For a minor blocked drain in Perth, remove visible debris and try a plunger, but avoid mixing or repeatedly using chemical drain cleaners, as they can damage pipes and create a hazard for plumbers. If several drains are slow, wastewater is backing up, or there is sewage, turn off water where practical and arrange a licensed plumber promptly. A blockage in the main sewer may involve the Water Corporation, while private pipes and internal drains are generally the property owner's responsibility. Check the Water Corporation website or ask your plumber who is responsible before approving non-urgent work.