Hinged valves

BRAMAH’S WATER CLOSET (1778)

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(Picture: Hugh Sainsbury/Crossness Engines Trust)

 

When the handle (right) of Bramah’s closet was pulled, the valve flap at the bottom of the pan opened and water was simultaneously released from the cistern above, flushing away waste and cleaning the valve at the same time. Pan and lever would have been enclosed within a wooden cabinet, typically mahogany.

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(Picture: © Science Museum/Science & Society Picture Library)

The diagram that illustrated Bramah’s patent shows the key components of his invention. F is the lever handle that, when pulled, opens both the hinged valve within the iron box B, and – via wires attached to secondary levers L – another valve at the cistern above (not shown). E is the spring that returns levers and valves to their closed positions after use.

 

At the point where water from the cistern enters through pipe H, a copper spreading plate fans out the flush around the pan for effective cleansing. Pipe G provides an overflow in case the upper valve fails and water overfills the pan; it has a bend holding a water seal, preventing sewer gases from bypassing the main flap valve and escaping into the room.

 

Another improvement not visible on this diagram is the position of the upper valve, at the level of the cistern, which ensured that the feed pipe beneath was empty of water and therefore would not freeze in very cold temperatures. A bend in the outflow pipe beneath the main valve held a water seal trap, creating another barrier preventing gases rising from the drain below and up through the pan.

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(Picture: The History Collection/Alamy)

 

A significant improvement on Cumming’s design, this model was expensive but popular: Bramah (pictured here) claimed to have sold 6,000 by 1797. Various tweaks were made over following years, including the introduction of ceramic pans in place of metal.

 

But problems remained, not least the twin issues of adequate piped water supply for the cistern, and removal of the waste flushed from the pan. Others were specific to Bramah’s design. The seal of the metal valve might leak, particularly if the spring became weak. One solution, devised in the 1790s, was to replace that flat valve with a hinged pan that tipped waste into an iron receiver; however, though this design was cheaper and more robust, pan and receiver also quickly became clogged with filth.

 

Bramah’s basic design remained popular over the following half-century or so, and production continued well into the 20th century.

 

See an original Bramah water closet at Crossness Engines in southeast London.