A Buchan trap (alternative names: ''Bristol interceptor'', ''interceptor trap'' and ''disconnecting trap'') is a device made from

fireclay Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick. The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of alumin ...

located in a domestic sewer pipe to prevent odours entering the pipe from the public sewer and thus the property served by the drain. The trap uses a water seal to prevent air from the public sewer entering the property. In the days before individual plumbing fittings were separately trapped, the smell from the public sewer could permeate the house. 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 an air-inlet/access point on the 'house' side. It is located below the ground level, but can be accessed through the air-inlet and sometimes a rodding hole.

Blockage risk

The Buchan trap will collect solids, sludge and waste that is not in suspension. In recent times, non-paper based wipes have posed a particular problem, according to most Water Authorities. The end result of these adverse conditions is a partial or complete blockage. The sewage/rainwater then backs up the pipe and exits 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 a type of building shared by multiple dwellings, typically with flats or apartments on each floor and with shared entrance stairway access. They are common on the British Isles, particularly in Scotland. In the medieval Old Town, i ...

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 recurring basis, such as annually.

History

The Buchan trap was devised in the 19th century to stop the flow of

sewer gas Sewer gas is a complex, generally obnoxious smelling mixture of toxic and nontoxic gases produced and collected in sewage systems by the decomposition of organic household or industrial wastes, typical components of sewage. Sewer gases may inclu ...

es also known as miasmas. It was believed that the disease

cholera Cholera is an infection of the small intestine by some strains of the bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea that lasts a few days. Vomiting and ...

was an airborne infection, not waterborne. 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. {{DEFAULTSORT:Buchan Trap Plumbing