Fitted some basin new taps & a new pop up waste today. Apart from checking for plumbing & waste leaks I always check that the overflow is working as well.
Combi boiler, so hot & cold at the same pressure, which was pretty high.
It surprised me how quickly the sink filled up. The overflow simply would not have coped with the flow of water from even one tap on full blast, let alone both. So it would be largely ineffective as an overflow - wouldn't prevent a flood if a tap was accidentally left on.
I wonder if sink & basin designers have thought about the flow rates now that hot water could be at mains pressure?