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Reservoirs to store water may have been built at Lea Bridge from as early as the fifteenth century.
Reservoirs constructed at Lea Bridge in the 1830s and 1840s were designed for storage and 'settling' - allowing particles in the water to sink to the bottom of the reservoir.
The first successful sand filter bed was introduced in 1829 at the Chelsea Waterworks. By 1834, Parliament required firms to incorporate filter beds into all new works. The 1852 Metropolis Water Act subsequently required that only filtered water could be supplied in London.
The construction of a sequence of new filter beds and the adaptation of existing storage and settling reservoirs began at Lea Bridge from 1852-3, beginning with the Number One Essex Beds.
Sand filter beds use biological processes to clean the water. A gelatinous film forms on the top layer of sand which traps foreign matter, reducing the bacteria in the water by up to 99%.
The performance of slow sand filters gradually degrades, reducing the rate of flow through the filter. The top layer of sand must either be periodically scraped away to reveal clean sand beneath, or the sand layer can be stirred up ('wet harrowing'), suspending solids in the water, which can then be drained away.
Two aqueducts were constructed.
The first aqueduct, constructed in 1829, conveyed water taken from below the weir at Lea Bridge to the waterworks at Old Ford. The aqueduct travelled southwards, parallel with the Hackney Cut.
The second aqueduct constructed in 1852-3 brought water to Lea Bridge from the Old Coppermill and the reservoirs constructed there. The aqueduct was subsequently extended further north, first to Tottenham Mills and then Fields Weir, Enfield.
An Economic History of London 1800-1914. Professor Michael Ball and David T. Sunderland