Copper corrosion in residential plumbing installations can lead to an increase in copper concentration in drinking water as well as to leakages. Central water treatment steps such as pH‐adjustment or dosages of phosphate‐based inhibitors are measures in reducing copper corrosion. Especially phosphate in drinking water is believed to work as a corrosion inhibitor, but it is currently uncertain as to how this inhibitor works. In some cases the phosphate dosage aggravated the copper corrosion. The mechanisms are not yet clear and the influence of phosphate and pH remain a question to be answered. The results of a German Gas and Water Works Association (DVGW) research project on copper corrosion are presented as follows. The influence and the mechanisms of decarbonisation, deacidification and phosphate dosing on copper release in residential plumbing installations were studied in pipe rig experiments according to the German standard DIN 50931‐1. It shows that an increased pH‐value can lead to a decrease in copper content and that a phosphate dosage can lead to both higher and lower copper concentrations.

corrosion of copper remains a question to be answered. Using standardised on-site corHannover, Germany rosion tests (DIN 50931-1) with virgin copper pipes softening/decarbonisation has decreased the copper concentration. Two effects of phosphate on copper corrosion were noticed: Phosphate dosing decreased the copper oxidation and resulted in lower copper concentration in water. Likewise phosphate hindered the precipitation of cupric ions, which prolonged the existence of copper in water and resulted in a higher copper concentration. As a consequence, dosing phosphate can decrease or increase the copper corrosion, this depends on which effect is dominating.

The present study describes examinations of growth rate of calcium carbonate using seed crystals of different sizes in the range of 10 to 50 μm at concentrations in the range of 5 to 50 g·L−1. The rate constant related to the crystal surface per volume was found to be independend of the crystal size. The effect of temperature on the rate constant was described using the Arrhenius equation. The use of suspension of lime as precipitating agent leads to decrease of the rate constant compared to lime water. This effect can be explained by the dissolution of suspended calcium hydroxide particles. Using the presented conditions (SI0 = 2.8), no impact of iron and manganese ions was observed.

This article describes a method for an accelerated, controlled and reproducible build-up of limescale in potable water systems. The concept of this method is to systematically generate water with a high calcium carbonate precipitation potential (CCPP) by CO 2 -enrichment, hardening with CaCO 3 followed by CO 2 -desorption. Water with a CCPP of about 100 mg/L CaCO 3 led to the intended calcification on inner steel tube surfaces in a simplified test plant. The limescale built-up was performed at ambient temperature. The procedure is an enabler for validation, verification and comparison of both the efficiency of decalcification methods, as well as scale-preventing methods under comparable and defined conditions. An economical and time efficient calcification method has been developed that provides solid calcite deposits of reproducible thickness and characteristics. The method can be used for studies with all water-carrying systems in household, public transportation or industrial applications.