Buchan trap
A Buchan Trap is a device made from fireclay located in a domestic sewer
Sewerage refers to the infrastructure that conveys sewage. It encompasses receiving drains, manholes, pumping stations, storm overflows, screening chambers, etc. of the sanitary sewer...

 pipe to prevent vermin
Vermin is a term applied to various animal species regarded by some as pests or nuisances and especially to those associated with the carrying of disease. Since the term is defined in relation to human activities, which species are included will vary from area to area and even person to person...

 entering the pipe. The trap uses a water seal
Water seal
Water seal may refer to:*Liquid trap seal in plumbing traps*Underwater seal in pleural drainage apparatuses*Waterproofing...

 to prevent rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s and mice
-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...

 climbing any further along the pipe. Waste flows from the house through a U-bend in the trap. This means that there is always water in the pipe preventing the passage of anything from the other direction. The device is a large clay U-bend with air-inlets and vents at the top. It is located below the ground level, but can be accessed through the air-inlet and a rodding hole. This hole allows drain rods to unblock anything located at the bottom of the U-bend.

Blockage risk

The Buchan trap will collect solids, sludge and waste that is not in suspension and, over time, can clog up. The overflow will back up the pipe and exit from the lowest connected appliance (sink, bath, dish washer, washing machine, etc.). This can be a significant problem in multi-level dwellings (e.g. tenement
A tenement is, in most English-speaking areas, a substandard multi-family dwelling, usually old, occupied by the poor.-History:Originally the term tenement referred to tenancy and therefore to any rented accommodation...

s) where those at the lowest level will receive all the waste waters from those above. They should be checked, and cleaned if required, on a regular basis (say annually).

Traps of this type are widely believed by plumbers to stop the entry of rats but rats are good swimmers and can easiler pass through the short flooded section of the trap. The purpose of these traps (as this article says) was to help prevent sewer air entering houses - foul air was thought by the Victorians to be the source of disease .


The Buchan trap was devised in the 19th century to stop the flow of sewer gas
Sewer gas
Sewer gas is a complex mixture of toxic and non-toxic gases produced and collected in sewage systems by the decomposition of organic household or industrial wastes, typical components of Sewage....

es also known as miasmas
Miasma theory of disease
The miasma theory held that diseases such as cholera, chlamydia or the Black Death were caused by a miasma , a noxious form of "bad air"....

. It was believed that the disease cholera
Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...

was an air born infection, not water born. The Buchan trap is normally found in the bottom of manholes or drop-shafts. It normally denotes the end point of the domestic property's sewer before it joins the main public sewer.

External links

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