What is the depth of the top cover and manhole of a septic tank that should be extended above the ground?

The correct depth for the top cover and manhole of a septic tank that should be extended above the ground is generally recommended to be 5 cm. This depth ensures that the access point is slightly elevated above the surrounding soil level, which helps prevent surface water from entering the septic tank and contaminating the system. By maintaining a height of about 5 cm, it allows for effective drainage and minimizes the risk of flooding around the tank area.

Other options may suggest greater heights that could unnecessarily complicate access or do not effectively serve the function of preventing water ingress. An extension of too much height, like 10 cm or more, can also create problems with ground maintenance and usability, as it may prove to be an obstacle or hinder proper functioning of the system.