Look for a Perth plumber who holds the appropriate Western Australian plumbing licence and can provide their licence details, written quote and proof of insurance. You can check licensing information through Building and Energy, part of the WA Department of Energy, Mines, Industry Regulation and Safety. Ask whether the work requires permits or compliance certificates, particularly for gas, drainage or major renovations. Compare a few itemised quotes and confirm who is responsible for arranging inspections and fixing any defects. For urgent leaks or sewage problems, use a licensed professional and take reasonable steps to limit water damage while you wait.