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:Slovak term: [[Slovenský termín]]
# A drainage trench is a drain that is surrounded by stone or other inert material used as a soakaway for liquid dispersion (WHO 1992).
# An excavation, cut below the ground surface for the purpose of installing a drain or drainage system (World Plumbing Council Working Group 2008).

==Explanation==
Soil pores eventually become clogged by effluent from pits or drainage trenches. This may
reduce or even stop infiltration through the soil. The soil type and the level of the
groundwater table relative to the liquid in the pit or trench affects the rate at which liquid
infiltrates from pits and drainage trenches. Opinions vary regarding whether the base or
sidewalls of drainage trenches or pits are the primary areas through which infiltration
takes place. The effluent from pits and drainage trenches may contain pathogens and
chemical substances that could contaminate drinking-water supplies. Because of their
comparatively large size, protozoa and helminths are rapidly removed by the straining
action of the soil, but bacteria and viruses are more persistent. Effluent passing through
unsaturated soil above the groundwater table is purified by filtration and by biological and
adsorption processes. Filtration is most effective in the organic mat where the soil pores
are clogged. The passage of pollutants from a new pit or drainage trench reduces as the
pores become clogged. Unsaturated sandy or loamy soil below a pit or drainage trench is
likely to provide an effective barrier to groundwater pollution (WHO 1992).
A drainage trench is required when a drain for a single domestic dwelling is installed below
ground between the dwelling and the authority’s connection point (World Plumbing
Council Working Group 2008).

==Example==
A drainage trench is an excavation, cut below the ground surface. The base of the drainage
trench must be constructed with grades or falls. The grades enable the gravity forces in the
drainage system to work. The grades are calculated by taking into account the hydraulic
loads and size of the drain pipe.
A drain must be installed with deeper than a minimum cover to protect it from future
damage. The depth of the cover required is specified in plumbing codes. A trench is also
used to protect other easily damaged and services, such as water supply, gas supply, power
lines and data lines (World Plumbing Council Working Group 2008).

==References==
* WHO (1992) [http://www.who.int/water_sanitation_health/hygiene/envsan/onsitesan/en/ A guide to the development of on-site sanitation]

==Links==
* [http://apps.who.int/thelexicon/ WHO — The Health and Environment Lexicon]

[[Category:EN]]

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	* [http://apps.who.int/thelexicon/ WHO — The Health and Environment Lexicon]		* [http://apps.who.int/thelexicon/ WHO — The Health and Environment Lexicon]

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Drainage trench - História úprav

Vrut na 10:24, 23. júl 2014

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