Turn off the water at the main stop tap if you can do so safely, and move valuables away from the leak. If water is near electrical outlets, switch off power only if it is safe; for a gas smell, leave immediately and contact your gas distributor or 000 if there is immediate danger. Call a licensed plumber, explain the problem and ask about their emergency call-out fee, hourly rate and likely arrival time before work begins. Keep photos, invoices and notes, as your insurer may request them, but coverage depends on your policy.