District Water Main in Wakayama, Japan

The district water distribution network, constructed in 1981, had beeen the subject of frequent complaints from local residents regarding the discoloration of drinking water since the late 2000s. To address this issue, the district’s water authority conducted a trial installation of the corrosion prevention device Pipetector.

Based on the results of the trial, the water authority concluded that the device provided an effective solution for mitigating corrosion in the district’s ductile cast iron water mains and subsequently adopted it as its preferred corrosion-control measure. The details of the evaluation are described below.

To assess the effectiveness of Pipetector, the water authority and Japan System Planning Co., Ltd. carried out an iron concentration compariosn test using filtration.

Prior to the installation of Pipetector, a white filter was attached to a mud valve located at the terminal end of the water main. Water was then passed through the filter to evaluate the extent of red rust released from the pipeline. Following installation of the device, the same test was repeated under identical conditions after one month, two months, and five months.

After five months of operation, the discoloration observed on the filter had been significantly reduced. In addition, the iron concentration in the sampled water decreased from 110 mg/L to 21 mg/L, representing an 81% reduction compared with the pre-installation level.

These results confirmed that Pipetector effectively mitigated corrosion associated with red rust by suppressing its release into the water and promoting the conversion of existing red rust into black rust, an insoluble and passive protective layer.

Continued use of Pipetector is expected to further convert existing red rust into black rust, forming a durable layer of insoluble magnetite on the interior surface of the pipeline. This protective coating helps inhibit further corrosion and can substantially extend the service life of the water distribution system.