That is not correct - the surface drainage system should be regarded as separate from the sewage system, even though both run under the roads. There is the surface water system and the foul water system. It’s true that in some places surface drainage may go into the sewage system but that is the exception rather than the rule. Surface drainage is usually designed to move as rapidly as possible into nearby fresh water to prevent flooding.
Surface drainage water is allowed to drain freely into water courses, rivers and lakes, completely untreated. The sewage system is for contaminated water (from toilets and sinks etc) and is designed to go to treatments plants where it SHOULD be treated. It is true that that treatment is not happening, and when there are storms the sewage system can be overrun with water companies currently getting away with dumping contaminated sewage into the rivers which is a scandal.
I’ve seen plenty of news reports say that combined sewers are nearly ubiquitous, but now when I’m googling it, I’m seeing some sites back that up, and other sites saying it’s only about a fifth of the country, so I don’t know which to trust. I can see Ofwat and some of the water companies say that the rules changed (potentially in 1991) so new developments after that point have to use separate sewers, and that wouldn’t be that much of the UK, as most building is redevelopment of existing sites where existing sewers can be reused, rather than new developments, and most things haven’t been rebuilt in the last thirty years, so I’d be surprised if it was 80% separate if it’s only new stuff using it, but less surprised if it’s just the Victorian sewers that are combined (and areas that still use Victorian sewers that have been spilling foul water into waterways) and things have been gradually switched over for more than a century. Do you have a source that explains the incompatible figures?
That is not correct - the surface drainage system should be regarded as separate from the sewage system, even though both run under the roads. There is the surface water system and the foul water system. It’s true that in some places surface drainage may go into the sewage system but that is the exception rather than the rule. Surface drainage is usually designed to move as rapidly as possible into nearby fresh water to prevent flooding.
Surface drainage water is allowed to drain freely into water courses, rivers and lakes, completely untreated. The sewage system is for contaminated water (from toilets and sinks etc) and is designed to go to treatments plants where it SHOULD be treated. It is true that that treatment is not happening, and when there are storms the sewage system can be overrun with water companies currently getting away with dumping contaminated sewage into the rivers which is a scandal.
I’ve seen plenty of news reports say that combined sewers are nearly ubiquitous, but now when I’m googling it, I’m seeing some sites back that up, and other sites saying it’s only about a fifth of the country, so I don’t know which to trust. I can see Ofwat and some of the water companies say that the rules changed (potentially in 1991) so new developments after that point have to use separate sewers, and that wouldn’t be that much of the UK, as most building is redevelopment of existing sites where existing sewers can be reused, rather than new developments, and most things haven’t been rebuilt in the last thirty years, so I’d be surprised if it was 80% separate if it’s only new stuff using it, but less surprised if it’s just the Victorian sewers that are combined (and areas that still use Victorian sewers that have been spilling foul water into waterways) and things have been gradually switched over for more than a century. Do you have a source that explains the incompatible figures?