Influence of organic materials on water intended for human consumption - Determination of odour and flavour assessment of water in piping systems; German version EN 1420:2016 / Note: This standard is part of the DVGW body of rules.

Standard Overview and Revision Background

EN 1420:2016 replaces EN 1420-1:1999, published in 1999. It is the European Committee for Standardization (CEN) standard for the impact of organic materials in contact with drinking water on the sensory properties of water. This standard was developed by CEN/TC 164, "Water Supply," with the French Standardization Association (AFNOR) serving as the secretariat.

Major technical updates in this revision include: the adoption of the TON (Odor Threshold Number) and TFN (Taste Threshold Number) determination methods specified in EN 1622; the introduction of a panel qualification procedure; alignment of the migration water preparation method with EN 12873-1; and expansion of the scope of application to include all organic products in contact with drinking water (including coatings and field-applied products).

Core Test Principles and Methods

The standard specifies a systematic approach for evaluating the impact of organic materials on the sensory properties of drinking water through migration testing. The testing process mainly includes three key stages: sample pretreatment, migration test implementation, and sensory property evaluation.

The migration test uses a surface area/volume ratio (S/V) control parameter. Different product categories have different S/V requirements: 40dm⁻¹ for pipes (DN/ID ≤ 80mm), 1.5dm⁻¹ for fittings and equipment, and 0.2dm⁻¹ for seals and adhesives.

Detailed explanation of key technical requirements

Test water preparation

The standard requires that the test water must be free of any detectable odor or taste. The free chlorine concentration of the chlorine test water should be controlled to (1.0±0.2) mg/l (as Cl₂) by adding sodium hypochlorite solution. Dechlorination with sodium thiosulfate or ascorbic acid solution is necessary, and the free chlorine content in the dechlorinated water should be less than 0.05 mg/l.

Specimen Pretreatment Procedure

Specimens undergo a rigorous pretreatment procedure prior to migration testing: first, rinse with tap water at a flow rate of 1-3 m/min for 60±5 minutes, then soak in the test water at 23±2°C for 24±1 hours, and finally rinse again for 2 minutes. This process is designed to simulate the initial rinse effect under actual use conditions.

Sensory Evaluation Method

Odor and taste are evaluated using the dilution method specified in EN 1622, using a serial dilution ratio of 2. The evaluation is conducted in a free-choice format, requiring a panel of at least five qualified assessors. The TON and TFN values for each sample are determined by calculating the geometric mean.

Panel Qualification and Management Requirements

The standard introduces a panel qualification procedure for the first time. Evaluators must pass two tests: individual TON determination and concentration ranking test. The reference substances used are 1-butanol (target concentration 250 μg/l) and methyl tert-butyl ether (MTBE) (target concentration 5.8 μg/l).

Panels require long-term performance monitoring, and the average deviation of individual assessors should not exceed 1.5 dilutions. It is recommended that a panel coordinator be appointed to be responsible for qualification management and result reliability control.

Implementation Key Points and Precautions

Product Category Testing Requirements

The standard specifies corresponding testing methods based on different product types: pipes are tested using the filling method, while fittings and equipment can use the filling or immersion method depending on their structural characteristics. For products installed on site, specimens must be prepared on dedicated test panels. For similar products with different specifications, only the product with the largest S/V ratio (smallest diameter) needs to be tested.

Migration Test Sequence Arrangement

Appendix B of the standard details the time sequence for multi-cycle migration tests. Cold water testing uses a 72-hour cycle, while hot water testing uses a 24-hour cycle. The test sequence design takes practical feasibility into account to ensure representative and comparable test results.

Quality Control Requirements

Each migration test must be conducted simultaneously with a blank test, using the same testing conditions and water to obtain a blank water sample. If the blank water sample exhibits a detectable odor or taste, the entire test is invalid and resampling is required.

Test Report Requirements

Chapter 13 of the standard specifies the information that must be included in the test report, including laboratory information, product identification, testing conditions, implementation details, and test results. For field-applied products, detailed information such as application conditions, curing process, and transportation conditions must also be recorded.

Test results should be reported as TON and TFN values, including data from three migration cycles and corresponding blank water sample results. All deviations from the standard method must be clearly stated in the report.

Importance and Future Applications of the Standard

The implementation of EN 1420:2016 provides a scientific basis for the selection and use of organic materials in water supply systems, helping to ensure the sensory quality of drinking water. This standard has been incorporated into the German DVGW specification system and is mandatory throughout Europe.

With increasing demands for drinking water quality, this standard has significant application value in areas such as compliance verification in the development of new pipe materials, material selection in water supply system renovations, and the evaluation of the drinking water suitability of coatings and sealants. The implementation of the standard will promote the standardized development of materials and technology in the water supply industry.