This is obligated by the phenomenon called the shrinkage of the foundation. It is also necessary to process the contact places of wooden structural elements with aquifers with special means, in order to avoid putrefactive processes and mold formation. It is also important to choose high -quality pipes. The choice of pipes is a separate topic worthy of an entire article, so we will not focus on it in detail. We will only say that today there are many universal and inexpensive pipes on the market today, which can be considered a worthy option, PE100 for example.