A new heating system does not automatically mean clean heating water. What is often underestimated is that significant contamination can already be present in the pipework before the system is filled for the first time – and this contamination becomes a problem if it is not removed before commissioning.
Metal swarf from cutting pipes, flux residues from soldering, thread sealants, sand, dust and other construction debris inevitably enter the pipework during installation. If the system is filled without prior cleaning, these particles are distributed throughout the entire system – and can reach components that are particularly sensitive to contamination: heat generators, pumps, mixing valves and heat exchangers.
What happens if the system is not cleaned?
The consequences do not always become apparent immediately, but they are well documented in practice.
Metal particles such as copper or steel swarf can accumulate on sealing surfaces and inside valves. In combination with the system water, they can also trigger electrochemical corrosion processes – precisely the type of damage that compliant heating water treatment is intended to prevent.
Flux residues are particularly critical. They generally contain aggressive substances that can alter the pH value of the heating water and significantly increase its conductivity. The result: the water chemistry becomes unbalanced before the system has even entered normal operation. Even subsequent treatment with mixed-bed resin may then be unable to achieve its full effect, because the contaminants unnecessarily consume resin capacity or distort measurement results.
Sand and dust, meanwhile, settle in areas with low flow and can form the basis for sludge deposits – a problem that is much more difficult to eliminate once the system is in operation.
What do the standards and guidelines say?
VDI 2035 requires water quality in heating systems to continuously comply with the specified guideline values. DIN EN 14336 also explicitly states that pipework systems must be flushed before commissioning if it cannot be ensured that the system is free from contamination.
In practice, this means that cleaning is not an optional additional step, but a prerequisite for a compliant initial filling. Skipping this step can result not only in system damage but, under certain circumstances, also in the loss of warranty claims against the manufacturer.
How to clean the system correctly
1. Flush the pipework system
Before the actual filling process, the entire pipework system should be thoroughly flushed. The objective is to remove loose particles, metal swarf, sand and dust from the system.
It is important that all branches and heating circuits are flushed individually. Simply flushing through the main pipe is often not sufficient to reach remote sections of the system.
2. Chemical cleaning in the event of heavy contamination
If stubborn residues are already present – such as dried-on flux residues or oxide layers on pipe surfaces – simple flushing may not be sufficient. In such cases, targeted chemical cleaning with Heat Clean is recommended to dissolve contaminants and subsequently flush them out in a controlled manner.
3. Check water quality before initial filling
After cleaning and before the actual filling process, the relevant water parameters should be checked.
With the WaterBoy measuring case, the pH value, conductivity and other parameters can be analysed directly on site and documented using the WaterBoy app.
4. Compliant initial filling and water treatment
Only after successful cleaning should the system be filled with treated water, or with drinking water followed by treatment via a bypass process.
In practice, a particularly time-efficient approach has become established among HVAC professionals: The system is initially filled with standard mains or drinking water, which is then treated using the bypass process.
The major advantage is that the treatment unit operates independently within the circuit. The installer does not have to remain next to the system and monitor the entire process, allowing them to carry out other work on the site in the meantime.
For mobile on-site bypass treatment, the Heaty Ferriline No. 2 and Heaty Profiline No. 2 are suitable solutions. We also offer solutions for stationary installations that operate fully automatically.
In all cases, Vadion pH-Control mixed-bed resin provides targeted demineralisation and automatic pH stabilisation – the basis for long-term stable water quality in accordance with VDI 2035.
Cleaning as part of the overall system concept
Initial filling alone does not determine the service life of a heating system. But it lays the foundation. And that foundation does not begin with the first litre of treated water – it begins with a clean system.
By consistently integrating site cleaning into their workflow, HVAC professionals create the best conditions for reliable operation, stable water parameters and satisfied customers. At the same time, they document a professional installation process that can make a decisive difference in the event of a warranty claim.
Conclusion
Metal swarf, flux residues and construction dust have no place in a heating circuit – and yet they can enter the system during almost every new installation unless active measures are taken to prevent this. Proper system cleaning before initial filling is therefore not an additional burden, but an investment in system reliability and longevity.
With the right solutions – from filtration and cleaning through to compliant water treatment – this process can be implemented efficiently and reliably. This ensures that every heating system starts operation under optimal conditions.
