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The Evolution of Drainage Systems in the UK: From Combined to Separate Systems
Wednesday 5th February 2025
Carl O'Boyle BSc MRICS FCIOB MFPWS
In the United Kingdom, the design of drainage systems has evolved over time. Properties built in the 1930s often featured combined drainage systems, where both surface water (rainwater) and foul water (sewage) were conveyed through the same pipes to treatment facilities. This approach was common in earlier constructions.
The shift towards separate drainage systems, distinguishing between surface water and foul water, became more prevalent in properties constructed after 1970. In these modern systems, surface water is typically directed to natural watercourses or soakaways, while foul water is sent to sewage treatment plants.
Therefore, it's likely that a 1930s property would have a combined drainage system, unless it has been updated to a separate system in subsequent years.
