If you are looking to build or buy a house, especially in a humid or flood-prone area in the basement, an important aspect of your home is the plumbing.
A perimeter or French drain is a drainage ditch lined with gravel to drain water from a certain area as a bottom. While French drains were made with spacer plates, nowadays they are usually made with perforated plastic pipes, which can carry a larger volume of water and allow water to flow along the pipes. You can find perimeter drainage services via johngplumbing.com/plumbing-services/drain-and-sewer-cleaning/.
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The purpose of perimeter drainage around your base is to draw in water that would otherwise be around the base and drain in, possibly creating a very wet basement or crawl space. Properly designed perimeter drainage should be at a level lower than the foundation to prevent capillary action from pulling water up and through the walls.
An inner perimeter can also be used, which is also installed around the inner perimeter of the cellar. The idea behind internal drainage is that, unlike the outer perimeter, no dirt or debris is clogging it so you don't have to throw it away after a few years of use and because it's internal, all repairs are easy to make.
Many of these internal drains are just gaps around the basement walls, allowing water from leachate to collect and moisture to drip off the concrete walls.