What does VDI 2035 tell us about preventing corrosion in closed water systems?

22nd May 2023

VDI 2035 is a German standard that provides guidance on how to prevent scale and corrosion in heating and cooling systems and use monitoring to ensure treatment is effective.

It’s non-additive approach to chemical water treatment is widely used in Germany and, increasingly, it is also being adopted in the UK alongside BSRIA BG50.

Crucially, both BG 50 and VDI 2035 recommend remote monitoring as a method of detecting adverse water conditions that could lead to corrosion, inefficiency and system failure. Whilst also being indicative of poor maintenance practice or unplanned remedial works resulting in water loss and chemistry adjustment.

What is VDI 2035?

VDI 2035 is a set of guidelines developed by the Association of German Engineers (VDI) for the treatment of water used in heating and cooling systems. The full title is “VDI 2035 Blatt 1: Scale formation in water-bearing systems – Reduction of the risk of damage”.

The guidelines provide a framework for water treatment in closed heating and cooling systems to prevent scale formation and corrosion, which can cause damage to pipework and components and decrease system efficiency.

What is the difference between VDI 2035 and BG50?

VDI 2035 and BG50 are similar in that they both set out guidance for facilities managers (FMs), design engineers, installation contractors and maintenance staff on effective water treatment for closed-circuit HVAC systems to ensure efficient operation.

Both documents draw particular attention to oxygen and its role in the corrosion process. However, VDI 2035 focusses on fill water quality and reducing oxygen ingress, recommending chemical inhibitors only as a last resort.

Furthermore, Building Managers should be aware of the requirements of capital equipment and installation materials where low conductivity water treatment is recommended.

Are chemical water treatments necessary?

The use of chemical inhibitors is common in the UK and can be very effective at preventing corrosion in closed circuit systems. However, if poorly managed or over-specified, chemical water treatments can exacerbate the issues they were intended to resolve.

It is important to choose the appropriate type and dosage based on the specific system requirements and water conditions. Common types of chemical inhibitors include corrosion inhibitors, which form a protective layer on metal surfaces, and oxygen scavengers, which remove dissolved oxygen from the fluid.

One of the key benefits of remote HVAC monitoring is that chemical interventions can be planned and informed, avoiding potentially damaging flushing and dosing that may historically have been used as a routine step. With real-time data to hand, FMs can utilise alternative technologies, such as side stream filtration and non-chemical treatments, alongside traditional methods when necessary.

How do you meet the guidance set-out by VDI 2035?

If the aim is to use chemical treatments only as a last resort, close and regular monitoring is critical. VDI 2035 recommends that closed circuit water systems be monitored for parameters such as pH, conductivity and dissolved oxygen.

The frequency and method of monitoring may vary depending on the type of system and the specific treatment methods used, but the guidelines recommend that monitoring be performed regularly to ensure that the treatment is effective and that any necessary adjustments can be made in a timely manner.

BG50i from Guardian Water Treatment – intelligent monitoring and maintenance 

Our BG50i intelligent monitoring and maintenance package utilises real-time data from Hevasure’s award-winning 24/7 monitoring system, which tracks a range of parameters in order to get a real-time view of system integrity, water characteristics and corrosion, including:

  • Dissolved oxygen
  • Pressure
  • pH
  • Conductivity
  • Temperature
  • Inhibitor/glycol concentration
  • Steel corrosion rate
  • Crevice corrosion

BG50i provides clarity and control, and a greater understanding of the corrosion process and how it can be mitigated, supporting FMs and responsible parties who choose to take an effective low conductivity/low oxygen approach to managing closed systems.

Find out more about BG50i for your HVAC system