Down pipes

The volume of water from four down pipes leading into one is too much & this could lead to overflowing gutters which may enter into the internal areas and cause moisture damage to the ceiling, walls, electrical items and other building materials.
As per the Building Code of Australia, there must be a downpipe installed for each 12 metres of guttering.  A plumber will need to install more down pipes to divert the water into the storm water drainage system.