*4.2. Potential for Rainwater Reuse in Poland*

It was estimated that, at current costs, under Polish conditions rainwater provision for non-potable uses is nearly twenty times cheaper than purchase from public supply, considering only energy consumption for the harvesting system, but excluding initial investment [44]. Climatic conditions in Poland would generally enable effective functioning of such systems, as confirmed by the results of simulation studies [63]. Although it was shown that under the current conditions investment costs are much lower than they had been assessed a few years ago, the financial sustainability of such choices should be evaluated on a case-by-case basis. The introduction of local incentives and fee reduction is without doubt a strong boost to the adoption of these systems in new developments, improving the economic aspects.

In Poland, approximately 85% of potable water comes from surface waters, and requires subsequent purification processes [64]; water supply infrastructure was designed in the 1970s and 1980s to meet the increasing water demand of intensively developing, water-absorbing industries, as well as the high water consumption in the residential sector, and still has considerable reserve capacity. Limiting flow in these networks could require measures to detect and counteract possible secondary contamination during longer in-pipe residence, if this and other water savings solutions were to be adopted on a large scale. Improved systems for in-line detection of waterborne pollutants, such as the application of drinking water contaminant warning systems that are currently being developed may be of use [65]. From this point of view, drastically reducing consumption of water from existing municipal systems may not always be desirable, however, as the price of tap water will become higher; due to the need to modernize the existing treatment and distribution systems, the introduction of mixed supply schemes may become appealing.
