He also developed a float valve system for the flush tank. Obtaining the patent for it in 1778, he began making toilets at a workshop in Denmark Street, St Giles. The design was arguably the first practical non-manual flush toilet, and production continued well into the 19th century, used mainly on boats. Thomas Bowdich, an English traveller, visited Kumasi, capital of the Ashanti Empire in 1817 and mentioned that majority of the houses in the city especially those near the king's palace included indoor toilets that were flushed with gallons of boiling water.