A flushing trough is a long

cistern A cistern (; , ; ) is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. To prevent leakage, the interior of the cistern is often lined with hydraulic plaster. Cisterns are disti ...

which serves several

toilet A toilet is a piece of sanitary hardware that collects human waste (urine and feces) and sometimes toilet paper, usually for disposal. Flush toilets use water, while dry or non-flush toilets do not. They can be designed for a sitting p ...

pans. It is designed to allow a shorter interval between flushes than individual cisterns. Flushing troughs were commonly used in places such as

school A school is the educational institution (and, in the case of in-person learning, the Educational architecture, building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most co ...

college A college (Latin: ''collegium'') may be a tertiary educational institution (sometimes awarding degrees), part of a collegiate university, an institution offering vocational education, a further education institution, or a secondary sc ...

s, public toilets,

factories A factory, manufacturing plant or production plant is an industrial facility, often a complex consisting of several buildings filled with machinery, where workers manufacture items or operate machines which process each item into another. Th ...

and public buildings where repeated use of the flushing cistern was required in a short period of time. Such troughs were used by local councils in the UK into the 1980s.

Background

Water byelaws in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

restricted the volume of water that could be used to flush WCs and

urinal A urinal (, ) is a sanitary plumbing fixture similar to a toilet, but for urination only. Urinals are often provided in men's public restrooms in Western countries (less so in Muslim countries). They are usually used in a standing position. ...

Water board A water board is a regional or national organisation that has very different functions from one country to another. The functions range from flood control and water resources management at the regional or local level (the Netherlands, Germany), ...

s typically required valveless siphonic cisterns that were designed to be "water waste preventers": these deliver a fixed volume of water on every flush and do not allow water to run into a WC pan continuously. A typical siphonic cistern is emptied completely when it is flushed, and can only be flushed again once it has refilled: the delay between flushes was found to be inconvenient in busy lavatories such as those in schools, factories or public conveniences. The flushing trough was designed to overcome this delay by allowing a fixed volume of water to be discharged from a larger cistern.

Development

The flushing trough was developed by Adamsez Limited and a

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...

was issued to MJ Adams in 1912 for a flushing trough that used the bell siphon flushing system. A further patent was issued in 1928 to AH Adams for a flushing trough that used the plate siphon mechanism, marketed as the 'Epic'. Advertisements by Adamsez stated that 25,000 were in use by 1939. Rival manufacturer Shanks obtained a patent for a modified version in 1935 which they marketed as the 'Alisa'.

Design

Flushing trough cisterns were usually made of

cast iron Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its car ...

or galvanised steel, but were also manufactured in fireclay and

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

, and could serve 2 or more toilets. The trough would typically span a row of cubicles, with an individual siphon and flush chain for each closet. The lever arm connecting the siphon plate to the flush chain was often fixed directly to a pivot on the siphon rather than the cistern, so the arrangement of the siphons was highly flexible: flush pipes could be fitted in the middle or side of the cubicles; flush chains could be arranged at the back or front of the trough, or through the bottom of the trough via a standpipe. Flushing troughs could also be concealed in ducts behind the wall of a range of WCs, with the flush chains linked to flush levers. Although flushing troughs generally proved reliable, a key disadvantage is that repair of one siphon requires all WCs served by the trough to be out of service.

Operation

Each siphon in a flushing trough is connected to its own timing box by a pipe.

Siphon A siphon (; also spelled syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted "U" shape, which causes a liquid to flow upward, abo ...

ic action is started in the same way as an ordinary flushing cistern. As the

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

is siphoned from the trough, water is also sucked from the timing box and the water level inside the box falls rapidly, with air drawn into the timing box through a 'snorkel' vent pipe. When the timing box has been emptied of water,

air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

flows through the timing box and into the siphon to break the siphonic action, stopping the flush. The timing box quickly refills with water through a hole in its side. The siphon is then ready to flush again. Up to seven siphons would be supplied by a single

ballcock A ballcock (also balltap or float valve) is a mechanism or machine for filling water tanks, such as those found in flush toilets, while avoiding overflow and (in the event of low water pressure) backflow. The modern ballcock was invented by Jos� ...

, which would refill the trough whenever the water level fell.

References

{{Plumbing Toilets