Very very naughty to run the stormwater to the sewer. Our council letterboxed everyone after the latest rains complaining their underground pumping hoozits couldn't keep up with it all. Not surprising, it rained for a week non-stop. Our backyard (and the house) started to fill up with frogs, of all things. I'm used to ants and spiders and millipedes and earwigs wandering around inside, maybe the occasional gecko, but frogs? Damn rain.
You NEED the sewer connected on a new house fyi, but not the stormwater. Our builder has given us helpful plans on how we should do it, but they just provide the holes in the gutter and leave it up to us to stick pipes in the holes and actually run the water to tanks/street.