alternative you can use rain water, as it is soft and available. However, sedimentation or filtration is still a must. In addition, microorganisms often multiply in rain water, which can affect the radiators in a bad way.
A good choice is distilled water, because it does not contain absolutely any precipitating impurities. In addition, such a choice is not cheap, because the volume of the heating system is not 5-10 liters, but dozens of times more.
Uddly enough, one of the best options is the old coolant drained from the system before flushing. All the impurities that might have reacted with the pipes and deposited on the walls have already done so, and the air is out during operation.
It is enough to filter it well to remove particles washed off the walls of the pipes, and you can add to the desired level distilled water - in this case it will need very little.
Dark coolant is not always unsuitable for reuse - the color indicates only that it has already reacted with the metal
It is sometimes recommended to fill the heating circuit with anti-freeze with special additives against rust. Indeed, such coolant does not form a scum, but it is expensive, and its heat capacity and heat output are worse than those of water. As the result by pouring such expensive heat-transfer agent you would pay more for gas as the system would not work so effectively.
With this in mind the antifreeze can be recommended only if the heating is not used constantly in winter and there is no possibility or wish to pour out the heat-transfer agent every time. You can read more about the different types of coolant for heating systems in this material.
Conclusions and useful video on the topic
See how to flush a heating system consisting entirely of underfloor heating can be seen in this video. The chemical method of flushing is not chosen by chance, because other options are almost impossible to implement with so many pipes, connections and bends:
Cleaning an individual radiator by hydro-pneumatic method is shown and described here:
When choosing a flushing method for your heating system, try to balance convenience, price and safety for both pipes and the environment. Remember, you are the only one who can live with the system and repair it in the years to come.
Are you flushing your heating system often? Do you use professionals or do you do it yourself? What flushing method do you prefer? Join the discussion in the block below the article.