What is VDI2035, and why do I need it?

VDI2035 is a set of water quality guidelines for heating water developed in 2009 by the Association of German Engineers. The equivalent in the UK would be BS7593; however, the construction industry widely accepts that the VDI2035 is based on stronger scientific evidence and is much more in-depth. Compared to the VDI2035, the UK’s equivalent set of regulations for heating water is quite brief and vague. Many engineers argue this leads to an inability to interpret or follow proper health and safety guidelines. In addition, professionals recognise the VDI2035 as a set of corrosion preventative measures within water-heating systems. In contrast, the methods commonly employed in the UK are typically a reaction to existing corrosion. Traditional UK methods use potentially harmful and unnecessary chemical inhibitors.

What doesVDI2035 include?

There are three important parts to the VDI2035, outlined below:

Part 1: Scale Formation in Drinking water and Water Heating System

Scaling occurs within plumbing systems when the water has particularly high levels of minerals like calcium carbonates. Over time calcium can build up over time and cause long-term damage to your pipes and boiler. Due to scaling, problems that can occur may include the reduced efficiency of your boiler, reduced or blocked flow to your fixtures or appliances, and leaky valves.

To prevent the formation of scaling within your pipes, the hardness of your water must be below 200ppm of mineral concentration. Part 1 of VDI2035 recommends a comprehensive demineralisation of the fill water for a closed water heating system.

Part 2: Waterside Corrosion

Waterside corrosion happens to a water heating system, such as your boiler, when high temperatures cause oxygen and acid to dissolve in the water. If uncontrolled, waterside corrosion can lead to severe pitting, pinholing, and embrittling of the tube metal. Such damage will eventually lead to the breakdown of your water heating system.

Part 2 of VDI2035 applies to systems where the flow temperature of the water is less than 1000 C˚. In addition, over the service life of a system, the volume of make-up water will not be more than three times the volume of the initial make-up water. The guidelines recommend a professional planned system. The system prevents oxygen corrosion without using chemicals during the operation of the water heating system. Part 2 of the VDI2035 highlights that oxygen levels will be reduced and maintained at a low level. The low level is acheived by the correct start-up of a plant, decoration, proper pressure maintenance, and the design of a system preventing oxygen ingress.

Inhibitors are chemicals used to protect the lifespan of your heating system. This section also highlights that inhibitors should only be used as corrosive protection in water heating systems when oxygen diffusion is expected. In addition, chemical inhibitors should be regularly checked according to the manufacturer’s specifications.

Part 3: Corrosion by Flue Gases

The combustion of fuels produces flue gases containing contaminates that can condense into sulfuric, sulphurous, or hydrochloric acid droplets. The best way to prevent flue gas corrosion is to use more resistant material and reduce the number of contaminants in heater and boiler fuels.

Part 3 of the VDI2035 focuses on the gas-related corrosion of metallic materials within a hot water heating system. This section specifically refers to the exhaust gas or flue gas system. It is unrelated to system filling and water treatment. Although the VDI2035 does not cover this part extensively, it assumes that heating systems will follow previous regulations (specifically DIN EN 14336: 2005-01 and DIN EN 14868-2005), which states that heating system must be flushed and cleaned before the installation and usage of a water-based heating system.

Is Germany the only country to use VDI2035?

Austria and Switzerland have developed similar regulations, HöNORM IN 5195-1 and SWKI BT201-01. All these water policy standards recommend the non-use of inhibitors. In many countries worldwide, hot-water boilers use alkaline chemicals for water treatment to prevent corrosion and fouling inside heating systems. However, depending on the type of pipes used, such as copper or aluminium, chemical reactions could be very serious under alkaline water conditions. Therefore, depending on the heating systems, the use of inhibitors can become very complicated. Hence moving away from their usage in several European countries.

It is also important to note that while many European appliance manufacturers base their own water treatment guidance on the VDI2035, this water treatment standard is not a recognised guideline in the UK. Consequently, many UK-based water and heating specialists are concerned that the VDI2035 recommendations may not be suited for UK systems.

However, since the VDI2035 is considered a corrosion preventative system, compared to a reactionary one commonly used in the UK, there is no doubt that it is far more effective, less costly in the long term, and significantly more effective environmentally friendly.

Why is the VDI2035 an important standard in water heating?

Many chemical engineers, particularly water and heating specialists, have come to accept that using chemicals for corrosion inhibitors inside water heating boilers has become unnecessary to prevent malfunction and system corrosion.

The VDI2035 is based on strong scientific evidence to develop a water-heating system in which corrosion, blockages, scale, and damage to pumps, seal and gaskets is unlikely. The methods recommended in the VDI2035 are based on natural science rather than the use of unnecessary and potentially harmful chemicals.

Why do I need the VDI2035?

Ultimately, the guidelines developed in the VDI2035 have helped significantly reduce the damage caused in traditional water heating systems. Such damage frequently reduces the lifespan of expensive equipment. In addition, by following the guidelines recommended in the VDI2035, a water heating system becomes much more environmentally friendly. Anything that eliminates the use of unnecessary chemicals and the need for regular equipment replacement. This system will ultimately save your clients a lot of stress and money. Lower heating bills and reducing the need to maintain their boiling system regularly are sure to be crowd-pleasers.