Water Treatment

For longevity of a heating system, we need to ensure we reduce the risk of system corrosion.

Most installers will just pour in some inhibitor and hope for the best, but it requires a bit more of a scientific approach to the problem, it is important that the water is the correct pH for the materials used within the system and to reduce the conductivity of the water to reduce the risk of corrosion.

Logo_elector_EN-2014At Vietec we offer a solution from Elector, we can provide this solution for contractors, installers and homeowners on a supply and install, or we can supply the products direct to installers and contractors, for them to install themselves (we will provide technical backup) here is some more information on water quality

MP-7 water analysis equipment for installers

Central Heating Fill Water

Make-up water for modern heating systems

If you want to fill a modern heating system with water, you should not only look at the heating water for its ability to transfer the heat from the boiler to the radiator. The heating system water is much more. It is the ‘blood of the central heating’ which circulates through the pipes of the house like blood through our veins. The quality of the heating water has a massive impact on the efficiency of the heat transfer and the lifespan of the whole heating system.

Modern heating systems promise a better heat transfer and more efficiency by reduced operation costs, which comes up to our modern ecological thinking. Technological progress and new materials used for the construction are the main reasons for the energy savings, but as it is with any modern technology, it comes along with some obstacles. For their ideal function modern technology needs operational conditions which are similar to laboratory conditions.

Fill central heating with CLARIMAX

CLARIMAX 1200 HW – Water filter system for filling heating systems according to common guidelines


Why should you treat the heating system make-up water?

Modern heating systems operate much more efficiently than their predecessors. They use less energy to provide the required heat. Nowadays we use sensitive electronic sensors and control units in the heating and components which transfer the heat to the water, are much more compact and effective. The thickness of metals and the diameter of flow channels are as small as possible in order to ensure an almost loss-free transmission of the heat within heat exchangers.

When buffers are used there is a very large volume of water in relation to the heat transfer surface in the heat exchanger of the boiler. There are many dissolved salts in this huge amount of heating water that can cause problems, for example in the form of lime-scale. As the heat exchanger usually has only a small surface in proportion to the amount of interfering substances, it relatively quickly succumbs to damage.

As you may be aware, in all modern components, the possibility of malfunction rises with the increase of technical sophistication. Modern efficient products require proper handling and ideal operating conditions. In conclusion this is the demand of modern heating systems as well.

Don’t let the heating system suffer from poor quality heating water. Water is an important resource for the heating system operation!


What are the consequences of poor quality heating water?

Corrosion of circulation pump

Circulation pump of a heating system, damaged by oxygen corrosion and worse heating water quality.

If the heating water is not treated and does not meet the quality requirements, the energy efficiency of the heating usually decreases steadily. As with your kitchen kettle or other products in which water is heated, lime-scale deposits are formed. This lime settles on the heat transfer surfaces in the boiler or heat exchanger, this limits their function or even blocks their entire flow. It is reported at a lime layer of 1 mm thickness, energy losses up to 7.5%! Occur. A high content of lime (a high total hardness of the water) can limit the function of the heating heavily due to the formation of lime-scale.

Poor quality heating water can also promote corrosion in the entire heating system. In addition to damages, such as pump failures or sludge in underfloor heating or radiators, the corrosion products (rust) can also flow into the boiler and cause damage due to deposits or erosive effects of circulating particles. In view of corrosion protection in heating systems, the electrical conductivity and the pH of the heating water are important parameters and as always the amount of dissolved oxygen in the heating water must not be neglected, because oxygen ultimately is the food of corrosion.

In addition to technical problems the owner of the heating system has to expect a loss of warranty for the boiler manufacturer or other costs of expensive component failure with incorrect heating system filling water treatment. All boiler manufacturers dictate the specific heating system water quality in their warranty conditions and refer in many cases on common guidelines as recommendations.


What guidelines exist for heating system water treatment?

The British Standard BS 7593:2006 (UK), the comprehensive German guideline VDI 2035, the ÖNORM H5195-1 (Austria), the SWKI (Switzerland) and the AGFW (Working Paper for District Heating) are relevant for the treatment of heating system make-up water. The majority of the boiler manufacturers refer to the VDI 2035 as a basis for their warranty terms or take the thresholds for the water parameters from this guideline.

In addition to constructive specifications and suggestions all guidelines recommend a water quality, where damages caused by lime-scale and corrosion are not to be expected.

The British Standard BS 7593:2006 “Code of practice for treatment of water in domestic hot water central heating systems “was published in 2006. This guideline states that poor system design, ingress of air and galvanic action can promote corrosion of metals in heating systems. It is stated, that low pH, aggressive anions such as chlorides, bacteria and poorly applied water treatment products, can cause corrosion.

The Code of practice for the treatment of water in domestic hot water central heating systems claims, that for any water treatment the hardness of the raw water should be taken into consideration with reference to manufacturer’s specifications. The demand for corrosion inhibitors and use of softened filling water is clearly stated, as well as the need to clear the systems from any impurities before usage of such inhibitors.

The use of chemical inhibitors as a rule cannot be found – on the contrary the reader can find the statement, that corrosion inhibitors should NOT be used as a substitute for correct system design, installation and maintenance.

Unfortunately the current release of the British Standard BS 7593:2006 does not give any information about a water quality that supports the protection of the system against damage caused by lime-scale and corrosion, but it refers to the BSI BS EN 14868 “Protection of metallic materials against corrosion – Corrosion likelihood in water recirculation systems“.

However, newer guidelines such as the VDI 2035 give more information about a water quality that lowers the likeliness of corrosion in heating systems.
The VDI 2035 is divided into two sheets. Sheet 1 deals with the topic “Avoidance of damages caused by lime-scale in heating systems whereas the information regarding “Prevention of damages caused by corrosion “can be found in sheet 2.

With respect to the prevention of damages caused by lime-scale the claims of the VDI 2035 are really comprehensive. The allowable total hardness of the heating water is brought into context with the heating power and the amount of water in the system.

The requirements according to VDI 2035 sheet 1 are:

VDI 2035 Sheet 1 – Prevention of damages caused by limescale
Total heating power in kW Total hardness in mol/m3
Specific system volume <20 l/kW
Total hardness in mol/m3
Specific system volume >20 – <50 l/kW
Total hardness in mol/m3
Specific system volume >50 l/kW
<50 Nominal value<3.0 <2.0 <0.02
>50<200 <2.0 <1.5 <0.02
>200<600 <1.5 <0.02 <0.02
>600 <0.02 <0.02 <0.02

The first decisive role is the total heating power – the sum of all heat sources. A peculiarity of the VDI 2035 is the specific system volume. To calculate this value the heating power of the smallest heat source has to be seen in relation to the total system volume. If the result shows a specific system volume of >20 l/kW the next lower level of hardness according to the table shown above becomes valid. If the relation is >50 l/kW or if there is an electrical heating element the demand is always for a hardness of <0.11°dH.

Sheet 2 of the VDI 2035 is the guideline for protection against water side corrosion in heating systems. In summary the water quality should be as shown in the table below.

VDI 2035 Blatt 2 – Prevention of damages caused by corrosion
Low-saline Saline
Electrical condutivity at 25°C µS/cm <100 100-1500
Appearance Free of sedimentating substances (particles)
pH at 25°C 8,2-10
8,2-8,5 in presence of aluminium alloys
Oxygen mg/l <0,1 <0,02

The pH of the heating water should be in a range of 8.2 to 10, but only 8.2 to 8.5 in presence of aluminium alloys. The function of the pH in heating systems is one of the most important factors for means of corrosion protection. In the recommended pH range the metals in the system can basically build up their natural oxide layers and keep them stable to be protected against further corrosion. As long as this mechanism is not disturbed by an incorrect pH, a high electrical conductivity, a high oxygen concentration or erosion, the formation of natural oxide layers provides a safe protection of the metals against further corrosion.

The acceptable electrical conductivity in heating systems has to be seen in coherence with the amount of dissolved oxygen. If there are only traces of oxygen (y0,02 mg/l) dissolved in the heating water, the VDI 2035 tolerates an electrical conductivity up to 1.500 µS/cm. But at higher concentrations of dissolved oxygen the electrical conductivity is limited to <100 µS/cm.

It is helpful to know, that in natural waters approx. 95% of all dissolved salts are salts that affect the total hardness (carbonates and bicarbonates of calcium and magnesium). Thus one can calculate between the total hardness and the electrical conductivity. The relation 1°dH = ~33 µS/cm applies for this relation. This conversion does not work anymore, as soon as chemicals are dosed to the water or the water has been softened by an ion-exchange process. In this case ions of calcium and magnesium are replaced by sodium ions. As a result the total hardness is lowered but the electrical conductivity of the water stays as high as in the untreated raw water. Here, the devil is in the detail of water treatment. Water softening lowers the total hardness, but not the electrical conductivity and thus for a heating system with an assumable high concentration of dissolved oxygen, would be the wrong choice for heating system make-up water treatment.

With respect to heating water treatment with chemical agents the statement of the VDI 2035 is in contrast to the British Standard that such agents should only be used in limited cases by professionals with the necessary chemical education. According to VDI 2035 there is no need for chemical agents as in a well-planned operated and maintained system, with a favourable water quality, no damages caused by lime-scale and corrosion are to be expected.

The Swiss SWKI is a mirror of the strictest demands of the VDI 2035, but this guideline differs between make-up and the system water itself.

Therefore the water should meet the following requirements:

Heating water according to SWKI
Make-up water System water Unit
Total hardness <0.1 <0.5 mmol/l
Conductivity <100 <200 µS/cm
pH 6.0-8.5 8.2-10
max. 8.5 at presence
of aluminium alloys
Chlorides <30 mg/l
Sulphates <50 mg/l
Oxygen <0.1 mg/l
Iron <0.5 mg/l
TOC <30 mg/l

The SWKI advises against the use of chemicals for heating water treatment. In cases of a high concentration of dissolved oxygen the SWKI recommends the use of electrochemical methods with anodes, which can be done by use of the elector heating water conditioners.

The Austrian guideline ÖNORM H5195-1 is a less sharp guide regarding the appropriate make-up water treatment for heating systems. With respect to the electrical conductivity of the heating water it states, that the likelihood of corrosion decreases with a low electrical conductivity. Unfortunately the guideline offers no values for orientation.

General specifications according to ÖNORM H5195-1
Conductivity decreasing corrosion risk at low conductivity
Sediments and Particles <25 µm in make-up and system water
Chlorides <30 mg/l
pH 8.2-10
8.2-8.5 at presence of aluminium alloys

The similarity to the VDI 2035 is the relation between allowable total hardness, the heating power and the system volume. The Values according to ÖNORM H5195-1 are as follows:

ÖNORM H5195-1 – Prevention of damages caused by limescale
Total heating power kW Total hardness in mmol/l
Specific system volume <20 l/kW
Total hardness in mmol/l
Specific system volume >20 – <50 l/kW
Total hardness in mmol/l
Specific system volume >50 l/kW
<50 <3.0 <2.0 <1.0
>50<200 <2.0 <1.0 <0.5
>200<600 <1.0 <0.5 <0.1
>600 <0.1 <0.1 <0.1

Concerning chemical dosing for heating water treatment the ÖNORM allows the addition of chemicals to the heating water, as long as specific values are not exceeded. There is no rule in this guideline, that chemical inhibitors must be dosed to the heating water.
In summary all the guidelines are based on the following common technical requirements according to corrosion research:

  • pH of the heating water between 8.2 and 10.
  • pH of the heating water between 8.2 and 8.5 in presence of aluminium alloys.
  • A total hardness as low as possible – the higher the amount of water in comparison to the smallest heat source and the higher the total heating power the smaller the tolerable total hardness.
  • The amount of oxygen should be as low as possible, constructive action against oxygen ingress and techniques for oxygen consumption in case of constant oxygen ingress.
  • A low electrical conductivity to minimise the risk of corrosion and a low concentration of chlorides and sulphates.
  • Clean and clear water, free from sediments or organic matter.

What methods of heating water treatment are available?

Besides classic filtration of the heating water for removing particles, the most common methods for heating water treatment are

  • softening of the filling water by ion-exchange,
  • demineralisation (de-ionisation) of the filling water by ion-exchange,
  • demineralisation of the filling water by osmosis (reverse osmosis),
  • de-ionisation with pH stabilisation (CLARIMAX system).

Any of the methods mentioned above can be used for heating system make-up water treatment but each technique provides water with a different characteristics. These characteristics are crucial factors for the suitability of the water as filling water for the heating system.


What type of water does softening provide?

Device for water softening

Water softening – Lowering of the total hardness by exchange of calcium and magnesium with sodium.


By softening of filling water via ion-exchange the total hardness of the heating system make-up water is reduced.

An ion-exchanger is a filtration media, which looks a little like caviar due to its appearance. An ion-exchanger consists of small macroporous spheres which carry an ionic charge. Theses spheres are able to remove ionogenically dissolved salts out of the water or to replace dissolved salt ions with ions that are attached to the sphere.

In case of water softening a cation exchange is used. The spheres of the cation exchanger are loaded with sodium ions. As soon as untreated raw water comes in contact with the ion exchanging material all hardness salts (calcium and magnesium) are attracted by the ion-exchange spheres. The sodium ion on the sphere swaps place with the calcium or magnesium ion. The different salts exchange their position. Thus this technology is called ion-exchange.

By removing calcium and magnesium out of the water the total hardness is lowered. This basically comes up to the demands according to guidelines. But replacing calcium and magnesium against sodium ions does not lower the electrical conductivity of the heating water. In most cases the electrical conductivity of the softened water rises due to technical reasons in comparison with the untreated raw water.

This critical factor makes softened water unsuitable for heating-system make-up water, if there is a higher amount of oxygen to be expected in the heating system there would be need for water with a conductivity of <100 µS/cm.

In water with an amount of dissolved chloride ions of >30 mg/l the softening of water is not suitable for heating system filling water treatment according to ÖNORM H5195-1, as water softening does not remove chlorides out of the water. If the softener is not maintained properly the technique can even raise the amount of dissolved chlorides in the water. According to SWKI the softening of water is in general not suitable for heating system make-up water treatment as there is always the demand of a low electrical conductivity of <100 µS/cm. According to the British Standard chlorides are seen as a critical salt, thus water softening is not the ideal form of treatment if the amount of chlorides in the raw water is high.

In systems with higher temperatures, a high pH above 10 may occur, if the system has been filled with softened water. As the sodium has exchanged its position with calcium it is dissolved in the water in form of sodium-hydrogen carbonate – its partner in solution is carbon dioxide. As soon as the water is heated up above 60°C, the solubility of gases in the water is lowered and carbon dioxide changes from the aqueous to the gaseous phase. Sodium stays in the water mainly in form of sodium hydroxide which might results in a pH >10.

Due to these technical based restrictions a filling water treatment with water softening does not cover all demands of the common guidelines for heating water treatment.


Softening of heating system make-up water

By softening of the heating-system make-up water ions of calcium and magnesium are exchanged against sodium-ions. The total hardness is lowered but the electrical conductivity stays high.


What type of water does demineralisation (de-ionisation) provide?

PUROFILL deionisation cartridges

PUROFILL deionisation cartridge for lowering the total hardness and electrical conductivity of the heating system fill water.

The de-ionisation by ion-exchange follows the same principle as the water softening, but the de-ionisation of the heating-system filling water lowers the electrical conductivity and the total hardness likewise.

At the process of de-ionisation the ion-exchanger consists of two components – the cation- and the anion-exchanger.

In difference to the water softening the cation exchanger is not loaded with sodium-salts, but with hydrogen-ions. As soon as water comes in contact with the cation exchanger all positive charged ions (potassium, sodium, calcium, magnesium) change their position with hydrogen-ions.

The anion-exchanger is loaded with hydronium-ions. These swap their position with any negative charged ions in the water (carbon dioxide, silica, chlorides, sulphates, nitrates).

The treated water thus contains H+ and OH- ions – ions where water molecules are made from. The H+ and OH- ions combine to H2O – pure water.
The de-ionisation of heating-system make-up water generates a water, which has a low electrical conductivity of <10 µS/cm, a total hardness of ~0,1°dH and a neutral pH of ~7-8. All salts, even chlorides, sulphates and nitrates are completely removed from the water.

De-ionised water covers the strictest rules of any guidelines for heating-system filling water treatment and is suitable for any system situations.
But with this ion-exchange principle, the pH can cause problems. Improper use of the ion-exchanger salts of silica and carbon dioxide are not removed properly. As a result the pH of the treated water drops and the water becomes slightly acidic with a pH of 4-5. Even correct use of de-ionisation the pH can drop as soon as there is an acidic reaction in the system. De-ionised water is rather sensitive to outside influences as there are no dissolved salts that can act as a buffer against such influences.

In ordinary heating-systems without disturbing impurities and without constructive deficiency the pH of the de-ionised water normally rises to approx. 8.2 after one or two weeks of operation. This assumes that the water is heated up to >60°C and that the system is de-aerated properly so that residues of carbon dioxide can be vented. This and some metal hydroxides results in a rise of the pH.


Deionisation of heating system make-up water

By de-ionisation of heating-system make-up water all dissolved salts are exchanged agains hydrogen- and hydroxide-ions, that combine to water. The total hardness and the electrical conductivity are lowered likewise. The pH is neutral.


What type of water does reverse osmosis provide?

Reverse osmosis for heating system filling water treatment

Device for reverse osmosis for reduction of the total hardness and electrical conductivity of the heating-system filling water.Heizungsfüllwassers

By use of reverse osmosis water is pressed with high pressure through a device which contains two chambers separated by a membrane, which is only permeable for H+& OH- and depending on the operation even for some anions such as carbon dioxide, chlorides, silica and sulphates. By this membrane filtration one chamber contains pure water, called permeate, and the other chamber contains water with all salts, called concentrate.

The concentrate consists of all the salts and impurities; this water is not used for the heating system filling and is drained.

The permeate consists of pure H2O and some residues of carbon dioxide, chlorides and sulphates. The permeate provides a low electrical conductivity of <10 µS/cm, a total hardness of ~0,01°dH and a pH of around 4-6.

Due to these quality attributes water treated with reverse osmosis is used as heating-system filling water. As the pH is low from the start, special care must be taken. In most cases – as long as there are no impurities in the system – the pH in the system can rises in the same way as it rises in de-ionised water.


Deionised heating system filling water treated with reverse osmosis.

The demineralisation of water by reverse osmosis the water is pressed through a device containing a membrane. A concentrate and a permeate are created. The concentrate contains all disturbing salts, the permeate has a low conductivity and hardness and thus is used for filling the heating-system. The pH is slightly acidic.


What type of water does de-ionisation with pH-stabilisation provide?

CLARIMAX 1200 HW heating system filling water treatment

CLARIMAX 1200 HW water filter system for reduction of total hardness and electrical conductivity as well as stabilisation of the pH of the heating system make-up water.

CLARIMAX 1200 HW water filter system, for the reduction of total hardness and electrical conductivity as well as stabilisation of the pH of the heating system make-up water.

For de-ionisation of water with pH-stabilisation there are three techniques available.

The first method is based on a classic de-ionisation by ion-exchange. Behind the de-ionsation filtration is a second filter stage, containing a chemical pH stabiliser, such as trisodium phosphates. By a single time pulse dosing the amount of chemical to the water is calculated by the total capacity of the ion-exchange-filter. After mixing the de-ionised water with the chemical in the system it is possible that there is water with a low salt concentration and a pH of ~9.5. This method requires that the total capacity of the cartridge is filled into the system, otherwise the concentration of the pH affecting chemical would not be correct and the pH would be too high.

The second method is the use of special ion-exchanger resins consisting of a high proportion of anion-exchanging resin. Due to this special mixed ion-exchanger the acidic components are removed reliably. A leaking of cations through the ion-exchanger is created. Due to this leaking a small amount of calcium, magnesium and sodium-ions are not removed by the ion-exchange. As a result a water poor in salts with a pH of 8.2 – 9 is created. By use of these special resin mixtures, problems with the pH in the heating-systems are unlikely but the result very much depends on the raw water quality.

A third method is a combination of the two previous techniques, whereas the pH is not raised via pulse dosing but with a constant dosing of suitable salts. In the first stage the water is adjusted to a specific level by use of a special resin. In a second filter stage suitable salts are dosed to the water depending on the volume flow, which results in a rise of the pH. By use of a special salt-resin mixture the pH can be limited. The result is a water with an electrical conductivity of 1-100 µS/cm, a total hardness of ~0.01°dH and a pH of 8.5. Regardless of the raw water quality such filters create water that fully complies to the demands of guidelines for heating-system water quality. A product which provides such water treatment is the CLARIMAX 1200 HW water filter system.

Deionisation and pH stabilisation of heating water

The de-ionisation of the heating-system filling water with pH-stabilisation replaces all dissolved salts with hydrogen- and hydroxide-ions, which combine with water. The total hardness and the conductivity are lowered likewise. A salt is added to the water which rises the pH to a specific level.


Why can the system water quality differ from the make-up water quality?

corroded heating pipe

Old residues in the heating system can change the quality of the new filling water as soon as these two elements come in contact.

Even if the filling water treatment provides water according to common guidelines the system water depends on the residues and impurities in the system. Especially older systems with residues of chemicals, hardness salts, sludge of rust and lime, old water and other matter can cause a huge difference between the filling and the system water.
With older systems one should always be aware of the following points:

  • Before refurbishment, the water of the old heating system should be analysed. The result helps to consider about possible negative influences of the old water onto the new water quality.
  • Especially by use of de-ionised or reverse-osmosis water there can be huge differences between the make-up and the system water.
  • In new systems there are less residues, thus the system water normally is equal to the make-up water quality.
  • Old residues can have an impact on the electrical conductivity, total hardness and the pH of the new water.
  • Careful cleaning of the system before refilling can be necessary, as well as water correction after refilling.

The awareness of the inconstancy of the water is an important factor, which should not be forgotten to sustain possible warranty claims.
Along with other factors this is why a water analysis of the heating water should always be done four weeks after putting the new system into operation. During this time the heating water quality can change drastically during ongoing operation.

As well as residues the construction of the system can have an impact on the water quality as well. If there is a constant ingress of oxygen or carbon dioxide, the water quality can change constantly. The awareness of the inconstancy of the water is an important factor, which should not be forgotten to avoid possible warranty claims.


What effect does dissolved oxygen, carbon dioxide & nitrogen have in the heating system?

Corroded microbubble separator

A Micro-bubble separator lowers the total amount of dissolved oxygen in the heating system. Corrosive water can damage even separators so that they cannot provide proper system deaeration.

With respect to the oxygen concentration in heating systems all common guidelines suggest it is best to install sealed systems only and to reduce the oxygen ingress down to zero by the choice of diffusion resistant materials and ideal operation mode. If no oxygen ingress takes place the oxygen corrosion will cease quickly even if the electrical conductivity is at a high level.

In most cases malfunctions are of pressure maintenance, plastic materials such as non-diffusion protected underfloor heating pipes, seals or dirt separators made from plastics material are the main sources for oxygen ingress. These sources are often found in older heating systems. In such systems it is only a question of time that amount of oxygen ingress will cause failure. As oxygen is known to be the food for corrosion such heating system are exposed to a high risk of corrosion.

Good methods of oxygen consumption and ideal water quality can make constant oxygen ingress tolerable, so that even such systems can operate without corrosion related problems.

With oxygen ingress the ingress of other gases will occur, such as carbon dioxide and nitrogen. Both can have a big impact on the operation of the system. Nitrogen can cause air cushions, erosion corrosion or can lead to noises. Carbon dioxide has an influence on the pH. In the presence of carbon dioxide, the pH of the water can drop to a slightly acidic level, this will be dependent on the temperature and usually occurs in the cooler water zones, such as the main return. This carbon dioxide influenced pH-drop can cause corrosion in the main return of heating systems.


What actions does elector recommend for an ideal filling- and system-water quality?

The quality of the heating system make-up water and of the heating system water itself is subject to changes which are sometime unavoidable Heating water quality according to common guidelines has to be seen as preventive action against damages caused by lime-scale and corrosion and to prevent the loss of warranty. The result of heating water treatment requires well considered methods.

We have gathered positive experience with chemical free operation of heating systems since 1991 and recommend the following action for filling heating systems with treated water and their operation according to common guidelines for heating system water quality.

Pressure maintenance for heating systems by correct dimension of expansion vessels.

Pressure maintenance and system operation parameters

The lowest possible system pressure with functional pressure maintenance, not too high temperatures and a moderate flow rate are the main conditions for an uncomplicated and failure free system operation.

Heating water analysis

Heating-water analysis in advance

In cases of system refurbishment and even new systems the heating-water analysis can be a helpful tool. a system-water analysis helps find the conclusion to see if the existing water in the heating system or the tap water quality makes water treatment necessary, or if some methods of treatment are excluded. A heating water analysis can act as proof for successful heating-water treatment.

Heating system cleaning agent OXILIN-P20

Disposal of impurities from existing systems

Systems with old components should be checked, old impurities & remains of old water can have a negative effect on the new water quality in the heating system. In many cases we suggest to clean and flush the heating with a dispersing and cleaning agent, such as OXILIN-P20.

CLARIMAX for heating system filling water treatment

pH-stable deionised make-up water

In general we recommend the CLARIMAX water filter system for make-up water treatment. CLARIMAX produces water low in salt with a low hardness and low conductivity, but with a pH of 8.5. CLARIMAX provides you with ideal filling water for any heating system according to common guidelines and is an ideal make-up water treatment solution for any system situations.

Stainless steel deionisation cartridge for heating system filling water treatment

Deionised (demineralised) water for refilling or larger systems

Unfortunately the CLARIMAX water filter system is not an economic solution for refilling a heating system or for initial filling of large systems. In such cases we recommend the use of regular deionisation systems, such as PUROFILL, by use of special mixed bed resins, designed for heating systems make-up water treatment. By use of such resins the pH does normally not drop <7 within the capacity range.

Deaeration of heating system with microbubble-separators

System de-areation

Both in new and old systems correct de-aeration is necessary for stable system water quality. This can be done by use of microbubble separators. With de-aeration of the system, the remaining carbon dioxide can be vented and thus the pH can rise to a preferable level.

CLARIMAX for filling heat pump systems

Filling of low temperature systems with CLARIMAX

Especially suited to low temperature systems, such as heat-pumps, with these systems the pH cannot raise with venting off carbon dioxide. The necessary temperature level is not achieved in such a systems. Thus filling such systems with CLARIMAX is the best solution as the pH is already within a preferable level in the filling water.

Deionised water for filling heating systems

Mix the filling water

As long as the system situation does not require a complete removal of the water hardness, we recommend filling with a mixture of deionised water and raw mains water into the system. A mixture of 80% deionised water and 20% raw mains water provides a heating system filling water low in salt, with low hardness and low conductivity. The remaining water hardness can act as a buffer against acidic reactions and stabilises the pH.

Water analysis for system water correction

Correction of the system water (only if required)

For systems with old parts or even in some cases new systems a correction of the system water might be necessary. In such cases a de-ionisation of the circulating water can be helpful. In some cases the manual adjustment of the water with special water treatment agents may be necessary. In all cases the water should be analysed before and after such corrections of the system water.

elector XS5 for corrosion protection in heating systems

Electrochemical heating water conditioning

In systems with old components and / or ingress of oxygen we recommend the use of electrochemical heating water conditioning with our elector-devices. This technology meets the recommendations of the guideline SWKI (Switzerland) for oxygen consumption. The electrochemical method is an ideal combination to water which is poor in salt, as it keeps the conductivity low, stabilises the pH at a level of >8.3 – 10 and consumes dissolved oxygen constantly.

Whatever the method for the treatment of heating system filling water is, the success is always a question of experience and the correct combination of possible methods. elector is not only provider of water treatment solutions but an adviser and partner at your side.

Elector XS5

Corrosion-protection device for heating systems up to 0.5 m3 system volume

The corrosion-protection device elector XS5 is suitable for use in central heating systems or similar closed water systems with a water volume up to 0.5 m3.

By combination of proven technologies in one appliance the elector XS5 is an ideal safety device of central heating systems for water side corrosion without the addition of chemical corrosion inhibitors.

Main function of the elector XS5 is an electrochemical water-treatment, which results in an increase of the pH-value, in a constant oxygen consumption and in a clarification of the system water. A cyclonic water flow and separation plates installed inside of the elector enhance the separation of impurities and the venting of the heating system by an air-vent. In addition, a strong magnetic filter rod of rare-earth provides the effective removal of magnetic particles from the heating water.

In conclusion the usage of an elector XS5 means:

  • Separation of circulating impurities from the system water by a cyclone effect and separation plates
  • Separation of magnetic particles by a strong magnetic filter rod
  • Clean and clear system water
  • Reduced conductivity of the heating water
  • Stable pH >8.3
  • Constant oxygen consumption und deaeration, resulting in an decrease of the oxygen content in the entire system
  • Protection of the metals in the system by a water quality which supports the formation of natural protective layers and passivation (corrosion protection)

The electrochemical water treatment is a well known method for an eco-logical corrosion protection in central heating systems and is a recommended method for refurbishment and protection of central heating systems in case of water containing oxygen resulting in corrosion. (see Swiss guidline SWKI). The increase of the pH-value by electrochemically formed hydroxide is state of the art technology and a safe way to operate a central heating in combination with demineralised water in a low-salt operation style according to VDI 2035.

The elector heating water conditioner offer a proven corrosion protection for maintaining the central heating and are an ideal safety device especially for older heating systems after flushing, for example with the cleaning and dispersing agent OXILIN-P20 for protection from the formation of new sludge.

Product Features


Technical Data
Application area: Water Conditioning for corrosion protection in heating systems
Working temperature: max. 90°C
Operational pressure: 3 bar
Test pressure: 6 bar
Vessel material: Stainless Steel 1.4301 (V2A)
Insulation: Foam insulation with pvc-cover, white
Shipment: – elector XS5 corrosion-protection device
– Connecting kit
Installation instruction: The device is for installation in full-flow (return or flow). Please pay attention to the elector user manual.
elector model System volume
(without buffer storage)
Heating power estimated* Assembly ~max flow rate m3/h Δp at ~max. flow rate [kPa] Article
elector XS5 0.5 m3 ~18.5 l/kW UFH
~12 l/kW Radiators
Wall 2.4 4.68 14010

*Please add approx. 20% to the heating power in case of old heating systems with new heater

elector XS5 dimensions

Dimensions (mm)
A Diameter 170
B Distance container – Wall 92
C Total height 500
D Height container 315
E Centre bracket – centre inlet horizontal 47,5
F Centre bracket – centre outlet horizontal 47,5
G Centre Container – centre inlet / outlet vertical 37,15
H Distance (recommended) 200
Inlet bottom, Outlet top 1″


Text for invitation to tender

Corrosion-protection device elector XS5

Electrochemical water treatment for corrosion protection in central heating systems. Function without external energy or chemical additives for the constant consumption of oxygen, increase of the pH-value to an alcaline level according to VDI 2035, cleaning and purification of the system water, prevention and removal of sludge, corrosion protection by formation of natural layers in the system.

Container made from stainless-steel with integrated magnesium electrode and function control instrument, separation plates for removal of suspended solids, neodym magnetic
filter rod for removal of magnetic particles.

Operating pressure max. 3 bar
Temperature max. 90°C
For heating systems with ≤0.5 m³ volume
(without buffer storage)

Foam insulation with pvc-cover, white and zipper, Thickness 30 mm
Automatic air-vent, draining valve, opening for inspection and cleaning, including connection kit with all
necessary fittings.

Installation in full flow return or flow of an central heating.

Manufacturer: elector GmbH, Germany
Model: elector XS5
Article-no.: 14010

Clarimax 1200 HW

View this PDF for more details



View this PDF for more details