I’m mid-extension and my builder has installed four 9” square gullies to connect the rainwater down pipes to the drains. I’d prefer not to have these as they complicate my patio design. Can I simply remove them and connect the down pipes directly in to 110mm pipe using a reducer? Or are there building regs to comply with? For context all the other down pipes on my property appear directly connected without a gully. I have inspection chambers that can support rodding within a few meters of each gully if that helps.