I'M IN THE MIDDLE OF BUILDING A NEW EXTENSION ON THE HOUSE, AND HAVE PUT A NEW 6 WAY INSPECTION MANHOLE TO CONNECT VARIOUS SOIL PIPES IN THE BACK GARDEN. WHAT I NEED TO KNOW IS IF, I CAN RUN ANOTHER PIPE FROM A RAINWATER GULLEY TO JOIN INTO THIS NEW 6 WAY INSPECTION UNIT AS I HAVE 2 SPARE WAYS LEFT....