Bloke in the next flat combined his stacks, if it blocks at the bottom he would end up flushing his toilet into the shower/floor waste.
A lot of older stuff in this area had grey water (sink, laundry tub, bath) discharging into the street stormwater, not all houses have been redirected; young lovebirds up the street put an extra loo in their laundry and it emptied into the drain outside my house.
