Destruction of underground reservoirs from within
From the end of the 19th century, underground collectors built of brick and stone. In large cities in Europe and America, such collectors operate to the present. Now they are more than 100 years old. Brick and stone were very resistant materials to the conditions of the underground sewer, but time takes its toll. Collectors are destroyed by abrasion by flow, soil movements, falling out of elements, poor exploitation.
In the first half of the 20th century, underground reservoirs began to built of concrete and reinforced concrete. As it turned out, concrete is not resistant to biological and gas corrosion, which destroy it at high speed above the low level. Reinforced concrete collectors began to lose their strength very quickly, and now many of them are in worse condition than brick ones.
In the cities of the former USSR, due to a bad operation, underground reservoirs are in a much worse state than in Europe.