Corrosion of Copper alloy fittings in a combined Plastic/Metal in-stallation for hot drinking water

摘要

A household installation for drinking water was analysed for the water quality after an incident concerning the water distribution system in the city. Chemical analysis showed very high levels of lead in the hot water circulation system. The installation was made from multi-layer-pipes, the hot water tank from stainless steel, no obvious source of lead could be determined. After a thorough cleaning of the piping system and the tank the lead levels rose again after short time.Water samples and samples of the pipe connectors made from different copper al-loys were taken during an inspection of the building. Results for water analysis and metallographic investigations of the samples are given. Close examination of the connectors showed selective corrosion along the grain boundaries for the connectors made from brass but not for the connectors made from gun metal.The lead found in the hot drinking water war released from the brass connectors. Obviously the contact time of the water with the metal surfaces in the system investi-gated was much longer as the contact times used for the evaluation of metallic mate-rials according to EN 15664-1. The standards for the dimensioning of hot water circu-lation systems available are outdated and do not consider retention time in the sys-tem but are driven by maximum availability of hot water at any time.