The very definition of "drainage" implies the natural or artificial removal of groundwater from the ground or from the surface of the earth. Therefore, there are several types of drainage.
Drainage of the site
If the soil on the site where the house is located is waterlogged, this brings some inconvenience to the life of the owners. The foundation of such a house may suffer, the basement is always damp and moldy, and nothing can be grown on the plot. Therefore, a whole system of underground canals-drains is made on the site, which help to drain water from the site. Drainage can be open, closed and backfill.
For open drainage, the perimeter of the site is dug in open ditches, the depth of which is about 0.7 m and the width of 0.5 m. The walls of the ditches are made beveled at an angle of about 30 °, the water flows into such ditches, and from them into a common gutter for all sites located near. Water flows into such ditches during rain or melting snow.
Closed, or deep drainage is done using pipes buried in the ground, through which excess ground moisture is taken into special wells. For this purpose, polyethylene pipes with perforations and holes are used, which are additionally wrapped with a layer of geotextile to avoid blockages.
Backfill drainage is in many ways similar to closed drainage, the only difference between them is that backfill drainage does not involve the use of pipes, and the trenches are filled with large rubble or broken brick. The upper part is covered with fine gravel fractions, and then all this is covered with soil. The backfill drainage silts up rather quickly, and therefore it is recommended to create a filtering layer of geotextile over the coarse gravel.
In all types of drainage, the channels must be sloped, since it is impossible to create pressure in the pipes, the water must leave by gravity. There should be no puddle and stagnation of water in the trenches - the very meaning of their laying is lost.
Drainage for indoor plants
There are very few flowers that like to have their roots constantly in water without air access and without the ability to remove excess moisture. Most houseplants prefer the following ratio - 35% water, 15% air and 50% solids in the soil. Therefore, in each pot, it is necessary to provide for the presence of holes for water drainage in the bottom and a layer of expanded clay balls or gravel so that the water flowing into the pan does not wash out all the earth from the pot.
All plant organs need respiration, and excess moisture displaces air from the soil, preventing the roots of such an opportunity. In the soil, where there is no air, but a lot of water, bacteria develop faster, which contribute to the rotting of the plant's root system.
For all indoor plants, drainage is required differently, since the degree of moisture tolerance is also different for all of them. For most, one hole in the center is enough, for some you have to make additional ones manually or look for a pot in which they are.