Descaling is the process of removing build up of scales caused by aging cast iron sewer lines. Over the years flakes from the cast iron can break off into the sewer line. The broken pieces eventually accumulate overtime and cause an obstruction in the line and snag any paper products that have been flushed down into you sewer. The more it builds up the higher the risk of your drains becoming clogged.
Descaling helps prevent future back-ups and it also prevents homeowners from having to replace their whole sewer lines, which would cost more to have done. Cast iron sewer pipes can last over 50 years, excluding factors that speed up deterioration, but unless your home is at least 50-60 years old, it’s likely that your sewer pipes are in fact in perfectly functional condition and don’t actually need replacing.