

It’s irresponsible; the rain gutters are for clean surface water wash off and drain freely into water courses, rivers, lakes etc untreated; they’re totally separate from the sewers even though both systems run under the roads. Organic liquids should be disposed off via the sewage system - so down a toilet or a sink - where the water should be treated before being released back into the water table.
If everyone were disposing of contaminated water in the surface drainage system we’d be in big trouble.
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.