The public sewage system in Germany is estimated to be over 400,000 kilometers in total. Some speak of 500,000 kilometers. Drainage of land from private properties is not even included in this gigantic length. They are estimated to be around another 1.5 million kilometers. Nobody knows exactly what this underground labyrinth is like. Rats probably know their way around best. Attempts are being made to record the total stock of, in particular, public attitudes in channel registers and channel databases. Ascertained damage to the sewer network is not the exception, but unfortunately the rule. One can speculate about the undetected damage. In Germany, the need for renovation has received a significant boost from the discussion about a self-regulation regulation.
In most cases, leakage is always thought of as discharge. But what about the liquids seeping in? The infiltration of infiltration water into the sewage system interferes with the smooth operation of sewage treatment plants. But the outflow (exfiltration) is also popularized. There are experts who speak of the filter effect of the soil. Or its self-cleaning power. Recent results are less encouraging. It is also premature to hope for biodegradability. There are cases where degradation actually increases toxicity. Singapore has started to close the pipeline network in order to keep the costs of drinking water treatment from contaminated groundwater under control. Leaky channels lead to cavities. Whole streets or track systems can collapse due to undermining. And of course an intact sewer network is not available for free. A trade-off between resource protection, technical feasibility and affordability. But the desire for an intact environment is increasing.