Not every heating system is equipped with a professional make-up water system from the outset. Particularly in existing systems, heating water is often still topped up manually using a hose – directly from the drinking water supply, without water treatment, without documentation and, not infrequently, without a backflow preventer. Most HVAC professionals know that this is not a good long-term solution. However, when it comes to retrofitting a make-up water system, certain common mistakes continue to occur in practice – even though they could easily be avoided.
Why retrofitting a make-up water system makes sense
The reason for installing a professional make-up water system is obvious: Every uncontrolled addition of untreated drinking water changes the water chemistry in the heating circuit. Conductivity and hardness increase, the pH value can shift, and every litre introduces new hardness-forming substances and salts into the system. The result: corrosion, deposits and a gradual deterioration of the water quality that was originally established.
A permanently installed make-up water system solves this problem on a long-term basis. It ensures that every litre entering the system is treated – automatically and without manual intervention. At the same time, it enables make-up volumes to be documented, providing additional protection for the HVAC contractor in the event of a warranty claim.
But a make-up water system is only as good as its installation. And this is precisely where most mistakes occur in practice.
Mistake 1: No backflow preventer in accordance with EN 1717
The most common and, at the same time, most critical mistake is connecting the make-up water system directly to the drinking water supply without compliant protection. EN 1717 requires drinking water installations to be protected against backflow from the heating circuit. As a rule, at least a BA backflow preventer is required.
Without this protection, there is a risk that heating water could flow back into the drinking water network, with potentially harmful consequences for health. In addition, an installation without compliant backflow protection creates a liability risk for the HVAC contractor carrying out the work.
The make-up water systems in the Heaty Complete series (with the exception of the OFK devices) are equipped with a BA backflow preventer. This means that drinking water protection is ensured ex works – without additional components or installation work.
Mistake 2: Incorrect hydraulic integration
A make-up water system must be installed at the right point in the system to operate reliably. If, for example, it is installed too close to the heat generator or at a point with high flow velocity, pressure fluctuations can affect measurement and control.
The optimum position is generally on the cold return line, preferably in a section with low flow turbulence. This ensures stable pressure measurement and consistent conditions for treating the make-up water.
Mistake 3: No treatment of the make-up water
A make-up water system that merely maintains system pressure but does not treat the water being added only solves half the problem. Without treatment, every make-up cycle introduces new hardness-forming substances and salts into the heating circuit – and the previously established water quality in accordance with VDI 2035 continuously deteriorates.
All devices in the Heaty Complete range use our Vadion pH-Control mixed-bed resin. This means that every litre of make-up water is automatically demineralised and its pH value stabilised – without manual intervention and without additional equipment.
Vadion pH-Control
Our Vadion pH-Control is a mixed-bed resin that not only demineralizes the water to < 100 μS/cm (corresponding to 0–3 °dH), but also ensures that the pH value of the fill water remains within the required range.Go to the product
Mistake 4: Choosing the wrong device variant for the system size
Not every make-up water system is suitable for every application. Installing a unit that is too small for a large system can result in insufficient treatment capacity. Conversely, an oversized system in a single-family home is neither economically nor spatially sensible.
The Heaty Complete range offers the right solution for different system sizes and requirements.
Our practical calculation tool makes it easy to determine the right make-up water unit.
Mistake 5: No documentation of make-up volumes
The system is running, the make-up unit is working – but nobody documents how much water is actually being added. Yet this information is crucial: Unusually high make-up volumes can indicate a leak. And in the event of a warranty claim, proof of compliant make-up water provision can often be the only means of protecting the HVAC contractor.
Devices such as the Heaty Complete PROfessional automatically document all relevant data via the UWS Cloud Portal – including make-up volumes, timestamps and system status.
Heaty Complete PROfessional
Heaty Complete PROfessional is the world’s first smart IoT make-up system, including Cloud connection – fully automatic, leakage protection and digital water meter.Go to the product
Conclusion
Retrofitting a professional make-up water system is one of the most sensible investments for existing heating systems – provided it is installed correctly. Backflow protection in accordance with EN 1717, correct hydraulic integration, integrated water treatment and selecting a unit that is appropriately sized for the system are the key factors.
With the Heaty Complete series from UWS, virtually any existing heating system can be retrofitted – from single-family homes to commercial properties. This transforms uncontrolled manual topping-up into a permanently compliant, documented process that protects water quality and provides additional security for the HVAC contractor.
