How to mark pipework correctly to DIN 2403
DIN 2403 defines how pipes are marked by their conveyed medium using colour, text and a flow-direction arrow. This guide explains the colour groups, the mandatory arrow, correct label spacing and how to keep marking legally compliant.
View pipe markersWhat does DIN 2403 cover?
DIN 2403 Identification of pipelines according to the conveyed medium assigns each medium a base colour and defines how that colour is shown together with the substance name and a flow-direction arrow. The goal is that anyone on site can see at a glance what flows through a line and in which direction.
Marking is usually applied with self-adhesive pipe markers or warning labels that combine the plain-text substance name, the colour field of the group and the arrow. For hazardous substances, GHS/CLP hazard marking is added on top.
Which colour belongs to which medium?
DIN 2403 sorts media into groups with defined base colours. The base colour shows the state or type of substance, while an additional colour can flag special properties such as high temperature or hazard.
- Base colour = substance group, clearly visible as a continuous colour field.
- Additional colour (e.g. red for hazard) as a narrow stripe or field.
- Substance name in plain text to prevent any mix-up.
- GHS pictograms added where hazardous substances require them.
How are the arrow and labels applied?
The flow-direction arrow is mandatory and shows unambiguously which way the medium travels. It sits in the base or contrast colour directly next to or on the substance name so that text and arrow form one unit.
Marking is repeated at every relevant point: at valves, branches, before and after wall penetrations, and within sight along long straight runs. A common rule of thumb is a spacing of about 10 to 15 metres so at least one marker is visible from any position.
How to mark in a durable, compliant way?
Compliant means: permanently adhered, resistant to the medium and environment, and clearly legible. Occupational safety and hazardous substances regulations require that employees can reliably identify pipes and their contents.
- Choose material by environment: UV- and weather-resistant films outdoors.
- Chemical- and temperature-resistant markers on hot or aggressive lines.
- Check legibility and adhesion regularly and document it.
- Update the marking immediately when the medium in a line changes.
Frequently asked questions
Is DIN 2403 marking legally required?
DIN 2403 itself is a standard, not a regulation. Occupational safety and hazardous substances law make clear pipe identification mandatory, and DIN 2403 is the recognised state of the art for it.
Must there always be a flow-direction arrow?
Yes, the arrow is a fixed part of the marking. It shows the flow direction unambiguously and is especially important at branches and valves.
How often should pipe markers be repeated?
A common rule of thumb is every 10 to 15 metres, plus at valves, branches and wall penetrations. What matters is that at least one marker is visible from any position.
What colour is a water pipe under DIN 2403?
Water is assigned to the group with the base colour green. Additions indicate special properties such as temperature or treatment.
Marking pipework to standard?
We supply pipe markers and labels to DIN 2403 with colour group, substance name and flow-direction arrow - durable and compliant.
Standard-compliant
Markers to DIN 2403 with the correct colour group.
Arrow included
Flow direction clearly identified.
Durable
UV-, chemical- and temperature-resistant films.
Expert advice
We help with colour group and label size.